Chapter: Nervous System; Topic: Cranial Nerves; Subtopic: Parasympathetic Pathways to Lacrimal Gland
Keyword Definitions:
Lacrimal gland: Exocrine gland that secretes tears to lubricate and protect the eye.
Parasympathetic supply: Autonomic fibers responsible for secretory stimulation of glands.
Greater petrosal nerve: A branch of the facial nerve that carries parasympathetic fibers to the lacrimal gland.
Pterygopalatine ganglion: A parasympathetic ganglion where preganglionic fibers from the facial nerve synapse before reaching the lacrimal gland.
Lead Question - 2014
Parasympathetic supply to lacrimal glands are passed through?
a) Lesser petrosal nerve
b) Chorda tympani
c) Greater petrosal nerve
d) Lingual nerve
Explanation:
The parasympathetic fibers to the lacrimal gland originate from the superior salivatory nucleus of the facial nerve. They travel via the greater petrosal nerve, synapse in the pterygopalatine ganglion, and then reach the lacrimal gland through the zygomatic and lacrimal nerves. This pathway controls tear secretion. Hence, the correct answer is c) Greater petrosal nerve.
1) Which ganglion is involved in the parasympathetic pathway to the lacrimal gland?
a) Ciliary ganglion
b) Otic ganglion
c) Pterygopalatine ganglion
d) Submandibular ganglion
The pterygopalatine ganglion (also called sphenopalatine) is where the preganglionic parasympathetic fibers from the greater petrosal nerve synapse. Postganglionic fibers then reach the lacrimal gland via the zygomatic branch of the maxillary nerve. Hence, the correct answer is c) Pterygopalatine ganglion.
2) The greater petrosal nerve is a branch of which cranial nerve?
a) Trigeminal
b) Facial
c) Glossopharyngeal
d) Vagus
The greater petrosal nerve arises from the facial nerve (cranial nerve VII) at the geniculate ganglion. It carries preganglionic parasympathetic fibers to the pterygopalatine ganglion, which later innervate the lacrimal and nasal glands. Hence, the correct answer is b) Facial nerve.
3) Which nerve carries postganglionic fibers to the lacrimal gland?
a) Zygomatic nerve
b) Auriculotemporal nerve
c) Lingual nerve
d) Nasociliary nerve
After synapsing in the pterygopalatine ganglion, postganglionic fibers travel via the zygomatic nerve (branch of V2) and join the lacrimal nerve (branch of V1) to reach the lacrimal gland. Hence, the correct answer is a) Zygomatic nerve.
4) Which cranial nucleus gives origin to fibers supplying the lacrimal gland?
a) Inferior salivatory nucleus
b) Superior salivatory nucleus
c) Edinger-Westphal nucleus
d) Dorsal motor nucleus of vagus
The superior salivatory nucleus of the pons provides preganglionic parasympathetic fibers that travel through the facial nerve and greater petrosal nerve to reach the lacrimal gland, promoting tear secretion. Hence, the correct answer is b) Superior salivatory nucleus.
5) (Clinical) Damage to the greater petrosal nerve results in?
a) Loss of taste
b) Dryness of eyes
c) Hyperlacrimation
d) Facial palsy
Injury to the greater petrosal nerve disrupts parasympathetic innervation to the lacrimal gland, leading to dryness of the eye due to reduced tear secretion. This may occur in facial nerve lesions proximal to the geniculate ganglion. Hence, the correct answer is b) Dryness of eyes.
6) (Clinical) A lesion at the geniculate ganglion affects which functions?
a) Lacrimation and taste
b) Hearing only
c) Facial sensation
d) Eye movements
A lesion at the geniculate ganglion affects both lacrimation (greater petrosal nerve) and taste (chorda tympani). Patients may present with dry eyes and loss of taste on the anterior two-thirds of the tongue. Hence, the correct answer is a) Lacrimation and taste.
7) (Clinical) Which symptom indicates greater petrosal nerve damage in facial palsy?
a) Loss of corneal reflex
b) Decreased lacrimation
c) Hyperacusis
d) Vertigo
In facial palsy affecting the segment proximal to the greater petrosal nerve, decreased lacrimation occurs due to interruption of parasympathetic fibers to the lacrimal gland. Hence, the correct answer is b) Decreased lacrimation.
8) (Clinical) A patient with Bell’s palsy complains of dry eyes. Which structure is likely involved?
a) Chorda tympani
b) Greater petrosal nerve
c) Stapedius branch
d) Temporal branch of facial nerve
Dry eyes in Bell’s palsy suggest involvement of the greater petrosal nerve due to interruption of parasympathetic supply to the lacrimal gland. This differentiates proximal from distal facial nerve lesions. Hence, the correct answer is b) Greater petrosal nerve.
9) (Clinical) Which condition may cause excessive tearing (epiphora) despite normal nerve function?
a) Blocked nasolacrimal duct
b) Facial nerve palsy
c) Damage to pterygopalatine ganglion
d) Geniculate ganglion lesion
Excessive tearing, or epiphora, usually results from a blocked nasolacrimal duct, preventing proper tear drainage into the nasal cavity. The parasympathetic pathway remains intact. Hence, the correct answer is a) Blocked nasolacrimal duct.
10) (Clinical) Which condition is characterized by dry eyes and mouth due to autoimmune destruction of lacrimal and salivary glands?
a) Myasthenia gravis
b) Sjögren’s syndrome
c) Bell’s palsy
d) Sarcoidosis
Sjögren’s syndrome causes autoimmune destruction of lacrimal and salivary glands, leading to dry eyes (xerophthalmia) and dry mouth (xerostomia). Parasympathetic pathways remain intact, but glandular tissue is damaged. Hence, the correct answer is b) Sjögren’s syndrome.
Chapter: Neuroanatomy; Topic: Brainstem Circulation; Subtopic: Arterial Supply of the Medulla Oblongata
Keyword Definitions:
Medulla oblongata: The lowest part of the brainstem, controlling vital functions like breathing, heart rate, and reflexes such as swallowing and coughing.
Vertebral artery: A branch of the subclavian artery that ascends through the cervical vertebrae to supply the brainstem and cerebellum.
Anterior spinal artery: Formed by branches of the vertebral arteries, supplying the anterior two-thirds of the medulla and spinal cord.
Basilar artery: Formed by the union of the two vertebral arteries, supplying the pons and upper medulla.
Posterior cerebral artery: A branch of the basilar artery that supplies the midbrain and occipital lobes but not the medulla.
Lead Question – 2014
Medulla is supplied by all except?
a) Basilar artery
b) Anterior spinal artery
c) Vertebral artery
d) Posterior cerebral artery
Explanation:
The medulla oblongata is supplied mainly by the vertebral arteries, anterior spinal artery, and posterior inferior cerebellar artery (PICA). The basilar artery contributes minimally to the upper medulla. However, the posterior cerebral artery supplies the midbrain and occipital lobes but does not supply the medulla. Hence, the correct answer is d) Posterior cerebral artery. This vascular arrangement is vital for maintaining vital autonomic functions.
1) Which artery forms the anterior spinal artery?
a) Vertebral artery
b) Basilar artery
c) Posterior inferior cerebellar artery
d) Posterior spinal artery
Explanation: The anterior spinal artery is formed by branches of the vertebral arteries near their junction at the medulla. It runs along the anterior median fissure and supplies the anterior two-thirds of the spinal cord and medulla. Hence, the correct answer is a) Vertebral artery.
2) The posterior inferior cerebellar artery (PICA) is a branch of which artery?
a) Basilar artery
b) Vertebral artery
c) Posterior cerebral artery
d) Internal carotid artery
Explanation: The PICA arises from the vertebral artery before it merges into the basilar artery. It supplies the dorsolateral medulla and inferior part of the cerebellum. Its occlusion results in lateral medullary (Wallenberg’s) syndrome. The correct answer is b) Vertebral artery.
3) Occlusion of which artery causes medial medullary syndrome?
a) Anterior spinal artery
b) Posterior spinal artery
c) Basilar artery
d) Posterior inferior cerebellar artery
Explanation: Medial medullary syndrome occurs due to occlusion of the anterior spinal artery. It affects the pyramids, medial lemniscus, and hypoglossal nerve, leading to contralateral hemiplegia, loss of proprioception, and ipsilateral tongue paralysis. Hence, the correct answer is a) Anterior spinal artery.
4) Which artery does not directly contribute to the blood supply of the medulla?
a) Vertebral artery
b) Posterior cerebral artery
c) Basilar artery
d) Anterior spinal artery
Explanation: The posterior cerebral artery supplies the midbrain, thalamus, and occipital cortex, but not the medulla. The vertebral, basilar, and anterior spinal arteries all supply portions of the medulla. Hence, the correct answer is b) Posterior cerebral artery.
5) A patient presents with hoarseness, loss of gag reflex, and contralateral body sensory loss. Which artery is most likely affected?
a) Anterior spinal artery
b) Posterior inferior cerebellar artery
c) Basilar artery
d) Posterior cerebral artery
Explanation: These are classic features of lateral medullary (Wallenberg’s) syndrome due to occlusion of the PICA. It affects the nucleus ambiguus, spinal tract of the trigeminal nerve, and spinothalamic tract. Hence, the correct answer is b) Posterior inferior cerebellar artery.
6) The basilar artery is formed by the union of which arteries?
a) Internal carotid arteries
b) Vertebral arteries
c) Anterior spinal arteries
d) Posterior cerebral arteries
Explanation: The basilar artery is formed by the union of the two vertebral arteries at the level of the pontomedullary junction. It ascends on the ventral surface of the pons and gives off branches to the pons, cerebellum, and inner ear. Hence, the correct answer is b) Vertebral arteries.
7) A 60-year-old man presents with tongue deviation to one side and contralateral hemiplegia. The lesion involves which artery?
a) Basilar artery
b) Anterior spinal artery
c) Posterior inferior cerebellar artery
d) Posterior cerebral artery
Explanation: The symptoms indicate medial medullary syndrome due to occlusion of the anterior spinal artery. It damages the hypoglossal nerve, pyramid, and medial lemniscus. Tongue deviation occurs ipsilaterally, and contralateral weakness occurs due to corticospinal tract involvement. Correct answer: b) Anterior spinal artery.
8) Which of the following arteries supplies the dorsal medulla including the gracile and cuneate nuclei?
a) Posterior spinal artery
b) Anterior spinal artery
c) Vertebral artery
d) Basilar artery
Explanation: The posterior spinal arteries supply the dorsal medulla, particularly the gracile and cuneate nuclei. These arteries arise from either the vertebral arteries or posterior inferior cerebellar arteries. Their occlusion leads to sensory loss for fine touch and proprioception. Hence, the correct answer is a) Posterior spinal artery.
9) A stroke involving the vertebral artery may present with which of the following symptoms?
a) Contralateral limb paralysis and ipsilateral facial weakness
b) Dysphagia, hoarseness, and ataxia
c) Aphasia and hemianopia
d) Facial numbness and upper limb weakness
Explanation: Vertebral artery occlusion can cause lateral medullary syndrome with dysphagia, hoarseness, ataxia, and loss of pain and temperature sensation. These features result from involvement of the nucleus ambiguus and inferior cerebellar peduncle. The correct answer is b) Dysphagia, hoarseness, and ataxia.
10) Which artery is commonly affected in brainstem infarction at the pontomedullary junction?
a) Basilar artery
b) Posterior cerebral artery
c) Anterior spinal artery
d) Posterior inferior cerebellar artery
Explanation: The basilar artery supplies the pons and upper medulla at the pontomedullary junction. Infarction here may cause cranial nerve deficits (VI, VII) and contralateral motor weakness. The posterior cerebral artery does not supply this region. Hence, the correct answer is a) Basilar artery.
Chapter: Neuroanatomy; Topic: Cranial Nerves; Subtopic: Trochlear Nerve and its Unique Features
Keyword Definitions:
Cranial nerves: Twelve pairs of nerves that arise directly from the brain and brainstem, responsible for sensory and motor innervation to the head and neck.
Brainstem: The central part of the brain consisting of the midbrain, pons, and medulla oblongata, controlling vital reflexes.
Trochlear nerve (CN IV): The only cranial nerve emerging dorsally from the brainstem and the smallest in size. It supplies the superior oblique muscle of the eye.
Dorsal exit: Refers to a nerve emerging from the posterior (back) aspect of the brainstem.
Superior oblique muscle: Muscle responsible for intorsion and depression of the eyeball, controlled by CN IV.
Lead Question – 2014
Which is the only nerve which exits the brainstem on dorsal side?
a) Facial
b) Trigeminal
c) Trochlear
d) Abducent
Explanation:
The trochlear nerve (CN IV) is unique as it exits from the dorsal aspect of the brainstem, just below the inferior colliculus. It also decussates before emerging, supplying the contralateral superior oblique muscle. This dorsal emergence distinguishes it from all other cranial nerves, which exit ventrally or laterally. Hence, the correct answer is Trochlear (c).
1) The trochlear nerve supplies which muscle?
a) Superior rectus
b) Superior oblique
c) Inferior oblique
d) Lateral rectus
Explanation: The trochlear nerve supplies the superior oblique muscle, responsible for intorsion and depression of the eyeball. It helps move the eye downward and inward. Its lesion leads to vertical diplopia, especially when looking downward, such as reading or descending stairs.
2) Which cranial nerve has the longest intracranial course?
a) Trochlear
b) Abducent
c) Trigeminal
d) Facial
Explanation: The trochlear nerve has the longest intracranial course and is most prone to injury during head trauma. It travels around the midbrain before entering the orbit through the superior orbital fissure. The correct answer is Trochlear (a).
3) Which cranial nerve nucleus lies in the midbrain at the level of the inferior colliculus?
a) Oculomotor
b) Trochlear
c) Abducent
d) Facial
Explanation: The trochlear nucleus lies in the midbrain at the level of the inferior colliculus. The nerve fibers decussate before emerging dorsally. This unique crossing explains contralateral superior oblique muscle innervation. The correct answer is Trochlear (b).
4) A patient presents with vertical diplopia, worsened when looking down. Which nerve is likely affected?
a) Oculomotor
b) Trochlear
c) Abducent
d) Optic
Explanation: Lesion of the trochlear nerve causes vertical diplopia due to paralysis of the superior oblique muscle. The patient tilts the head away from the affected side to compensate. The correct answer is Trochlear (b).
5) Which cranial nerve decussates before emerging from the brainstem?
a) Optic
b) Trochlear
c) Abducent
d) Facial
Explanation: The trochlear nerve is the only cranial nerve to fully cross (decussate) within the brainstem before exiting dorsally. Each nucleus thus controls the contralateral superior oblique muscle. The correct answer is Trochlear (b).
6) During head trauma, which cranial nerve is most likely injured due to its long intracranial course?
a) Oculomotor
b) Trochlear
c) Abducent
d) Facial
Explanation: Because the trochlear nerve travels the longest intracranial path, it is highly susceptible to shearing forces in head injury. Patients experience difficulty looking down, particularly when reading. The correct answer is Trochlear (b).
7) The trochlear nerve exits the brainstem from which structure?
a) Medulla
b) Pons
c) Midbrain
d) Cerebellum
Explanation: The trochlear nerve arises from the dorsal aspect of the midbrain at the level of the inferior colliculus. It then wraps around the brainstem anteriorly to enter the cavernous sinus. The correct answer is Midbrain (c).
8) A patient cannot look down when walking downstairs. Which muscle is weak?
a) Superior rectus
b) Superior oblique
c) Inferior rectus
d) Lateral rectus
Explanation: Weakness of the superior oblique muscle due to trochlear nerve palsy causes inability to look downward when the eye is adducted. This results in vertical diplopia. The correct answer is Superior oblique (b).
9) Which cranial nerve controls the downward gaze of the eyeball?
a) Oculomotor
b) Trochlear
c) Abducent
d) Optic
Explanation: The trochlear nerve controls the superior oblique muscle, which assists in downward gaze, especially when the eye is adducted. Lesion leads to upward deviation and diplopia. The correct answer is Trochlear (b).
10) A patient presents with head tilt to the right and vertical diplopia. Which nerve is likely affected?
a) Right oculomotor
b) Left trochlear
c) Right trochlear
d) Left abducent
Explanation: A lesion of the right trochlear nerve causes the right eye to deviate upward due to superior oblique paralysis. The patient tilts the head to the left to compensate for diplopia. The correct answer is Right trochlear (c).
Chapter: Neuroanatomy; Topic: Cranial Nerve Pathways; Subtopic: Trigeminal Ganglion and Meckel’s Cave
Keyword Definitions:
• Meckel’s Cave: A dural pouch in the middle cranial fossa housing the trigeminal ganglion.
• Trigeminal Ganglion: Sensory ganglion of cranial nerve V located within Meckel’s cave.
• Otic Ganglion: A small parasympathetic ganglion located below the foramen ovale, linked to the glossopharyngeal nerve.
• Pterygopalatine Ganglion: Parasympathetic ganglion in the pterygopalatine fossa associated with facial nerve fibers.
• Submandibular Ganglion: Parasympathetic ganglion associated with chorda tympani and lingual nerve supplying submandibular glands.
Lead Question – 2014
Meckel's cave is related to?
a) Submandibular ganglion
b) Trigeminal ganglion
c) Otic ganglion
d) Pterygopalatine ganglion
Explanation:
Meckel’s cave is a dural recess in the middle cranial fossa that contains the trigeminal ganglion (Gasserian ganglion). It provides cushioning and protection to the ganglion and its divisions. The space is filled with cerebrospinal fluid and communicates with the subarachnoid space. Therefore, the correct answer is trigeminal ganglion.
1. Meckel’s cave is located in which cranial fossa?
a) Anterior
b) Middle
c) Posterior
d) None
2. The trigeminal ganglion lies within:
a) Cavernous sinus
b) Meckel’s cave
c) Foramen ovale
d) Internal auditory meatus
3. Trigeminal ganglion gives rise to how many main divisions?
a) One
b) Two
c) Three
d) Four
4. Which structure passes through the foramen rotundum?
a) Maxillary nerve
b) Mandibular nerve
c) Ophthalmic nerve
d) Facial nerve
5. Which cranial nerve is most likely affected if there is lesion in Meckel’s cave?
a) CN IV
b) CN V
c) CN VI
d) CN VII
6. A patient presents with loss of corneal reflex and facial pain. The lesion most likely involves:
a) Otic ganglion
b) Trigeminal ganglion
c) Geniculate ganglion
d) Pterygopalatine ganglion
7. The dural covering of Meckel’s cave is derived from:
a) Pia mater
b) Arachnoid mater
c) Dura mater
d) Endosteum
8. A tumor compressing Meckel’s cave may lead to which symptom?
a) Anosmia
b) Trigeminal neuralgia
c) Vertigo
d) Diplopia
9. Pterygopalatine ganglion is associated with which cranial nerve?
a) Facial nerve
b) Glossopharyngeal nerve
c) Trigeminal nerve
d) Vagus nerve
10. Otic ganglion is related to which nerve fiber type?
a) Sensory fibers of trigeminal nerve
b) Parasympathetic fibers from glossopharyngeal nerve
c) Sympathetic fibers from carotid plexus
d) Somatic motor fibers
11. During skull base surgery, damage to Meckel’s cave may result in loss of sensation from:
a) Ear and scalp
b) Cornea and face
c) Tongue and palate
d) Jaw and larynx
Explanation:
Meckel’s cave houses the trigeminal ganglion and is an important structure in skull base anatomy. Compression of this space can lead to trigeminal neuralgia, facial pain, or sensory loss in the face. It is located in the middle cranial fossa, posterior to the cavernous sinus, lined by dura mater. Thus, the correct answer is trigeminal ganglion.
Topic: Reflex Arcs; Subtopic: Cremasteric Reflex
Keyword Definitions:
Cremasteric Reflex: A superficial reflex that causes elevation of the testis on stroking the inner thigh.
Genitofemoral Nerve: A mixed nerve from L1–L2 spinal segments, with genital and femoral branches.
Afferent Limb: The sensory pathway carrying impulse to spinal cord.
Efferent Limb: The motor pathway carrying impulse to muscle.
Lead Question - 2014
True about cremasteric reflex?
a) Afferent: genital branch of genitofemoral nerve
b) Efferent: genital branch of genitofemoral nerve
c) Efferent: femoral branch of genitofemoral nerve
d) Afferent: pudendal nerve
Explanation: The cremasteric reflex has an afferent limb through the femoral branch of the genitofemoral nerve and the ilioinguinal nerve, and an efferent limb through the genital branch of the genitofemoral nerve causing contraction of the cremaster muscle. Answer: b) Efferent: genital branch of genitofemoral nerve.
1. Absence of cremasteric reflex indicates lesion at which spinal level?
a) T10–T11
b) L1–L2
c) S1–S2
d) C5–C6
The cremasteric reflex is mediated through L1–L2 spinal segments. Its absence suggests a lesion involving these levels, as in spinal cord injury or testicular torsion. Answer: b) L1–L2.
2. Cremaster muscle is derived from which layer of the abdominal wall?
a) External oblique
b) Internal oblique
c) Transversus abdominis
d) Fascia transversalis
The cremaster muscle is a continuation of the internal oblique muscle fibers and forms part of the spermatic cord. Its contraction elevates the testis. Answer: b) Internal oblique.
3. Which nerve carries the sensory component of the cremasteric reflex?
a) Femoral branch of genitofemoral nerve
b) Genital branch of genitofemoral nerve
c) Pudendal nerve
d) Iliohypogastric nerve
The sensory (afferent) limb of the cremasteric reflex is carried mainly by the femoral branch of the genitofemoral nerve and partially by the ilioinguinal nerve. Answer: a) Femoral branch of genitofemoral nerve.
4. In testicular torsion, cremasteric reflex is:
a) Exaggerated
b) Absent
c) Normal
d) Delayed
In testicular torsion, the cremasteric reflex is typically absent on the affected side due to compromised nerve supply and pain inhibition. This is a key clinical diagnostic feature. Answer: b) Absent.
5. Which muscle contraction is responsible for the cremasteric reflex?
a) Dartos muscle
b) Cremaster muscle
c) External oblique
d) Transversus abdominis
The cremasteric reflex involves contraction of the cremaster muscle, causing elevation of the testis. This muscle is innervated by the genital branch of the genitofemoral nerve. Answer: b) Cremaster muscle.
6. Clinical case: A 25-year-old male presents after trauma to the upper thigh with absent cremasteric reflex. Which nerve is likely injured?
a) Ilioinguinal nerve
b) Genitofemoral nerve
c) Pudendal nerve
d) Obturator nerve
Damage to the genitofemoral nerve disrupts both the afferent and efferent limbs of the cremasteric reflex, leading to its absence. Answer: b) Genitofemoral nerve.
7. A newborn has undescended testes and absent cremasteric reflex. What is the most likely cause?
a) Cryptorchidism
b) Hydrocele
c) Hernia
d) Varicocele
In cryptorchidism, the testis fails to descend into the scrotum, leading to absent cremasteric reflex due to abnormal nerve and muscle development. Answer: a) Cryptorchidism.
8. Afferent fibers of cremasteric reflex travel through:
a) Femoral branch of genitofemoral nerve
b) Ilioinguinal nerve
c) Both a and b
d) None
Both the femoral branch of the genitofemoral nerve and ilioinguinal nerve contribute sensory input from the inner thigh to the spinal cord. Answer: c) Both a and b.
9. Which reflex is mediated at the spinal level S1–S2?
a) Cremasteric reflex
b) Anal reflex
c) Abdominal reflex
d) Plantar reflex
The anal reflex, not the cremasteric reflex, is mediated at the S1–S2 level. The cremasteric reflex is L1–L2. Answer: b) Anal reflex.
10. Clinical case: A man with spinal cord injury above L1–L2 shows absent cremasteric reflex but intact anal reflex. Which statement is correct?
a) Reflex arc of cremasteric is intact
b) Reflex arc of cremasteric is interrupted
c) Pudendal nerve involved
d) Reflex mediated by S2–S4
The cremasteric reflex arc is interrupted in lesions above L1–L2, abolishing the reflex, while the anal reflex (S2–S4) remains intact. Answer: b) Reflex arc of cremasteric is interrupted.
Subtopic: Nerves of Thorax – Vagus and Phrenic Nerves
Keyword Definitions:
Vagus nerve: The tenth cranial nerve supplying parasympathetic fibers to thoracic and abdominal viscera.
Phrenic nerve: Arises from C3–C5 spinal roots, providing motor supply to the diaphragm.
Arch of aorta: The curved portion of the aorta giving rise to major arteries of the upper body.
Thoracic cavity: The chest space containing lungs, heart, and major vessels.
Lead Question (2014):
At the level of Arch of aorta, the relationship of left vagus nerve and left phrenic nerve?
a) Phrenic nerve anterior, vagus nerve posterior
b) Phrenic nerve posterior, vagus nerve anterior
c) Both in same plane anteroposteriorly
d) Variable in relationship
Explanation:
At the level of the aortic arch, the left phrenic nerve lies anterior to the left vagus nerve. Answer: a) Phrenic nerve anterior, vagus nerve posterior. The vagus nerve gives off the left recurrent laryngeal branch here, looping under the arch near the ligamentum arteriosum.
1)
The left recurrent laryngeal nerve hooks around which structure in the thorax?
a) Right subclavian artery
b) Arch of aorta
c) Pulmonary trunk
d) Left subclavian vein
The left recurrent laryngeal nerve hooks under the arch of the aorta, close to the ligamentum arteriosum. Answer: b) Arch of aorta. This explains why enlargement of mediastinal nodes or aneurysm can cause hoarseness due to recurrent laryngeal nerve compression.
2)
Which of the following nerves carries parasympathetic fibers to the thoracic and abdominal organs?
a) Phrenic nerve
b) Vagus nerve
c) Intercostal nerve
d) Sympathetic trunk
The vagus nerve provides parasympathetic supply to most thoracic and abdominal viscera. Answer: b) Vagus nerve. It slows heart rate, enhances gastrointestinal motility, and modulates glandular secretions through its autonomic fibers descending through the thorax into the abdomen.
3)
A 60-year-old man with hoarseness of voice is found to have an aortic aneurysm. Which nerve is most likely compressed?
a) Right phrenic
b) Left phrenic
c) Left recurrent laryngeal
d) Right vagus
An aortic arch aneurysm can compress the left recurrent laryngeal nerve as it loops beneath the arch. Answer: c) Left recurrent laryngeal. This causes hoarseness due to paralysis of the left vocal cord supplied by this branch of the vagus nerve.
4)
Phrenic nerve arises from which spinal segments?
a) C1–C3
b) C2–C4
c) C3–C5
d) C4–C6
The phrenic nerve originates mainly from cervical spinal nerves C3, C4, and C5. Answer: c) C3–C5. Its mnemonic “C3, 4, and 5 keep the diaphragm alive” emphasizes its importance in diaphragmatic contraction and maintenance of respiratory function.
5)
In thoracic surgery, which nerve must be carefully preserved to avoid diaphragmatic paralysis?
a) Vagus
b) Intercostal
c) Phrenic
d) Recurrent laryngeal
The phrenic nerve supplies the diaphragm motor fibers. Injury during surgery may cause hemidiaphragm paralysis and breathing difficulty. Answer: c) Phrenic. Its anterior location on the pericardium makes it vulnerable in cardiac or mediastinal procedures.
6)
The right vagus nerve passes posterior to which thoracic structure?
a) Right pulmonary root
b) Left pulmonary root
c) Arch of aorta
d) Pulmonary trunk
The right vagus nerve passes posterior to the right pulmonary root, whereas the left vagus lies anterior to the left root. Answer: a) Right pulmonary root. These relations are clinically important during lung and mediastinal surgeries to avoid nerve injury.
7)
A trauma patient presents with left hemidiaphragmatic paralysis. Which nerve is most likely injured?
a) Left vagus
b) Left phrenic
c) Right vagus
d) Left intercostal
Diaphragmatic paralysis on one side indicates phrenic nerve damage. Answer: b) Left phrenic. The phrenic nerve runs along the pericardium and can be injured by penetrating trauma or mediastinal compression, leading to elevation of the hemidiaphragm on chest X-ray.
8)
Which branch of the vagus nerve contributes to the cardiac plexus?
a) Superior cardiac branch
b) Recurrent laryngeal branch
c) Cervical cardiac branch
d) Pulmonary branch
The cervical cardiac branches of the vagus nerve descend to form part of the cardiac plexus, supplying parasympathetic fibers to the heart. Answer: c) Cervical cardiac branch. These fibers help decrease heart rate and modulate conduction through the atrioventricular node.
9)
A mediastinal tumor compressing the left phrenic nerve would cause which symptom?
a) Hoarseness
b) Dysphagia
c) Dyspnea on exertion
d) Loss of cough reflex
Compression of the left phrenic nerve results in paralysis of the left diaphragm, producing breathlessness on exertion. Answer: c) Dyspnea on exertion. This occurs because the affected hemidiaphragm fails to contract effectively, reducing lung expansion during inspiration.
10)
The vagus nerve forms which plexus on the esophagus before entering the abdomen?
a) Pulmonary plexus
b) Cardiac plexus
c) Esophageal plexus
d) Gastric plexus
Before passing through the diaphragm, the vagus nerve forms the esophageal plexus around the esophagus. Answer: c) Esophageal plexus. These fibers then reorganize into anterior and posterior vagal trunks that continue into the abdomen to supply visceral organs.
Topic: Lumbar Plexus
Subtopic: Nerve Branches
Keyword Definitions:
Lumbar plexus: A network of nerves in the posterior abdominal wall formed by ventral rami of L1–L4 spinal nerves.
Iliohypogastric nerve: Branch of lumbar plexus supplying abdominal wall and skin above pubis.
Ilioinguinal nerve: Branch of lumbar plexus supplying groin and upper medial thigh skin.
Obturator nerve: Nerve from lumbar plexus supplying medial thigh muscles.
Subcostal nerve: A branch of T12 nerve, not part of the lumbar plexus.
Lead Question - 2014
All are branches of lumbar plexus except?
a) Iliohypogastric nerve
b) Ilioinguinal nerve
c) Obturator nerve
d) Subcostal nerve
Explanation: The lumbar plexus arises from L1–L4 spinal nerves. It gives branches such as iliohypogastric, ilioinguinal, genitofemoral, femoral, and obturator nerves. The subcostal nerve is from T12 and not part of the lumbar plexus. Hence, the correct answer is d) Subcostal nerve.
1. The lumbar plexus is formed by which spinal segments?
a) L1–L3
b) L1–L4
c) L2–L5
d) T12–L3
Explanation: The lumbar plexus is formed by ventral rami of L1–L4, with a contribution from T12 in some cases. It supplies abdominal wall, thigh, and pelvic regions. Correct answer: b) L1–L4.
2. Which nerve of the lumbar plexus supplies the skin of the lateral thigh?
a) Genitofemoral
b) Lateral femoral cutaneous
c) Ilioinguinal
d) Obturator
Explanation: The lateral femoral cutaneous nerve, a branch of the lumbar plexus (L2–L3), supplies sensation to the lateral thigh. Lesion causes meralgia paresthetica. Correct answer: b) Lateral femoral cutaneous.
3. A patient presents with difficulty adducting the thigh. Which nerve is affected?
a) Obturator nerve
b) Femoral nerve
c) Sciatic nerve
d) Iliohypogastric nerve
Explanation: The obturator nerve supplies adductor muscles of the medial thigh. Injury leads to loss of thigh adduction and sensory loss in medial thigh. Correct answer: a) Obturator nerve.
4. The femoral nerve arises from which roots?
a) L2–L4
b) L1–L3
c) L3–L5
d) T12–L2
Explanation: The femoral nerve is the largest branch of the lumbar plexus and arises from L2–L4 roots. It supplies anterior thigh muscles and skin over anterior thigh and medial leg. Correct answer: a) L2–L4.
5. During hernia repair, which nerve is most at risk of injury in the inguinal canal?
a) Femoral
b) Ilioinguinal
c) Obturator
d) Genitofemoral
Explanation: The ilioinguinal nerve passes through the inguinal canal and is commonly at risk during hernia surgeries. Its injury causes numbness over groin and upper medial thigh. Correct answer: b) Ilioinguinal.
6. Which lumbar plexus nerve supplies the cremaster muscle in males?
a) Ilioinguinal
b) Genitofemoral
c) Obturator
d) Femoral
Explanation: The genital branch of the genitofemoral nerve supplies the cremaster muscle and scrotal skin in males. It is tested by the cremasteric reflex. Correct answer: b) Genitofemoral.
7. A patient has anesthesia over the anterior thigh and medial leg. Which nerve is most likely damaged?
a) Obturator
b) Femoral
c) Ilioinguinal
d) Genitofemoral
Explanation: The femoral nerve supplies sensation to the anterior thigh and via the saphenous branch to medial leg. Damage results in anesthesia and weakness of knee extension. Correct answer: b) Femoral nerve.
8. Which nerve is NOT a branch of the lumbar plexus?
a) Genitofemoral
b) Pudendal
c) Iliohypogastric
d) Lateral femoral cutaneous
Explanation: The pudendal nerve arises from the sacral plexus (S2–S4) and is not a branch of the lumbar plexus. Correct answer: b) Pudendal.
9. A patient develops burning pain over the lateral thigh after tight clothing. Which nerve is compressed?
a) Obturator
b) Lateral femoral cutaneous
c) Genitofemoral
d) Femoral
Explanation: Compression of the lateral femoral cutaneous nerve (L2–L3) causes meralgia paresthetica, presenting with burning pain and numbness over lateral thigh. Correct answer: b) Lateral femoral cutaneous.
10. Which of the following supplies the quadriceps femoris muscle?
a) Femoral nerve
b) Obturator nerve
c) Lateral femoral cutaneous
d) Genitofemoral
Explanation: The quadriceps femoris is the chief extensor of the knee, innervated by the femoral nerve (L2–L4). Correct answer: a) Femoral nerve.
11. A pelvic fracture injures the obturator nerve. Which action is lost?
a) Hip flexion
b) Hip extension
c) Hip adduction
d) Knee extension
Explanation: The obturator nerve supplies adductor muscles. Injury results in loss of thigh adduction with sensory deficit over medial thigh. Correct answer: c) Hip adduction.
Topic: Nerve Supply of Foot Muscles
Subtopic: Lumbricals of Foot
Keyword Definitions:
Lumbricals (foot): Four small intrinsic muscles of the foot, flex metatarsophalangeal joints and extend interphalangeal joints.
Medial plantar nerve: Branch of tibial nerve, supplies abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, and 1st lumbrical.
Lateral plantar nerve: Branch of tibial nerve, supplies most intrinsic muscles of the foot including 2nd–4th lumbricals.
Tibial nerve: Main posterior leg nerve, parent of medial and lateral plantar nerves.
Peroneal nerve: Supplies anterior and lateral compartments of leg, not lumbricals.
Lead Question - 2014
3rd and 4th lumbrical (lateral two lumbricals) of foot are supplied by?
a) Medial plantar nerve
b) Lateral plantar nerve
c) Peroneal nerve
d) None of the above
Explanation: The 1st lumbrical of the foot is supplied by the medial plantar nerve. The 2nd, 3rd, and 4th lumbricals are supplied by the lateral plantar nerve. Thus, the 3rd and 4th lumbricals specifically receive innervation from the lateral plantar nerve. Correct answer: Lateral plantar nerve.
1) Which lumbrical of the foot is supplied by medial plantar nerve?
a) 1st
b) 2nd
c) 3rd
d) 4th
Explanation: Only the first lumbrical of the foot is supplied by the medial plantar nerve. The remaining lumbricals (2nd to 4th) are supplied by the lateral plantar nerve. Correct answer is 1st.
2) A patient presents with weakness in toe flexion at metatarsophalangeal joints. Which muscles are primarily involved?
a) Lumbricals
b) Interossei
c) Extensors
d) Plantar aponeurosis
Explanation: Lumbricals flex the metatarsophalangeal joints and extend the interphalangeal joints. Weakness in these movements is indicative of lumbrical muscle dysfunction. Correct answer is Lumbricals.
3) Which nerve injury leads to loss of function of lateral three lumbricals of foot?
a) Medial plantar nerve
b) Lateral plantar nerve
c) Deep peroneal nerve
d) Superficial peroneal nerve
Explanation: The lateral plantar nerve supplies the 2nd, 3rd, and 4th lumbricals. Injury to this nerve results in loss of function of the lateral three lumbricals. Correct answer is Lateral plantar nerve.
4) Which compartment of foot contains lumbricals?
a) Medial
b) Lateral
c) Central
d) Interosseous
Explanation: The lumbricals are located in the central compartment of the foot, along with flexor digitorum brevis and tendons of flexor digitorum longus. Correct answer is Central.
5) Lumbricals of the foot act on which joints?
a) Only ankle
b) Only knee
c) Metatarsophalangeal and interphalangeal joints
d) Tarsal joints
Explanation: Lumbricals flex the metatarsophalangeal joints and extend interphalangeal joints, thus balancing flexors and extensors during walking. Correct answer is Metatarsophalangeal and interphalangeal joints.
6) A football player has tibial nerve injury at ankle. Which lumbrical remains functional?
a) 1st
b) 2nd
c) 3rd
d) None
Explanation: Both medial and lateral plantar nerves are branches of tibial nerve. Injury at ankle compromises all lumbricals. Hence, no lumbrical remains functional. Correct answer is None.
7) Which intrinsic foot muscles are supplied by medial plantar nerve along with 1st lumbrical?
a) Flexor hallucis brevis, abductor hallucis, flexor digitorum brevis
b) Interossei
c) Adductor hallucis
d) Lateral two lumbricals
Explanation: Medial plantar nerve supplies abductor hallucis, flexor hallucis brevis, flexor digitorum brevis, and 1st lumbrical. The rest are supplied by the lateral plantar nerve. Correct answer is Flexor hallucis brevis, abductor hallucis, flexor digitorum brevis.
8) In clawing of toes due to lumbrical paralysis, what happens?
a) Hyperextension of MTP, flexion of IP
b) Flexion of MTP, extension of IP
c) Both extended
d) Both flexed
Explanation: Lumbricals normally flex the MTP joints and extend the IP joints. Paralysis leads to opposite deformity: hyperextension at MTP and flexion at IP joints, causing claw toe deformity. Correct answer is Hyperextension of MTP, flexion of IP.
9) Which tendon gives origin to lumbricals of foot?
a) Flexor digitorum longus
b) Flexor digitorum brevis
c) Extensor digitorum longus
d) Extensor digitorum brevis
Explanation: All four lumbricals of the foot arise from tendons of flexor digitorum longus. Correct answer is Flexor digitorum longus.
10) A patient with lateral plantar nerve injury is most likely to lose which movement?
a) Flexion of great toe
b) Extension of toes
c) Flexion at MTP and extension at IP of lateral toes
d) Inversion of foot
Explanation: Lateral plantar nerve supplies lateral three lumbricals. Their paralysis causes inability to flex MTP and extend IP joints of lateral toes. Correct answer is Flexion at MTP and extension at IP of lateral toes.
Topic: Upper Limb
Subtopic: Brachial Artery and Radial Nerve Relations
Keyword Definitions:
Profunda brachii artery: Deep branch of brachial artery, runs in the spiral groove of humerus, supplies posterior compartment of arm.
Spiral groove: Groove on posterior aspect of humerus where radial nerve and profunda brachii artery travel together.
Radial nerve: Nerve of posterior compartment of arm, supplies triceps and forearm extensors, runs with profunda brachii artery in spiral groove.
Ulnar nerve: Runs medial arm, behind medial epicondyle, unrelated to profunda brachii artery.
Median nerve: Runs with brachial artery in anterior compartment of arm.
Lead Question - 2014
Nerve running along with profunda brachii artery, in spiral groove?
a) Ulnar
b) Median
c) Radial
d) None
Explanation: The radial nerve runs in the spiral groove of humerus alongside the profunda brachii artery, supplying the posterior compartment of the arm. Injury here can lead to wrist drop. Correct answer is Radial.
Guessed Questions
1. Nerve vulnerable in mid-shaft humerus fracture?
a) Median
b) Radial
c) Ulnar
d) Musculocutaneous
Explanation: Mid-shaft humerus fractures can injure the radial nerve as it lies in the spiral groove along with the profunda brachii artery. This can cause wrist drop and sensory deficits over dorsum of hand. Correct answer is Radial.
2. Profunda brachii artery is a branch of?
a) Axillary artery
b) Brachial artery
c) Subclavian artery
d) Radial artery
Explanation: The profunda brachii artery is the deep branch of the brachial artery, running in the posterior compartment of arm alongside the radial nerve in the spiral groove. Correct answer is Brachial artery.
3. Muscle supplied by nerve in spiral groove?
a) Biceps brachii
b) Triceps brachii
c) Brachialis
d) Pronator teres
Explanation: The radial nerve running in the spiral groove supplies the triceps brachii muscle of posterior compartment. Injury at this site affects elbow extension. Correct answer is Triceps brachii.
4. Sensory area of radial nerve in arm?
a) Medial forearm
b) Dorsum of lateral hand
c) Palm of hand
d) Posterior arm only
Explanation: The radial nerve provides sensory innervation to the dorsum of lateral hand and posterior arm/forearm. Mid-shaft injury in spiral groove can cause sensory deficits here. Correct answer is Dorsum of lateral hand.
5. Complication of radial nerve injury in spiral groove?
a) Claw hand
b) Wrist drop
c) Foot drop
d) Ape hand
Explanation: Injury to the radial nerve in the spiral groove leads to wrist drop due to paralysis of wrist extensors, while elbow extension may be preserved. Correct answer is Wrist drop.
6. Spiral groove is located on?
a) Anterior humerus
b) Posterior humerus
c) Medial epicondyle
d) Lateral epicondyle
Explanation: The spiral groove is a groove on the posterior aspect of the humerus where the radial nerve and profunda brachii artery travel together. Correct answer is Posterior humerus.
7. Nerve supplying forearm extensors?
a) Median
b) Radial
c) Ulnar
d) Musculocutaneous
Explanation: The radial nerve, after running in spiral groove with profunda brachii artery, continues to innervate forearm extensors. Injury leads to weakness in wrist and finger extension. Correct answer is Radial.
8. Profunda brachii artery enters posterior compartment via?
a) Triangular interval
b) Quadrangular space
c) Cubital fossa
d) Medial intermuscular septum
Explanation: The profunda brachii artery enters the posterior compartment of arm through the triangular interval, running with the radial nerve in spiral groove. Correct answer is Triangular interval.
9. Clinical test for radial nerve injury?
a) Elbow flexion test
b) Wrist extension test
c) Thumb opposition test
d) Finger abduction test
Explanation: The wrist extension test assesses function of the radial nerve. Injury in spiral groove causes wrist drop, inability to extend wrist. Correct answer is Wrist extension test.
10. Surgical landmark for profunda brachii artery?
a) Lateral epicondyle
b) Spiral groove of humerus
c) Medial epicondyle
d) Olecranon
Explanation: The spiral groove of humerus is the surgical landmark where the profunda brachii artery runs with radial nerve. Knowledge helps prevent iatrogenic injury. Correct answer is Spiral groove of humerus.
Topic: Upper Limb
Subtopic: Cubital Fossa Structures
Keyword Definitions:
Bicipital aponeurosis: A broad fibrous expansion from biceps brachii tendon crossing cubital fossa, protecting underlying structures.
Cubital fossa: Triangular area anterior to elbow joint, containing important nerves and vessels.
Brachial artery: Main artery of upper arm continuing from axillary artery to cubital fossa.
Ulnar nerve: Nerve passing medial to cubital fossa, supplying intrinsic hand muscles.
Anterior interosseous artery: Branch of ulnar artery running along forearm interosseous membrane.
Lead Question - 2014
Bicipital aponeurosis lies over which structure in cubital fossa?
a) Ulnar nerve
b) Radial nerve
c) Brachial artery
d) Anterior interosseous artery
Explanation: The bicipital aponeurosis is a fibrous expansion from the biceps tendon that lies superficial to the brachial artery in the cubital fossa, providing protection to this major vessel during venipuncture or trauma. Correct answer is Brachial artery.
Guessed Questions
1. Ulnar nerve lies medial to which structure in cubital fossa?
a) Brachial artery
b) Bicipital aponeurosis
c) Median nerve
d) Radial artery
Explanation: The ulnar nerve passes medial to the cubital fossa, lying behind the medial epicondyle and not under the bicipital aponeurosis. Correct answer is Brachial artery lies anterior to it, but ulnar nerve is medial to cubital fossa structures.
2. Median nerve in cubital fossa is located?
a) Lateral to brachial artery
b) Medial to brachial artery
c) Superficial to bicipital aponeurosis
d) Posterior to brachial artery
Explanation: The median nerve lies medial to the brachial artery in cubital fossa and deep to the bicipital aponeurosis, ensuring protection during venipuncture. Correct answer is Medial to brachial artery.
3. Bicipital aponeurosis prevents injury to?
a) Radial nerve
b) Brachial artery
c) Ulnar artery
d) Median cubital vein
Explanation: The bicipital aponeurosis covers the brachial artery and median nerve in cubital fossa, protecting them from superficial lacerations during venipuncture or trauma. Correct answer is Brachial artery.
4. Cephalic vein in cubital fossa lies relative to bicipital aponeurosis?
a) Superficial
b) Deep
c) Lateral
d) Medial
Explanation: The cephalic vein lies superficial to the bicipital aponeurosis in the cubital fossa, allowing easy access for venipuncture without injuring deeper structures. Correct answer is Superficial.
5. Anterior interosseous artery is branch of?
a) Radial artery
b) Brachial artery
c) Ulnar artery
d) Median artery
Explanation: The anterior interosseous artery arises from the ulnar artery, passes along the interosseous membrane supplying deep flexor muscles of forearm. It is not covered by bicipital aponeurosis. Correct answer is Ulnar artery.
6. Structures passing deep to bicipital aponeurosis?
a) Median cubital vein
b) Brachial artery
c) Cephalic vein
d) Superficial radial nerve
Explanation: Brachial artery and median nerve lie deep to the bicipital aponeurosis in cubital fossa, providing protection from superficial trauma. Superficial veins lie above the aponeurosis. Correct answer is Brachial artery.
7. Radial nerve in cubital fossa lies?
a) Medial to biceps tendon
b) Lateral and deep to brachioradialis
c) Superficial to brachialis
d) Under bicipital aponeurosis
Explanation: The radial nerve passes laterally, deep to brachioradialis, and does not lie under the bicipital aponeurosis. Correct answer is Lateral and deep to brachioradialis.
8. Median cubital vein is located?
a) Superficial to bicipital aponeurosis
b) Deep to bicipital aponeurosis
c) Deep to brachial artery
d) Between brachial artery and ulnar nerve
Explanation: Median cubital vein is superficial to the bicipital aponeurosis, connecting cephalic and basilic veins in cubital fossa, commonly used for venipuncture. Correct answer is Superficial to bicipital aponeurosis.
9. Clinical importance of bicipital aponeurosis?
a) Protects brachial artery
b) Guides venipuncture
c) Can be injured in lacerations
d) All of the above
Explanation: The bicipital aponeurosis protects brachial artery and median nerve, provides a landmark for venipuncture, and may be injured in trauma. Correct answer is All of the above.
10. Injury under bicipital aponeurosis may affect?
a) Radial nerve
b) Median nerve
c) Cephalic vein
d) Basilic vein
Explanation: Structures deep to bicipital aponeurosis include brachial artery and median nerve. Injury here can cause hemorrhage and loss of hand function. Radial nerve lies laterally and cephalic vein superficially. Correct answer is Median nerve.
Topic: Upper Limb
Subtopic: Hand Muscles Innervation
Keyword Definitions:
Small muscles of hand: Intrinsic hand muscles including thenar, hypothenar, lumbricals, and interossei, responsible for fine motor movements.
Innervation: Nerve supply to muscles, determining motor function.
C5-T1 roots: Spinal nerve roots forming the brachial plexus supplying upper limb muscles.
Median nerve: Nerve supplying thenar muscles and lateral two lumbricals.
Ulnar nerve: Nerve supplying hypothenar muscles, interossei, and medial two lumbricals.
Lead Question - 2014
Small muscles of hand are supplied by:
a) C3
b) C4
c) C6
d) C5-C7 , C8-T1
Explanation: The small intrinsic muscles of the hand are supplied by nerves originating from C5-C7 (median nerve) and C8-T1 (ulnar nerve). These roots form the brachial plexus, allowing fine motor control. Correct answer is C5-C7 , C8-T1.
Guessed Questions
1. Thenar muscles are supplied by?
a) Ulnar nerve
b) Median nerve
c) Radial nerve
d) Musculocutaneous nerve
Explanation: Thenar muscles controlling thumb movements are innervated by the median nerve, derived from C5-C7 roots of the brachial plexus. Ulnar nerve does not supply thenar muscles except adductor pollicis. Correct answer is Median nerve.
2. Hypothenar muscles are supplied by?
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Axillary nerve
Explanation: Hypothenar muscles (flexor digiti minimi, abductor digiti minimi, opponens digiti minimi) controlling little finger movements are supplied by the ulnar nerve arising from C8-T1 roots. Correct answer is Ulnar nerve.
3. Lumbrical muscles innervation?
a) Median for all
b) Ulnar for all
c) Median for lateral two, Ulnar for medial two
d) Radial nerve
Explanation: Lumbricals 1 and 2 (lateral) are supplied by median nerve, lumbricals 3 and 4 (medial) by ulnar nerve. This allows coordinated finger flexion at MCP joints and extension at IP joints. Correct answer is Median for lateral two, Ulnar for medial two.
4. Interossei muscles are supplied by?
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Axillary nerve
Explanation: Dorsal and palmar interossei of the hand, responsible for finger abduction and adduction, are supplied by ulnar nerve (C8-T1). Median nerve does not supply interossei. Correct answer is Ulnar nerve.
5. Injury to C8-T1 roots affects?
a) Shoulder abduction
b) Elbow flexion
c) Intrinsic hand muscles
d) Wrist extension
Explanation: C8-T1 nerve roots supply the intrinsic hand muscles via ulnar and median nerves. Damage results in weakness of fine motor control, claw hand deformity. Shoulder and elbow muscles are supplied by higher roots. Correct answer is Intrinsic hand muscles.
6. Claw hand is due to injury of?
a) Median nerve
b) Ulnar nerve
c) Both median and ulnar nerves
d) Radial nerve
Explanation: Claw hand deformity occurs when ulnar nerve is injured, leading to hyperextension at MCP and flexion at IP joints. Combined median and ulnar nerve lesions worsen intrinsic hand function. Correct answer is Both median and ulnar nerves.
7. Ape hand deformity is due to?
a) Median nerve injury
b) Ulnar nerve injury
c) Radial nerve injury
d) Axillary nerve injury
Explanation: Ape hand results from median nerve injury, causing loss of thumb opposition, atrophy of thenar muscles, and flattening of thenar eminence. Correct answer is Median nerve injury.
8. Median nerve arises from which roots?
a) C5-C6
b) C5-C7
c) C8-T1
d) C7-T1
Explanation: Median nerve originates from the brachial plexus, receiving contributions from C5-C7 (lateral cord) and C8-T1 (medial cord). Supplies most thenar muscles and lateral lumbricals. Correct answer is C5-C7.
9. Ulnar nerve arises from?
a) Lateral cord
b) Medial cord
c) Posterior cord
d) Musculocutaneous nerve
Explanation: Ulnar nerve arises from medial cord of brachial plexus (C8-T1), supplying hypothenar muscles, medial lumbricals, and interossei. Correct answer is Medial cord.
10. Fine motor control of hand depends on?
a) Only extrinsic muscles
b) Only intrinsic muscles
c) Intrinsic and extrinsic muscles
d) Only wrist muscles
Explanation: Fine hand movements require coordinated action of intrinsic muscles (thenar, hypothenar, interossei, lumbricals) and extrinsic muscles (flexors/extensors of forearm). Both median and ulnar nerves contribute. Correct answer is Intrinsic and extrinsic muscles.
Topic: Reflexes
Subtopic: Supinator (Brachioradialis) Reflex
Keyword Definitions:
Supinator jerk: Also called brachioradialis reflex, elicited by tapping brachioradialis tendon, leading to forearm flexion and supination.
Reflex arc: Neural pathway that mediates a reflex action, involving sensory input, spinal cord integration, and motor output.
C5, C6 roots: Cervical spinal nerve roots contributing to supinator (brachioradialis) reflex.
Neurological examination: Assessment of reflexes helps localize lesions in spinal cord or peripheral nerves.
Clinical relevance: Supinator jerk tests integrity of C5-C6 nerve roots and musculocutaneous/ radial nerves.
Lead Question - 2014
Root value of supinator jerk?
a) C3-C4
b) C4-C5
c) C5-C6
d) C8-T1
Explanation: The supinator (brachioradialis) jerk involves tapping the tendon of brachioradialis, causing flexion and supination of the forearm. This reflex is mediated by the C5-C6 spinal nerve roots. Correct answer is C5-C6.
Guessed Questions
1. Biceps jerk tests which nerve roots?
a) C5-C6
b) C6-C7
c) C7-C8
d) C8-T1
Explanation: The biceps jerk is elicited by tapping the biceps tendon, causing forearm flexion. It tests integrity of C5-C6 nerve roots and musculocutaneous nerve. Correct answer is C5-C6.
2. Triceps jerk assesses?
a) C5-C6
b) C6-C7
c) C7-C8
d) C8-T1
Explanation: The triceps reflex is elicited by tapping the triceps tendon, causing elbow extension. It tests C7-C8 roots and radial nerve function. Correct answer is C7-C8.
3. Supinator jerk is mediated by which nerve?
a) Median nerve
b) Musculocutaneous nerve
c) Radial nerve
d) Ulnar nerve
Explanation: The supinator jerk reflex involves contraction of brachioradialis, mediated by the radial nerve, with sensory input from C5-C6 roots. Correct answer is Radial nerve.
4. Forearm supination in supinator reflex tests integrity of?
a) Muscles only
b) Spinal cord only
c) C5-C6 roots and radial nerve
d) Peripheral nerves only
Explanation: Supinator jerk causes forearm supination, testing C5-C6 nerve roots and radial nerve. Both peripheral nerve and spinal roots must be intact. Correct answer is C5-C6 roots and radial nerve.
5. Absence of supinator jerk suggests?
a) Normal reflex
b) Upper motor neuron lesion
c) Lower motor neuron lesion at C5-C6
d) Cerebellar lesion
Explanation: Absence or diminution of supinator jerk indicates lower motor neuron lesion affecting C5-C6 nerve roots or radial nerve. Upper motor neuron lesions usually cause hyperreflexia. Correct answer is Lower motor neuron lesion at C5-C6.
6. Reinforcement technique for supinator reflex?
a) Jendrassik maneuver
b) Deep breath
c) Leg crossing
d) Valsalva maneuver
Explanation: Jendrassik maneuver (clenching teeth or interlocking fingers) enhances supinator reflex by increasing central excitability. Correct answer is Jendrassik maneuver.
7. Supinator reflex is classified as?
a) Superficial reflex
b) Deep tendon reflex
c) Pathological reflex
d) Cranial reflex
Explanation: The supinator jerk is a deep tendon reflex, elicited by tapping the tendon, involving monosynaptic reflex arc and testing spinal nerve root integrity. Correct answer is Deep tendon reflex.
8. Clinical significance of exaggerated supinator jerk?
a) LMN lesion
b) UMN lesion
c) Peripheral neuropathy
d) Muscle rupture
Explanation: Exaggerated or hyperactive supinator jerk indicates upper motor neuron lesion above C5-C6 level, causing hyperreflexia. Correct answer is UMN lesion.
9. Supinator reflex primarily tests which muscle?
a) Biceps brachii
b) Brachioradialis
c) Triceps brachii
d) Supinator muscle
Explanation: Supinator jerk is elicited by tapping the tendon of brachioradialis, causing forearm flexion and supination. Though supinator muscle participates in supination, the primary muscle tested is brachioradialis. Correct answer is Brachioradialis.
10. Supinator jerk is decreased in which condition?
a) Cervical radiculopathy C5-C6
b) Carpal tunnel syndrome
c) Cubital tunnel syndrome
d) Rotator cuff tear
Explanation: Supinator reflex is reduced or absent in cervical radiculopathy involving C5-C6 because the nerve roots and radial nerve contribution are impaired. Peripheral neuropathies in distal nerves do not affect this reflex. Correct answer is Cervical radiculopathy C5-C6.
Topic: Pectoral Region
Subtopic: Clavipectoral Fascia
Keyword Definitions:
Clavipectoral fascia: Deep fascia beneath pectoralis major, enclosing subclavius and pectoralis minor, extending from clavicle to axilla.
Lateral pectoral nerve: Nerve supplying pectoralis major, passes through clavipectoral fascia.
Median pectoral nerve: Nerve supplying pectoralis minor and part of major, pierces fascia near axilla.
Thoracoacromial vessels: Artery and vein branching from axillary vessels, pierce fascia near pectoralis minor.
Cephalic vein: Superficial vein of upper limb, runs in deltopectoral groove but does not pierce fascia.
Lead Question - 2014
Clavipectoral fascia is pierced by all except?
a) Lateral pectoral nerve
b) Median pectoral nerve
c) Thoracoacromial vessels
d) Cephalic vein
Explanation: The clavipectoral fascia is pierced by the lateral pectoral nerve, median pectoral nerve, and thoracoacromial vessels. However, the cephalic vein runs superficial in the deltopectoral groove and does not pierce the fascia. Therefore, the correct answer is Cephalic vein.
Guessed Questions
1. Lateral pectoral nerve primarily supplies?
a) Pectoralis minor
b) Pectoralis major
c) Subclavius
d) Serratus anterior
Explanation: The lateral pectoral nerve mainly supplies the pectoralis major muscle, especially its clavicular part. It passes through the clavipectoral fascia near pectoralis minor but does not innervate minor or other muscles. Correct answer is Pectoralis major.
2. Median pectoral nerve supplies?
a) Pectoralis major only
b) Pectoralis minor only
c) Pectoralis minor and part of major
d) Deltoid
Explanation: The median pectoral nerve pierces the clavipectoral fascia to supply pectoralis minor and the lower fibers of pectoralis major. It does not supply deltoid. Correct answer is Pectoralis minor and part of major.
3. Thoracoacromial artery branches into all except?
a) Pectoral branch
b) Acromial branch
c) Clavicular branch
d) Lateral thoracic branch
Explanation: The thoracoacromial artery pierces the clavipectoral fascia and branches into pectoral, acromial, clavicular, and deltoid branches. Lateral thoracic artery is separate from axillary artery. Correct answer is Lateral thoracic branch.
4. Cephalic vein drains into?
a) Axillary vein
b) Subclavian vein
c) Basilic vein
d) Brachial vein
Explanation: The superficial cephalic vein runs in deltopectoral groove and drains into the axillary vein near clavipectoral fascia. It does not pierce the fascia. Correct answer is Axillary vein.
5. Clavipectoral fascia encloses which muscles?
a) Pectoralis major
b) Pectoralis minor and subclavius
c) Deltoid
d) Serratus anterior
Explanation: The clavipectoral fascia lies deep to pectoralis major and encloses pectoralis minor and subclavius muscles. It does not enclose deltoid or serratus anterior. Correct answer is Pectoralis minor and subclavius.
6. Deltopectoral triangle is bounded by?
a) Clavicle, deltoid, pectoralis major
b) Scapula, deltoid, trapezius
c) Clavicle, trapezius, pectoralis minor
d) Deltoid, biceps, coracoid
Explanation: The deltopectoral triangle is formed by clavicle superiorly, deltoid laterally, and pectoralis major medially. It contains the cephalic vein and deltopectoral lymph nodes. Correct answer is Clavicle, deltoid, pectoralis major.
7. Clavipectoral fascia attaches inferiorly to?
a) First rib
b) Sternum
c) Axillary fascia
d) Coracoid process
Explanation: The clavipectoral fascia descends from clavicle and attaches inferiorly to the axillary fascia and encases subclavius and pectoralis minor. Correct answer is Axillary fascia.
8. Lateral pectoral nerve communicates with?
a) Medial pectoral nerve
b) Axillary nerve
c) Musculocutaneous nerve
d) Radial nerve
Explanation: The lateral pectoral nerve communicates with medial pectoral nerve around clavipectoral fascia, forming a nerve loop to pectoralis major. It does not communicate with axillary, musculocutaneous, or radial nerves. Correct answer is Medial pectoral nerve.
9. Piercing of clavipectoral fascia by vessels allows?
a) Superficial drainage
b) Nerve passage
c) Communication between axilla and pectoral region
d) Fat deposition
Explanation: Piercing of the fascia by thoracoacromial vessels and nerves allows communication between axilla and pectoral region and passage of nerves and vessels to superficial muscles. Correct answer is Communication between axilla and pectoral region.
10. Subclavius muscle pierces clavipectoral fascia?
a) Yes
b) No
c) Partially
d) Only medial fibers
Explanation: The subclavius muscle lies enclosed within the clavipectoral fascia; it does not pierce it. Only nerves and vessels pierce the fascia. Correct answer is No.
Topic: Upper Limb Nerves
Subtopic: Median Nerve and Branches
Keyword Definitions:
Anterior interosseous nerve: A branch of the median nerve, supplying deep flexors of the forearm and pronator quadratus.
Median nerve: Formed by medial and lateral cords, supplies most forearm flexors and hand muscles.
Radial nerve: A major nerve of the posterior arm, supplying extensors of the forearm and hand.
Ulnar nerve: Supplies intrinsic hand muscles and some forearm flexors.
Axillary nerve: Supplies deltoid and teres minor muscles, and shoulder sensation.
Lead Question - 2014
Anterior interosseous nerve is a branch of?
a) Radial nerve
b) Median nerve
c) Ulnar nerve
d) Axillary nerve
Explanation: The anterior interosseous nerve arises from the median nerve just below the elbow. It supplies flexor pollicis longus, lateral half of flexor digitorum profundus, and pronator quadratus. It does not provide cutaneous innervation. Therefore, the correct answer is Median nerve, which gives this important motor branch.
Guessed Questions
1. The anterior interosseous nerve supplies all except?
a) Flexor pollicis longus
b) Pronator quadratus
c) Flexor digitorum superficialis
d) Flexor digitorum profundus (lateral half)
Explanation: The anterior interosseous nerve supplies FPL, pronator quadratus, and the lateral half of FDP. Flexor digitorum superficialis is supplied by the median nerve but not its anterior interosseous branch. Thus, the correct answer is Flexor digitorum superficialis.
2. A patient with anterior interosseous nerve injury is unable to?
a) Flex distal phalanx of thumb
b) Flex proximal phalanx of thumb
c) Extend wrist
d) Abduct thumb
Explanation: Anterior interosseous nerve injury causes weakness in flexor pollicis longus, leading to inability to flex the distal phalanx of the thumb. Proximal flexion is intact, wrist extension involves radial nerve, and thumb abduction involves radial/median nerves. Thus, the correct answer is Flex distal phalanx of thumb.
3. A clinical sign of anterior interosseous nerve palsy is?
a) Ape thumb deformity
b) Hand of benediction
c) Pinch sign
d) Claw hand
Explanation: In anterior interosseous nerve palsy, patients cannot form a tip-to-tip pinch between thumb and index finger due to loss of FPL and FDP function. Instead, they approximate pads of fingers. This is called the Pinch sign, characteristic of AIN injury.
4. The median nerve in the forearm gives rise to?
a) Anterior interosseous nerve
b) Posterior interosseous nerve
c) Musculocutaneous nerve
d) Lateral pectoral nerve
Explanation: The median nerve gives off the anterior interosseous nerve below the elbow. The posterior interosseous is a branch of the radial nerve, musculocutaneous comes from the lateral cord, and lateral pectoral is from the lateral cord. Correct answer is Anterior interosseous nerve.
5. A patient with deep forearm pain and weakness of pinch grip but no sensory loss most likely has -
a) Median nerve lesion
b) Ulnar nerve lesion
c) Anterior interosseous nerve lesion
d) Radial nerve lesion
Explanation: Anterior interosseous nerve is purely motor. Its lesion causes deep forearm pain, loss of pinch grip, but no cutaneous sensory loss. Median and ulnar nerve lesions include sensory changes, radial nerve causes wrist drop. Correct answer is Anterior interosseous nerve lesion.
6. Flexor digitorum profundus is supplied by -
a) Median nerve alone
b) Ulnar nerve alone
c) Median and ulnar nerves
d) Radial nerve
Explanation: Flexor digitorum profundus has dual innervation. Lateral half (index and middle fingers) by anterior interosseous nerve (median), medial half (ring and little fingers) by ulnar nerve. Hence, correct answer is Median and ulnar nerves.
7. The anterior interosseous nerve runs along which artery?
a) Radial artery
b) Anterior interosseous artery
c) Posterior interosseous artery
d) Ulnar artery
Explanation: The anterior interosseous nerve runs on the anterior surface of the interosseous membrane, accompanying the anterior interosseous artery, a branch of the ulnar artery. Correct answer is Anterior interosseous artery.
8. Injury to anterior interosseous nerve affects which movement?
a) Thumb extension
b) Index finger DIP flexion
c) Wrist flexion
d) Elbow extension
Explanation: The anterior interosseous nerve supplies the lateral half of FDP, flexing DIP of index and middle fingers. Injury impairs DIP flexion of index finger. Wrist flexion is preserved by FCR, thumb extension by radial nerve, elbow extension by radial nerve. Correct answer is Index finger DIP flexion.
9. The "OK sign" test is used to diagnose -
a) Ulnar nerve palsy
b) Radial nerve palsy
c) Anterior interosseous nerve palsy
d) Axillary nerve palsy
Explanation: In anterior interosseous nerve palsy, the patient cannot form a circle using thumb and index finger tips, producing a flat "OK sign." This is diagnostic of Anterior interosseous nerve palsy. Other nerve lesions present with different clinical signs.
10. A 40-year-old with forearm fracture develops inability to flex thumb IP and index DIP joints, but no sensory loss. Which nerve is injured?
a) Ulnar nerve
b) Anterior interosseous nerve
c) Radial nerve
d) Musculocutaneous nerve
Explanation: Loss of thumb IP and index DIP flexion with no sensory loss indicates anterior interosseous nerve injury, as it supplies FPL and FDP lateral half. Ulnar nerve causes sensory loss, radial nerve affects extensors, musculocutaneous supplies arm flexors. Correct answer is Anterior interosseous nerve.
Subtopic: Neurotransmitter Receptors
Keyword Definitions:
• Ionic receptors: Ligand-gated ion channels that mediate fast synaptic transmission.
• NMDA: A subtype of glutamate receptor functioning as an ion channel.
• Kainate: Ionotropic glutamate receptor subtype controlling sodium influx.
• mGluR: Metabotropic glutamate receptor linked to G-proteins, not ionotropic.
• AMPA: Ionotropic glutamate receptor mediating fast excitatory transmission.
Lead Question - 2013
Ionic receptors are all except ?
a) NMDA
b) Kainate
c) mGluR
d) AMPA
Explanation: Ionotropic receptors are ligand-gated ion channels such as NMDA, Kainate, and AMPA, which mediate rapid excitatory synaptic transmission. Metabotropic glutamate receptors (mGluRs) are G-protein coupled receptors, slower in action and not ionic. Hence, the correct answer is c) mGluR.
1) Guess Question:
Which receptor subtype is blocked by magnesium at rest?
a) AMPA
b) NMDA
c) Kainate
d) mGluR
Explanation: NMDA receptors are blocked by magnesium ions at resting potential. Depolarization removes the block, allowing calcium and sodium influx. This mechanism is crucial for synaptic plasticity. Answer: b) NMDA.
2) Guess Question:
Which receptor subtype mediates most fast excitatory neurotransmission in CNS?
a) NMDA
b) AMPA
c) GABA-A
d) Glycine
Explanation: AMPA receptors mediate the majority of fast excitatory synaptic responses in the central nervous system by allowing sodium influx when glutamate binds. Answer: b) AMPA.
3) Guess Question:
Which neurotransmitter activates NMDA, AMPA, and Kainate receptors?
a) Acetylcholine
b) Glutamate
c) GABA
d) Glycine
Explanation: Glutamate is the major excitatory neurotransmitter in the CNS. It binds to NMDA, AMPA, and Kainate receptors, mediating excitatory neurotransmission and plasticity. Answer: b) Glutamate.
4) Guess Question:
A 65-year-old patient with Alzheimer’s disease benefits from memantine because it blocks:
a) GABA-A
b) NMDA
c) AMPA
d) Kainate
Explanation: Memantine is an NMDA receptor antagonist that reduces excitotoxicity caused by excessive glutamate activity in Alzheimer’s disease. Answer: b) NMDA.
5) Guess Question:
Which receptor subtype is a G-protein coupled receptor (GPCR)?
a) NMDA
b) AMPA
c) Kainate
d) mGluR
Explanation: Metabotropic glutamate receptors (mGluRs) are GPCRs that activate second messenger systems. They are not ionotropic receptors. Answer: d) mGluR.
6) Guess Question:
Inhibition of which receptor improves seizure control in epilepsy?
a) NMDA
b) AMPA
c) Kainate
d) All of the above
Explanation: Excitatory glutamate receptors like NMDA, AMPA, and Kainate are involved in seizure generation. Blocking them reduces excitability, making d) All of the above correct.
7) Guess Question:
A patient with excessive glutamate release may develop:
a) Excitotoxicity
b) Bradycardia
c) Hypoglycemia
d) Alkalosis
Explanation: Excessive glutamate activates ionotropic receptors like NMDA, leading to calcium overload and neuronal damage called excitotoxicity, common in stroke and trauma. Answer: a) Excitotoxicity.
8) Guess Question:
Which ion is mainly conducted by AMPA receptors?
a) Calcium
b) Sodium
c) Potassium
d) Chloride
Explanation: AMPA receptors mainly conduct sodium ions into the neuron, causing depolarization. Some AMPA subtypes may also allow calcium entry. Answer: b) Sodium.
9) Guess Question:
NMDA receptor activation requires binding of:
a) Glutamate only
b) Glycine only
c) Glutamate and glycine
d) GABA
Explanation: NMDA receptors require co-agonist binding of glutamate and glycine for activation. This dual requirement ensures controlled calcium influx. Answer: c) Glutamate and glycine.
10) Guess Question:
A patient on phencyclidine (PCP) shows psychotic symptoms due to blockade of:
a) NMDA receptors
b) AMPA receptors
c) Kainate receptors
d) mGluRs
Explanation: PCP blocks NMDA receptors, impairing glutamate transmission and causing dissociative and psychotic symptoms. Answer: a) NMDA receptors.
Chapter: Cerebral Circulation
Topic: Regulation of Cerebral Blood Flow
Subtopic: Effect of Exercise
Keyword Definitions:
• Cerebral blood flow: Volume of blood passing through 100g of brain tissue per minute, normally about 50 ml/100g/min.
• Autoregulation: Brain maintains constant blood flow despite blood pressure variations.
• Moderate exercise: Physical activity that increases heart rate moderately without excessive oxygen debt.
• Hypercapnia: Increased CO₂ levels, a strong regulator of cerebral blood flow.
• Hypoxia: Low oxygen, also increases cerebral blood flow.
Lead Question - 2013
What is the effect of moderate exercise on cerebral blood flow?
a) Does not change
b) Increases
c) Decreases
d) Initially decreases then increases
Explanation: During moderate exercise, cerebral blood flow remains unchanged due to autoregulation. Increased blood pressure and cardiac output are balanced by cerebral vasoconstriction, keeping flow constant. Correct answer: Does not change.
1) Which factor has the most potent effect on cerebral blood flow?
a) Oxygen
b) Carbon dioxide
c) Hydrogen ions
d) Nitric oxide
Explanation: Cerebral blood flow is most strongly influenced by arterial carbon dioxide concentration. Even slight increases in PaCO₂ cause marked vasodilation. Correct answer: Carbon dioxide.
2) A patient with head injury develops hypoventilation. What happens to cerebral blood flow?
a) Decreases
b) Increases
c) No change
d) Biphasic response
Explanation: Hypoventilation leads to hypercapnia, which dilates cerebral vessels and increases cerebral blood flow, raising intracranial pressure. Correct answer: Increases.
3) Normal cerebral blood flow is approximately?
a) 25 ml/100g/min
b) 35 ml/100g/min
c) 50 ml/100g/min
d) 75 ml/100g/min
Explanation: Normal cerebral blood flow is about 50 ml/100g/min in adults. This ensures adequate oxygen and glucose supply to neurons. Correct answer: 50 ml/100g/min.
4) During severe hypoxia, cerebral blood flow?
a) Increases
b) Decreases
c) Remains constant
d) Initially decreases then stabilizes
Explanation: Hypoxia stimulates cerebral vasodilation to maintain oxygen supply, leading to increased cerebral blood flow. Correct answer: Increases.
5) A patient undergoing hyperventilation during neurosurgery will have?
a) Increased cerebral blood flow
b) Decreased cerebral blood flow
c) No change
d) Fluctuating response
Explanation: Hyperventilation reduces PaCO₂ (hypocapnia), causing vasoconstriction and decreased cerebral blood flow, useful in lowering intracranial pressure. Correct answer: Decreased cerebral blood flow.
6) Which artery supplies the motor cortex controlling leg movement?
a) Anterior cerebral artery
b) Middle cerebral artery
c) Posterior cerebral artery
d) Basilar artery
Explanation: The anterior cerebral artery supplies the medial aspect of cerebral hemispheres, including the motor cortex area for lower limb control. Correct answer: Anterior cerebral artery.
7) Which brain region is most sensitive to hypoxia?
a) Hippocampus
b) Thalamus
c) Cerebellum
d) Medulla
Explanation: Hippocampal neurons are highly sensitive to hypoxia and ischemia, making them vulnerable to injury in low oxygen states. Correct answer: Hippocampus.
8) A patient with ischemic stroke due to middle cerebral artery occlusion will present with?
a) Hemiplegia sparing face
b) Hemiplegia involving face and arm more
c) Hemiplegia involving leg more
d) Ataxia only
Explanation: Middle cerebral artery occlusion causes contralateral hemiplegia involving face and upper limb more than lower limb. Correct answer: Hemiplegia involving face and arm more.
9) Cerebral perfusion pressure is calculated as?
a) Mean arterial pressure + intracranial pressure
b) Mean arterial pressure - intracranial pressure
c) Systolic blood pressure - intracranial pressure
d) Diastolic blood pressure + intracranial pressure
Explanation: Cerebral perfusion pressure = MAP – ICP. Adequate CPP is vital for brain oxygenation. Correct answer: Mean arterial pressure - intracranial pressure.
10) A patient with subarachnoid hemorrhage develops vasospasm. This leads to?
a) Increased cerebral blood flow
b) Decreased cerebral blood flow
c) Normal cerebral blood flow
d) Fluctuating cerebral blood flow
Explanation: Vasospasm after subarachnoid hemorrhage narrows cerebral arteries, reducing cerebral blood flow and causing ischemia. Correct answer: Decreased cerebral blood flow.
11) Autoregulation of cerebral blood flow is effective between which mean arterial pressures?
a) 30-80 mmHg
b) 50-150 mmHg
c) 70-200 mmHg
d) 90-220 mmHg
Explanation: Cerebral autoregulation maintains constant blood flow between MAP 50–150 mmHg. Outside this range, flow varies directly with pressure. Correct answer: 50-150 mmHg.
Topic: Autonomic Nervous System
Subtopic: Sympathetic Nervous System
Keyword Definitions:
- Sympathetic Noradrenergic Fibers: Sympathetic nerve fibers that release norepinephrine to activate target organs, primarily involved in the 'fight or flight' response.
- Blood Vessels: Vessels transporting blood throughout the body, regulated by sympathetic nerves for vasoconstriction and vasodilation.
- Sweat Gland: Glands producing sweat, involved in thermoregulation, uniquely innervated by sympathetic cholinergic fibers.
- Heart: Muscular organ pumping blood, controlled by sympathetic noradrenergic fibers increasing heart rate and contractility.
- Eye: Organ of vision, with sympathetic innervation controlling pupil dilation (mydriasis).
Lead Question - 2013
Which of the following does not have sympathetic noradrenergic fibers?
a) Blood vessels
b) Sweat gland
c) Heart
d) Eye
Answer and Explanation:
The correct answer is b) Sweat gland. Unlike other sympathetic target organs that use noradrenaline, sweat glands are uniquely innervated by sympathetic cholinergic fibers. This allows acetylcholine to mediate sweat secretion during thermoregulation. Blood vessels, heart, and eye receive sympathetic noradrenergic fibers, facilitating vasoconstriction, increased cardiac output, and pupil dilation.
Guessed Questions for NEET PG:
1. Sympathetic innervation of sweat glands uses:
a) Noradrenaline
b) Acetylcholine
c) Dopamine
d) Serotonin
Explanation: The correct answer is b) Acetylcholine. Sweat glands are innervated by sympathetic cholinergic fibers, which release acetylcholine, distinguishing them from most other sympathetic targets that use noradrenaline.
2. Which of the following is a function of sympathetic noradrenergic fibers?
a) Increase salivation
b) Decrease heart rate
c) Vasoconstriction
d) Pupil constriction
Explanation: The correct answer is c) Vasoconstriction. Sympathetic noradrenergic fibers release norepinephrine, causing blood vessels to constrict, thereby increasing blood pressure during stress.
3. Sympathetic noradrenergic fibers in the eye control:
a) Lens accommodation
b) Mydriasis
c) Eyelid closure
d) Tear secretion
Explanation: The correct answer is b) Mydriasis. Sympathetic noradrenergic fibers stimulate radial muscles of the iris to dilate the pupil, aiding vision in low light.
4. Which gland uses cholinergic fibers despite being sympathetic?
a) Adrenal medulla
b) Sweat gland
c) Salivary gland
d) Lacrimal gland
Explanation: The correct answer is b) Sweat gland. Sweat glands are unique as they are innervated by sympathetic cholinergic fibers, releasing acetylcholine for thermoregulation.
5. In sympathetic stimulation, the heart responds by:
a) Decreasing rate
b) Increasing rate and contractility
c) Vasodilation
d) Secreting hormones
Explanation: The correct answer is b) Increasing rate and contractility. Sympathetic noradrenergic fibers release norepinephrine, increasing heart rate and force of contraction during stress.
6. Blood vessel constriction during sympathetic activation occurs via:
a) Cholinergic fibers
b) Adrenergic fibers
c) Dopaminergic fibers
d) Serotonergic fibers
Explanation: The correct answer is b) Adrenergic fibers. Sympathetic noradrenergic fibers release norepinephrine to stimulate vasoconstriction, increasing blood pressure during 'fight or flight' response.
7. Which of the following does not use norepinephrine in its sympathetic innervation?
a) Heart
b) Sweat gland
c) Blood vessels
d) Eye
Explanation: The correct answer is b) Sweat gland. Sweat glands use acetylcholine despite being sympathetic targets, whereas the heart, blood vessels, and eye use norepinephrine.
8. Adrenergic fibers primarily release:
a) Acetylcholine
b) Noradrenaline
c) Dopamine
d) GABA
Explanation: The correct answer is b) Noradrenaline. Adrenergic fibers, part of the sympathetic nervous system, release norepinephrine to stimulate target organs during stress responses.
9. Sympathetic control of pupil dilation involves:
a) Sphincter pupillae muscle
b) Ciliary muscle
c) Radial muscle of iris
d) Orbicularis oculi
Explanation: The correct answer is c) Radial muscle of iris. Sympathetic noradrenergic fibers stimulate the radial muscle, causing pupil dilation (mydriasis) for improved vision in dim light.
10. Sympathetic noradrenergic fibers originate from:
a) Parasympathetic ganglia
b) Sympathetic ganglia
c) Spinal cord gray matter
d) Dorsal root ganglion
Explanation: The correct answer is b) Sympathetic ganglia. Postganglionic sympathetic noradrenergic fibers arise from sympathetic ganglia and innervate target organs, releasing norepinephrine.
Topic: Autonomic Nervous System
Subtopic: Reflexes and Intracranial Pressure Regulation
Keyword Definitions:
- Cushing Reflex: A physiological nervous system response to increased intracranial pressure leading to hypertension, bradycardia, and irregular respiration.
- Intracranial Pressure (ICP): The pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull.
- Bradycardia: A slower than normal heart rate, typically less than 60 beats per minute.
- Tachypnoea: Abnormally rapid breathing.
Lead Question - 2013
Cushing reflex is associated with all except ?
a) Hypotension
b) Increased intracranial pressure
c) Bradycardia
d) Tachyponea
Answer and Explanation:
The correct answer is a) Hypotension. The Cushing reflex is a protective physiological response to increased intracranial pressure characterized by hypertension, bradycardia, and irregular or tachypnoea respiratory patterns. Hypotension is not associated with Cushing reflex. Instead, elevated ICP leads to increased systemic blood pressure to maintain cerebral perfusion.
Guessed Questions for NEET PG:
1. Which of the following is not a feature of Cushing reflex?
a) Hypertension
b) Bradycardia
c) Tachypnoea
d) Hypotension
Explanation: The correct answer is d) Hypotension. Cushing reflex results from increased intracranial pressure and leads to hypertension, bradycardia, and tachypnoea to maintain cerebral perfusion. Hypotension is not part of the reflex response.
2. The Cushing reflex is primarily a response to:
a) Hypoxia
b) Hypercapnia
c) Increased intracranial pressure
d) Dehydration
Explanation: The correct answer is c) Increased intracranial pressure. Cushing reflex activates to maintain cerebral perfusion in the face of elevated intracranial pressure by increasing systemic blood pressure, inducing bradycardia and irregular breathing.
3. Clinical manifestation of the Cushing reflex includes:
a) Tachycardia
b) Hypotension
c) Bradycardia
d) Hyperthermia
Explanation: The correct answer is c) Bradycardia. The Cushing reflex features bradycardia, hypertension, and irregular breathing, as a compensatory mechanism to maintain cerebral perfusion pressure during raised ICP.
4. Which cranial nerve is mainly involved in mediating bradycardia during Cushing reflex?
a) Trigeminal nerve
b) Vagus nerve
c) Hypoglossal nerve
d) Facial nerve
Explanation: The correct answer is b) Vagus nerve. Increased ICP stimulates the vagus nerve leading to bradycardia, as part of the Cushing reflex to balance elevated systemic blood pressure.
5. A patient with severe head injury shows high blood pressure, slow pulse, and irregular respiration. This is indicative of:
a) Cushing reflex
b) Mydriasis
c) Horner's syndrome
d) Meniere's disease
Explanation: The correct answer is a) Cushing reflex. The triad of hypertension, bradycardia, and irregular respiration signifies the body's response to high intracranial pressure to maintain cerebral blood flow.
6. A 40-year-old patient with traumatic brain injury develops bradycardia and hypertension. This reflex helps:
a) Reduce ICP
b) Increase cerebral perfusion
c) Decrease cerebral perfusion
d) Cause vasodilation
Explanation: The correct answer is b) Increase cerebral perfusion. The Cushing reflex increases systemic arterial pressure to counteract elevated intracranial pressure, thereby preserving cerebral perfusion.
7. Tachypnoea in Cushing reflex is due to:
a) Metabolic acidosis
b) Medullary ischemia
c) Hyperventilation
d) Hypoxia
Explanation: The correct answer is b) Medullary ischemia. Increased ICP compresses the medulla, leading to irregular respiratory patterns or tachypnoea as part of the Cushing reflex.
8. In Cushing reflex, systemic hypertension occurs to:
a) Increase cardiac output
b) Reduce heart rate
c) Maintain cerebral perfusion
d) Stimulate sweat glands
Explanation: The correct answer is c) Maintain cerebral perfusion. Systemic hypertension compensates for high ICP, ensuring adequate oxygen and nutrient delivery to the brain despite compression.
9. Which part of the brain senses increased ICP in Cushing reflex?
a) Hypothalamus
b) Medulla oblongata
c) Cerebellum
d) Thalamus
Explanation: The correct answer is b) Medulla oblongata. The medulla senses increased intracranial pressure, triggering autonomic responses like bradycardia and hypertension to maintain cerebral blood flow.
10. Which of the following is not part of Cushing's triad?
a) Hypertension
b) Bradycardia
c) Tachypnoea
d) Hypothermia
Explanation: The correct answer is d) Hypothermia. Cushing's triad includes hypertension, bradycardia, and irregular or tachypnoea respiration. Hypothermia is unrelated to the reflex response.
Topic: Hypothalamic Regulation
Subtopic: Orexigenic Neurons
Keyword Definitions:
Orexigenic Neurons: Neurons that stimulate appetite and increase food intake.
Dorsal Raphae: Nucleus in brainstem involved in serotonin production.
Locus Coeruleus: Brainstem nucleus involved in noradrenaline production.
Lateral Hypothalamic Area: Hypothalamic region promoting feeding behavior.
Hippocampus: Brain structure involved in memory formation.
Lead Question - 2013
Cell bodies of orexigenic neurons are present in?
a) Dorsal raphae
b) Locus coeruleus
c) Lateral hypothalamic area
d) Hippocampus
Answer & Explanation:
Answer: c) Lateral hypothalamic area.
Orexigenic neurons, which promote appetite, are primarily located in the lateral hypothalamic area. These neurons stimulate food intake by releasing neuropeptides that act on various brain regions. Dysfunction in this area may lead to eating disorders such as anorexia or obesity. The correct answer is lateral hypothalamic area.
1. Guessed Question
Which neurotransmitter is primarily involved in stimulating orexigenic neurons?
a) Dopamine
b) Norepinephrine
c) Neuropeptide Y
d) Serotonin
Answer & Explanation:
Answer: c) Neuropeptide Y.
Neuropeptide Y (NPY) is a powerful orexigenic neurotransmitter that stimulates food intake and reduces energy expenditure. It is synthesized in the hypothalamus and acts on various brain regions to promote hunger. Increased NPY activity is associated with increased appetite and obesity, while decreased levels relate to anorexia.
2. Guessed Question
Destruction of the lateral hypothalamic area causes:
a) Hyperphagia
b) Aphagia
c) Polydipsia
d) Polyuria
Answer & Explanation:
Answer: b) Aphagia.
Destruction of the lateral hypothalamic area leads to aphagia, which is the inability or refusal to eat. This area is crucial for hunger signaling. Damage to this region results in severe anorexia and weight loss. Therefore, the correct answer is aphagia, indicating its role in promoting food intake.
3. Guessed Question
Which of the following is NOT a function of the hypothalamus?
a) Regulation of hunger
b) Thermoregulation
c) Visual processing
d) Water balance regulation
Answer & Explanation:
Answer: c) Visual processing.
The hypothalamus regulates hunger, thirst, body temperature, and circadian rhythms but does not participate directly in visual processing. Visual information is processed by the occipital lobe and visual cortex. Therefore, visual processing is not a function of the hypothalamus, making it the correct choice for this question.
4. Guessed Question
Which hormone released by the hypothalamus stimulates appetite?
a) Leptin
b) Ghrelin
c) Insulin
d) Cortisol
Answer & Explanation:
Answer: b) Ghrelin.
Ghrelin, secreted by the stomach, acts on the hypothalamus to stimulate appetite and promote food intake. It increases before meals and decreases after food consumption. High ghrelin levels are associated with increased hunger and potential weight gain, while low levels relate to appetite suppression.
5. Guessed Question
Orexigenic neurons are activated during:
a) Postprandial state
b) Fasting state
c) Sleep
d) Physical exercise
Answer & Explanation:
Answer: b) Fasting state.
During fasting, orexigenic neurons in the lateral hypothalamic area become activated, increasing the secretion of hunger-promoting neuropeptides like NPY and AgRP. This stimulates appetite and encourages food-seeking behavior, aiming to restore energy balance. Therefore, the correct answer is fasting state.
6. Guessed Question
Which peptide inhibits orexigenic neurons?
a) Agouti-related peptide (AgRP)
b) Leptin
c) Neuropeptide Y (NPY)
d) Melanin-concentrating hormone (MCH)
Answer & Explanation:
Answer: b) Leptin.
Leptin, secreted by adipose tissue, inhibits orexigenic neurons and promotes satiety. High leptin levels signal sufficient energy stores, decreasing appetite. In obesity, leptin resistance may develop, impairing this regulation. Therefore, leptin is the key hormone that suppresses orexigenic neuronal activity.
7. Guessed Question
Orexigenic neurons primarily release which of the following?
a) Dopamine
b) Agouti-related peptide (AgRP)
c) Acetylcholine
d) GABA
Answer & Explanation:
Answer: b) Agouti-related peptide (AgRP).
Orexigenic neurons release Agouti-related peptide (AgRP) and neuropeptide Y (NPY), which stimulate appetite by antagonizing melanocortin receptors in the hypothalamus. These peptides promote feeding and reduce energy expenditure. Hence, AgRP is correctly identified as a primary mediator of orexigenic neuron action.
8. Guessed Question
Which clinical condition is associated with damage to the lateral hypothalamic area?
a) Obesity
b) Anorexia
c) Hypertension
d) Diabetes insipidus
Answer & Explanation:
Answer: b) Anorexia.
Damage to the lateral hypothalamic area causes severe anorexia and aphagia, leading to weight loss. This area is critical for hunger signaling. Absence of its function impairs the body's ability to initiate feeding behavior, resulting in decreased food intake and energy imbalance.
9. Guessed Question
Which of the following statements is true about orexigenic neurons?
a) Inhibit food intake
b) Located in hippocampus
c) Promote feeding behavior
d) Located in dorsal raphae
Answer & Explanation:
Answer: c) Promote feeding behavior.
Orexigenic neurons stimulate appetite and promote food intake by releasing neuropeptides such as NPY and AgRP. Located in the lateral hypothalamic area, they are activated during energy deficit states. Their primary role is to encourage feeding, contrasting with anorexigenic neurons that suppress appetite.
10. Guessed Question
Leptin resistance is commonly observed in:
a) Anorexia nervosa
b) Obesity
c) Hypothyroidism
d) Addison's disease
Answer & Explanation:
Answer: b) Obesity.
Leptin resistance occurs when high leptin levels fail to suppress appetite, commonly observed in obesity. This condition prevents adequate feedback to the hypothalamus, causing continued food intake despite sufficient energy stores. It is a key factor in the pathophysiology of obesity, leading to further weight gain.
Topic: Visual System
Subtopic: Retina and Photoreceptors
Keywords:
• Retina: Light-sensitive layer at the back of the eye.
• Cones: Photoreceptor cells responsible for color vision and visual acuity.
• Photoreceptor: Specialized cell that responds to light.
• Visual System: Structures and pathways involved in vision.
Lead Question - 2013 (September 2008)
Number of cones in Retina?
a) 3-5 millions
b) 10-20 millions
c) 25-50 millions
d) 50-100 millions
Answer and Explanation:
Correct answer is a) 3-5 millions. The human retina contains approximately 3 to 5 million cone photoreceptors concentrated in the central region called the fovea. These cones enable high-resolution color vision under bright light (photopic) conditions and are essential for tasks requiring fine visual detail. (50 words)
1. Rod cells are responsible for:
a) Color vision
b) Low-light vision
c) High-resolution vision
d) Motion detection
Explanation:
Rod cells are specialized for low-light (scotopic) vision, providing black and white images in dim conditions, with high sensitivity but low spatial resolution. (Answer: b)
2. Fovea centralis contains predominantly:
a) Rods
b) Cones
c) Bipolar cells
d) Ganglion cells
Explanation:
The fovea centralis contains the highest concentration of cone cells, essential for sharp central vision and color discrimination in bright light. (Answer: b)
3. Cone cells are most sensitive to which type of light?
a) Dim light
b) Bright light
c) Infrared light
d) Ultraviolet light
Explanation:
Cone cells function optimally in bright light conditions, enabling high acuity and color perception. (Answer: b)
4. Total number of rod cells in human retina is approximately:
a) 120 million
b) 6 million
c) 3 million
d) 1 million
Explanation:
The human retina contains around 120 million rod cells, which mediate vision in low-light conditions and are more numerous than cone cells. (Answer: a)
5. The three types of cones are sensitive to:
a) Red, Green, Blue wavelengths
b) Ultraviolet, Infrared, Visible
c) Alpha, Beta, Gamma
d) Rod, Cone, Bipolar
Explanation:
Cone cells are categorized into three types based on spectral sensitivity to red (long), green (medium), and blue (short) wavelengths, enabling color vision. (Answer: a)
6. Clinical condition related to cone dysfunction is called:
a) Night blindness
b) Color blindness
c) Glaucoma
d) Cataract
Explanation:
Color blindness is caused by defective or absent cone cells, impairing color discrimination, typically inherited and most commonly affecting red-green perception. (Answer: b)
7. Which layer of retina contains photoreceptors?
a) Ganglion cell layer
b) Inner nuclear layer
c) Outer nuclear layer
d) Plexiform layer
Explanation:
The photoreceptors, including rods and cones, are located in the outer nuclear layer of the retina, where they transduce light into neural signals. (Answer: c)
8. Cone density is maximum at:
a) Optic disc
b) Peripheral retina
c) Fovea centralis
d) Macula lutea
Explanation:
Cone density peaks in the fovea centralis, the central region of the retina, responsible for sharp and detailed central vision. (Answer: c)
9. Cone cells mediate which type of vision?
a) Scotopic
b) Photopic
c) Mesopic
d) None
Explanation:
Cone cells mediate photopic vision, functioning under bright light conditions, essential for color perception and high visual acuity. (Answer: b)
10. Cone dysfunction may lead to which of the following disorders?
a) Glaucoma
b) Achromatopsia
c) Retinitis pigmentosa
d) Optic neuritis
Explanation:
Achromatopsia is a congenital condition caused by cone dysfunction, resulting in color blindness, poor visual acuity, and photophobia. (Answer: b)
Topic: Motor System
Subtopic: Corticospinal Tract and Precentral Gyrus
Keywords:
• Precentral Gyrus: Brain region responsible for voluntary motor control.
• Corticospinal Tract: Major pathway transmitting motor commands from brain to spinal cord.
• Vision: Sensory perception of light and images.
• Olfaction: Sense of smell.
• Auditory: Related to hearing.
• Voluntary Movement: Conscious control of skeletal muscles.
Lead Question - 2013 (September 2008)
Precentral gyrus & corticospinal tract are essential for?
a) Vision
b) Olfaction
c) Auditory
d) Voluntary movement
Answer and Explanation:
Correct answer is d) Voluntary movement. The precentral gyrus (primary motor cortex) initiates voluntary movements, and the corticospinal tract transmits these motor signals from the cortex to the spinal motor neurons, enabling conscious control of muscle activity. This system is critical for purposeful and coordinated bodily movements. (50 words)
1. The primary function of the precentral gyrus is:
a) Sensory perception
b) Voluntary motor control
c) Balance regulation
d) Speech comprehension
Explanation:
The precentral gyrus, part of the frontal lobe, controls voluntary skeletal muscle movements by sending motor commands through the corticospinal tract. (Answer: b)
2. Corticospinal tract primarily carries:
a) Sensory signals
b) Autonomic signals
c) Voluntary motor commands
d) Reflex arcs
Explanation:
The corticospinal tract transmits voluntary motor commands from the precentral gyrus to spinal cord neurons, enabling conscious muscle control. (Answer: c)
3. Lesion of precentral gyrus causes:
a) Blindness
b) Loss of voluntary movement
c) Loss of smell
d) Hearing loss
Explanation:
Damage to the precentral gyrus results in paralysis or weakness of voluntary muscles contralateral to the lesion, as it is the primary motor cortex. (Answer: b)
4. Corticospinal tract decussation occurs at:
a) Midbrain
b) Medulla
c) Pons
d) Spinal cord
Explanation:
The corticospinal tract crosses (decussates) at the medullary pyramids, ensuring contralateral control of voluntary motor functions. (Answer: b)
5. Damage to corticospinal tract leads to:
a) Sensory loss
b) Muscle atrophy
c) Spastic paralysis
d) Loss of consciousness
Explanation:
Lesions of the corticospinal tract often produce spastic paralysis, characterized by increased muscle tone and exaggerated reflexes. (Answer: c)
6. Voluntary movement requires integration of:
a) Sensory input and motor commands
b) Reflex actions only
c) Autonomic responses
d) Visual stimuli alone
Explanation:
Voluntary movements involve integrating sensory inputs and motor commands from the precentral gyrus and other brain regions to execute precise actions. (Answer: a)
7. Corticospinal tract is also known as:
a) Pyramidal tract
b) Extrapyramidal tract
c) Spinothalamic tract
d) Vestibulospinal tract
Explanation:
The corticospinal tract is called the pyramidal tract due to its passage through the medullary pyramids and its critical role in voluntary movement control. (Answer: a)
8. Clinical sign of upper motor neuron lesion is:
a) Flaccid paralysis
b) Spasticity and hyperreflexia
c) Muscle fasciculations
d) Decreased tone
Explanation:
Upper motor neuron lesions affecting the corticospinal tract typically cause spasticity and hyperreflexia, due to loss of inhibitory control. (Answer: b)
9. Which lobe contains the precentral gyrus?
a) Parietal
b) Temporal
c) Frontal
d) Occipital
Explanation:
The precentral gyrus is located in the frontal lobe and houses the primary motor cortex responsible for voluntary motor control. (Answer: c)
10. The primary neurotransmitter of corticospinal neurons is:
a) Dopamine
b) Acetylcholine
c) Norepinephrine
d) GABA
Explanation:
Corticospinal neurons use glutamate as the primary excitatory neurotransmitter, but acetylcholine is released at the neuromuscular junction by lower motor neurons. (Answer: b)
Topic: Reflexes
Subtopic: Conditioned Reflex
Keywords:
• Conditioned Reflex: A learned response to a previously neutral stimulus.
• Reinforcement: Process of strengthening a conditioned response.
• Habituation: Decreased response to a repeated benign stimulus.
• Innate Reflex: Inborn automatic response to a stimulus.
Lead Question - 2013 (September 2008)
Salivation of dog when food is given along with bell is?
a) Conditioned reflex
b) Reinforcement
c) Habituation
d) Innate reflex
Answer and Explanation:
Correct answer is a) Conditioned reflex. Pavlov’s experiment demonstrated that a neutral stimulus (bell) when paired with food becomes a conditioned stimulus, leading to salivation as a conditioned reflex. This is a classic example of learned behavior where the dog salivates to the bell alone after conditioning. (50 words)
1. Classical conditioning was first demonstrated by?
a) Skinner
b) Pavlov
c) Watson
d) Thorndike
Explanation:
Ivan Pavlov first demonstrated classical conditioning through experiments with dogs, showing that a neutral stimulus paired with food can trigger a conditioned reflex. (Answer: b)
2. In conditioned reflex, the stimulus-response association is:
a) Innate
b) Learned
c) Genetic
d) Random
Explanation:
Conditioned reflex involves a learned association between a neutral stimulus and a biologically significant stimulus, resulting in a new behavioral response. (Answer: b)
3. Reinforcement in conditioning is used to:
a) Weaken response
b) Strengthen conditioned response
c) Remove stimulus
d) Introduce habit
Explanation:
Reinforcement strengthens the conditioned reflex by increasing the probability that the conditioned response occurs following the conditioned stimulus. (Answer: b)
4. Habituation leads to:
a) Increased response
b) Unchanged response
c) Decreased response to repeated stimulus
d) Conditioned reflex formation
Explanation:
Habituation is a process where the organism gradually decreases its response to a harmless stimulus when presented repeatedly over time. (Answer: c)
5. Example of innate reflex is:
a) Pavlov's dog salivation
b) Knee jerk reflex
c) Learning to read
d) Phobia formation
Explanation:
An innate reflex, like the knee jerk reflex, is a pre-programmed automatic response not dependent on prior learning or experience. (Answer: b)
6. Which part of the brain is critical for conditioned reflex?
a) Cerebellum
b) Hypothalamus
c) Cerebral Cortex
d) Medulla
Explanation:
The cerebral cortex is primarily responsible for conditioned reflex formation by integrating sensory input and associating new stimulus-response patterns. (Answer: c)
7. Pavlov’s experiment demonstrated which type of learning?
a) Operant conditioning
b) Classical conditioning
c) Observational learning
d) Habituation
Explanation:
Pavlov’s dog experiment is a seminal example of classical conditioning, where a neutral stimulus paired with an unconditioned stimulus elicits a conditioned response. (Answer: b)
8. A neutral stimulus becomes a conditioned stimulus when:
a) It naturally triggers a response
b) It is repeatedly paired with an unconditioned stimulus
c) It is presented alone
d) It loses its effect
Explanation:
A neutral stimulus becomes conditioned by being repeatedly paired with an unconditioned stimulus until it elicits the response on its own. (Answer: b)
9. Conditioned reflex differs from innate reflex because:
a) Both are genetically programmed
b) Conditioned reflex is learned, innate is inborn
c) Innate reflex involves reinforcement
d) Conditioned reflex is involuntary
Explanation:
Conditioned reflex is acquired through learning and experience, whereas innate reflexes are inborn and do not require learning or practice. (Answer: b)
10. An example of conditioned reflex in humans is:
a) Sneezing
b) Salivating to the smell of food
c) Knee jerk
d) Cough reflex
Explanation:
Salivating at the smell or sight of food is a conditioned reflex in humans, where a neutral stimulus becomes associated with food anticipation. (Answer: b)
Topic: Cerebellum
Subtopic: Cerebellar Nuclei Functions
Keywords:
• Cerebellar Nucleus: A deep collection of nerve cells in the cerebellum that processes input and output signals.
• Caudate Nucleus: Part of basal ganglia involved in motor control and learning.
• Subthalamic Nucleus: Basal ganglia structure involved in movement regulation.
• Fastigial Nucleus: A deep cerebellar nucleus involved in balance and posture control.
• Putamen: Basal ganglia nucleus important for motor skills.
Lead Question - 2013 (September 2008)
Which of the following is a cerebellar nucleus?
a) Caudate nucleus
b) Subthalamic nucleus
c) Fastigial nucleus
d) Putamen
Answer and Explanation:
Correct answer is c) Fastigial nucleus. The fastigial nucleus is one of the deep cerebellar nuclei involved in the coordination of balance and posture. It processes input from the cerebellar cortex and integrates vestibular and proprioceptive signals. Other choices are part of the basal ganglia, not cerebellum. (50 words)
1. The dentate nucleus is associated with:
a) Muscle tone regulation
b) Planning of voluntary movements
c) Sensory perception
d) Reflex actions
Explanation:
The dentate nucleus, largest of the cerebellar nuclei, is involved in planning, initiation, and control of voluntary movements by connecting the cerebellum with motor areas of the cerebral cortex. (Answer: b)
2. Which is not a cerebellar deep nucleus?
a) Fastigial
b) Globus pallidus
c) Interposed
d) Dentate
Explanation:
Globus pallidus is part of the basal ganglia, not cerebellar nuclei. Cerebellar deep nuclei include fastigial, interposed, and dentate nuclei, important for motor control. (Answer: b)
3. Lesion in fastigial nucleus may lead to:
a) Ataxia
b) Loss of fine touch
c) Aphasia
d) Visual field defect
Explanation:
Lesions in the fastigial nucleus affect posture and balance, causing ataxia due to disrupted vestibulocerebellar connections. (Answer: a)
4. Interposed nucleus controls:
a) Muscle tone
b) Limb movement coordination
c) Visual processing
d) Auditory perception
Explanation:
Interposed nucleus (globose and emboliform) plays a role in regulating limb movement coordination and fine motor control via cerebellar pathways. (Answer: b)
5. The primary function of cerebellar nuclei is to:
a) Generate motor commands
b) Relay and modulate signals from cerebellar cortex
c) Process sensory input
d) Regulate consciousness
Explanation:
Cerebellar nuclei relay and modulate signals from the cerebellar cortex to motor areas, integrating sensory and motor information to coordinate movement. (Answer: b)
6. Cerebellar damage presents clinically with:
a) Hemiplegia
b) Dysmetria
c) Aphasia
d) Hemianopia
Explanation:
Cerebellar damage leads to dysmetria—impaired control of movement range and force—due to disrupted coordination, especially from deep nuclei dysfunction. (Answer: b)
7. Which is true about dentate nucleus?
a) It is involved in posture regulation
b) Largest cerebellar nucleus
c) Receives input from vestibular apparatus
d) Controls spinal reflexes
Explanation:
The dentate nucleus is the largest cerebellar nucleus and is primarily involved in the planning and initiation of voluntary movements. (Answer: b)
8. Cerebellar nuclei send output via:
a) Spinothalamic tract
b) Superior cerebellar peduncle
c) Inferior cerebellar peduncle
d) Medial lemniscus
Explanation:
Cerebellar nuclei send efferent output via the superior cerebellar peduncle, mainly targeting thalamus and motor cortex to regulate movement. (Answer: b)
9. Damage to subthalamic nucleus causes:
a) Hemiballismus
b) Ataxia
c) Aphasia
d) Hypotonia
Explanation:
Lesions in the subthalamic nucleus cause hemiballismus—a unilateral, involuntary flinging movement of limbs—due to basal ganglia dysfunction, not cerebellar. (Answer: a)
10. The cerebellar vermis is involved in:
a) Cognitive processing
b) Eye movement control
c) Body posture and locomotion
d) Hearing pathways
Explanation:
Cerebellar vermis contributes to control of axial muscles, body posture, and locomotion, integrating sensory inputs and motor coordination via cerebellar nuclei. (Answer: c)
Topic: Thalamus and Basal Ganglia
Subtopic: Thalamic Nuclei Functions
Keywords:
• Thalamic Nuclei: Relay centers in the brain transmitting sensory and motor signals.
• Basal Ganglia: Brain structures involved in movement control and coordination.
• Lateral Dorsal Nucleus: Thalamic relay nucleus involved in limbic system connections.
• Pulvinar: Thalamic nucleus involved in visual processing.
• Ventral Anterior Nucleus: Thalamic nucleus linked with motor control circuits.
• Intralaminar Nuclei: Group of thalamic nuclei involved in arousal, awareness, and basal ganglia function.
Lead Question - 2013 (September 2008)
Which thalamic nuclei can produce basal ganglia symptoms?
a) Lateral dorsal
b) Pulvinar
c) Ventral anterior
d) Intralaminar
Answer and Explanation:
Correct answer is d) Intralaminar. The intralaminar thalamic nuclei are involved in connecting the basal ganglia with the cortex and play a critical role in modulating motor function and awareness. Lesions in these nuclei can lead to symptoms mimicking basal ganglia dysfunction such as movement disorders or altered consciousness. (50 words)
1. The basal ganglia includes all except:
a) Caudate nucleus
b) Putamen
c) Thalamus
d) Globus pallidus
Explanation:
Thalamus is not part of the basal ganglia but acts as a relay station, whereas caudate, putamen, and globus pallidus are core basal ganglia structures involved in motor control. (Answer: c)
2. Lesion in ventral anterior nucleus causes:
a) Sensory loss
b) Movement disorder
c) Visual impairment
d) Hearing loss
Explanation:
Ventral anterior nucleus is part of the motor thalamus and its lesion typically results in movement disorders due to disrupted motor control pathways. (Answer: b)
3. Which pathway connects basal ganglia to cortex via thalamus?
a) Corticospinal tract
b) Corticothalamic pathway
c) Pallidothalamic tract
d) Spinothalamic tract
Explanation:
Pallidothalamic tract connects globus pallidus of basal ganglia to the thalamus, modulating motor signals relayed to the cortex. (Answer: c)
4. Lesions in intralaminar nuclei cause:
a) Aphasia
b) Basal ganglia symptoms
c) Cerebellar ataxia
d) Visual field defects
Explanation:
Intralaminar nuclei are connected to basal ganglia circuits; damage can cause movement disorders resembling basal ganglia disease. (Answer: b)
5. Pulvinar nucleus mainly affects:
a) Motor function
b) Visual processing
c) Sensory perception
d) Speech production
Explanation:
Pulvinar nucleus is primarily involved in visual processing and higher visual functions, not basal ganglia symptoms. (Answer: b)
6. Lateral dorsal nucleus connects primarily with:
a) Motor cortex
b) Limbic system
c) Visual cortex
d) Brainstem
Explanation:
Lateral dorsal nucleus is part of the limbic thalamic group, involved in emotional and memory functions, not basal ganglia symptoms. (Answer: b)
7. Basal ganglia symptoms include:
a) Bradykinesia
b) Aphasia
c) Hemianopia
d) Anosmia
Explanation:
Bradykinesia, or slowed movement, is a cardinal feature of basal ganglia dysfunction due to impaired modulation of motor circuits. (Answer: a)
8. Intralaminar nuclei receive input from:
a) Cerebral cortex
b) Brainstem reticular formation
c) Cerebellum
d) Peripheral nerves
Explanation:
Intralaminar nuclei receive extensive input from brainstem reticular formation and basal ganglia, crucial for arousal and motor coordination. (Answer: b)
9. Thalamic syndrome includes:
a) Motor weakness
b) Sensory loss with pain
c) Visual field defects
d) Aphasia
Explanation:
Thalamic syndrome is typically characterized by contralateral sensory loss with severe pain due to lesions in thalamic sensory relay nuclei. (Answer: b)
10. Basal ganglia is primarily involved in:
a) Memory processing
b) Voluntary motor control
c) Visual acuity
d) Hearing perception
Explanation:
Basal ganglia play a key role in voluntary motor control, movement initiation, and coordination, not in sensory processing like vision or hearing. (Answer: b)
Topic: Sympathetic Nervous System
Subtopic: Control of Sweat Glands
Keywords:
• Sweating: Process of producing sweat to regulate body temperature.
• Norepinephrine: Neurotransmitter involved in sympathetic nervous responses.
• Epinephrine: Hormone and neurotransmitter involved in fight or flight response.
• Acetylcholine: Neurotransmitter in both parasympathetic and sympathetic nervous systems.
• Histamine: Chemical involved in allergic reactions and inflammation.
Lead Question - 2013 (September 2008)
Sweating is mediated by ?
a) Norepinephrine
b) Epinephrine
c) Acetylcholine
d) Histamine
Answer and Explanation:
Correct answer is c) Acetylcholine. Unlike most sympathetic postganglionic neurons that release norepinephrine, sweat glands are activated by acetylcholine acting on muscarinic receptors. This unique exception allows thermoregulatory sweating to occur, especially in response to increased body temperature or emotional stress. (50 words)
1. Sympathetic preganglionic fibers release:
a) Acetylcholine
b) Norepinephrine
c) Epinephrine
d) Dopamine
Explanation:
Sympathetic preganglionic fibers always release acetylcholine at synapses with postganglionic neurons, stimulating them to release norepinephrine or acetylcholine depending on the target tissue. (Answer: a)
2. Which receptor type mediates sweating?
a) Alpha-1 adrenergic
b) Beta-2 adrenergic
c) Muscarinic cholinergic
d) Nicotinic cholinergic
Explanation:
Sweating is mediated by muscarinic cholinergic receptors on sweat glands activated by acetylcholine, differing from typical adrenergic sympathetic responses. (Answer: c)
3. In hyperhidrosis, excessive sweating is primarily due to:
a) Increased norepinephrine
b) Increased acetylcholine
c) Decreased dopamine
d) Decreased epinephrine
Explanation:
Hyperhidrosis is commonly caused by overactivity of cholinergic sympathetic fibers, leading to excessive acetylcholine release and profuse sweating. (Answer: b)
4. Sweat glands controlled by sympathetic system are called:
a) Apocrine glands
b) Eccrine glands
c) Sebaceous glands
d) Ceruminous glands
Explanation:
Eccrine sweat glands, responsible for thermoregulation, are controlled by the sympathetic nervous system via acetylcholine release onto muscarinic receptors. (Answer: b)
5. Which is not a function of sweating?
a) Temperature regulation
b) Excretion of toxins
c) Lubrication of skin
d) pH regulation
Explanation:
Sweating primarily regulates body temperature and eliminates waste; however, lubrication of skin is a function of sebaceous glands, not sweat glands. (Answer: c)
6. Emotional sweating is mediated by which part of nervous system?
a) Parasympathetic
b) Somatic
c) Sympathetic
d) Central
Explanation:
Emotional sweating is mediated by the sympathetic nervous system via cholinergic stimulation of eccrine glands, independent of thermoregulatory needs. (Answer: c)
7. Histamine acts primarily in:
a) Sweat gland stimulation
b) Vasodilation and allergic reactions
c) Muscle contraction
d) Thermoregulation
Explanation:
Histamine is involved in allergic responses and vasodilation but does not play a direct role in mediating sweat gland activity. (Answer: b)
8. Which is true regarding acetylcholine's role in the ANS?
a) Only released in parasympathetic pathways
b) Released in both sympathetic and parasympathetic pathways
c) Only released in somatic motor neurons
d) Not involved in ANS
Explanation:
Acetylcholine is the neurotransmitter at all preganglionic synapses and at parasympathetic postganglionic synapses, as well as for sympathetic postganglionic innervation of sweat glands. (Answer: b)
9. Dysfunction in acetylcholine receptors causes which condition?
a) Myasthenia gravis
b) Hyperthyroidism
c) Diabetes mellitus
d) Hypotension
Explanation:
Myasthenia gravis is an autoimmune disorder targeting acetylcholine receptors, leading to muscle weakness and impaired neuromuscular transmission. (Answer: a)
10. Eccrine sweat gland stimulation is predominantly:
a) Adrenergic
b) Cholinergic
c) Dopaminergic
d) Serotonergic
Explanation:
Eccrine sweat glands are stimulated by cholinergic fibers in the sympathetic nervous system, releasing acetylcholine onto muscarinic receptors. (Answer: b)
Topic: Cerebrospinal Fluid (CSF) Composition
Subtopic: Electrolyte Concentrations in CSF and Plasma
Keywords:
• Cerebrospinal fluid (CSF): Clear fluid surrounding brain and spinal cord, providing protection.
• Plasma: The liquid component of blood carrying cells and proteins.
• Electrolytes: Ions like Na+, K+, Cl-, Ca2+, important for cell function.
• Glucose: Primary energy source in body fluids.
• Bicarbonate (HCO3-): Important for pH buffering in body fluids.
Lead Question - 2013 (September 2008)
Which of the following has same concentration in CSF and plasma ?
a) Ca2+
b) HCO3
c) Glucose
d) Cl-
Answer and Explanation:
Correct answer is d) Cl-. Chloride ion concentration in CSF is approximately equal to plasma because it crosses the blood-brain barrier more freely compared to other ions. Ca2+, HCO3 and glucose are regulated and have different concentrations in CSF vs plasma to maintain CNS homeostasis. (50 words)
1. The main function of CSF is:
a) Oxygen transport
b) Nutrient delivery
c) Mechanical protection and chemical stability
d) Hormone transport
Explanation:
The primary function of CSF is to cushion the brain and spinal cord, maintain chemical stability, and remove waste products. It provides mechanical protection and optimal ionic environment for neuronal function. (Answer: c)
2. CSF is produced mainly by:
a) Arachnoid villi
b) Choroid plexus
c) Ependymal cells
d) Subarachnoid space
Explanation:
The majority of CSF is produced by the choroid plexus within the ventricles of the brain through selective filtration and active secretion mechanisms. (Answer: b)
3. Glucose concentration in CSF compared to plasma is generally:
a) Equal
b) Higher
c) Lower
d) Zero
Explanation:
CSF glucose concentration is typically about two-thirds of plasma glucose concentration due to restricted transport across the blood-brain barrier. (Answer: c)
4. In bacterial meningitis, CSF glucose level is usually:
a) Increased
b) Normal
c) Decreased
d) Unchanged
Explanation:
In bacterial meningitis, CSF glucose level typically decreases because bacteria consume glucose and inflammation impairs glucose transport across the blood-brain barrier. (Answer: c)
5. The blood-brain barrier allows easy passage of which ion into CSF?
a) K+
b) Na+
c) Cl-
d) Protein
Explanation:
Chloride ions (Cl-) can pass relatively freely across the blood-brain barrier, hence their concentrations in plasma and CSF are approximately equal. (Answer: c)
6. Bicarbonate concentration in CSF compared to plasma is:
a) Same
b) Lower
c) Higher
d) Zero
Explanation:
Bicarbonate concentration in CSF is slightly lower than in plasma due to selective transport, contributing to pH regulation in the CNS. (Answer: b)
7. Calcium concentration in CSF is generally:
a) Equal to plasma
b) Higher than plasma
c) Lower than plasma
d) Zero
Explanation:
Calcium concentration in CSF is lower than in plasma because tight regulation prevents excess calcium influx, protecting neurons from excitotoxicity. (Answer: c)
8. In which condition would CSF protein be markedly elevated?
a) Viral meningitis
b) Bacterial meningitis
c) Hypoglycemia
d) Hypocalcemia
Explanation:
CSF protein levels are markedly elevated in bacterial meningitis due to increased permeability of the blood-brain barrier and inflammation. (Answer: b)
9. The osmolarity of CSF compared to plasma is:
a) Lower
b) Higher
c) Equal
d) Variable
Explanation:
Osmolarity of CSF is nearly equal to plasma, maintained by regulated ion transport to preserve CNS homeostasis and prevent neuronal dysfunction. (Answer: c)
10. Which of the following is not a function of CSF?
a) Mechanical cushioning
b) Nutrient supply
c) Waste removal
d) Blood oxygen transport
Explanation:
CSF provides mechanical cushioning, supplies nutrients, and removes waste, but oxygen transport is primarily carried out by blood, not CSF. (Answer: d)
Topic: Reflex Actions
Subtopic: Withdrawal Reflex
Keywords:
• Withdrawal reflex: An automatic response to a painful stimulus to protect the body.
• Flexion: Bending a limb towards the body.
• Extension: Straightening a limb away from the body.
• Polysynaptic reflex: Reflex involving multiple synapses.
• Protective reflex: Prevents injury by removing body part from harm.
Lead Question - 2013 (September 2008)
What is seen in withdrawal reflex ?
a) Extension
b) Flexion
c) Extension followed by flexion
d) None of the above
Answer and Explanation:
Correct answer is b) Flexion. The withdrawal reflex is a protective polysynaptic reflex resulting in the flexion of a limb when exposed to a painful stimulus. This action helps rapidly remove the body part from harm. It involves sensory neurons, interneurons, and motor neurons. (50 words)
1. The withdrawal reflex primarily involves which type of neurons?
a) Sensory and motor only
b) Sensory, interneurons, and motor
c) Only motor neurons
d) Only sensory neurons
Explanation:
The withdrawal reflex is polysynaptic and involves sensory neurons detecting the painful stimulus, interneurons in the spinal cord transmitting the signal, and motor neurons triggering the flexor muscles to contract and withdraw the limb. (Answer: b)
2. Clinically, exaggerated withdrawal reflex indicates:
a) Normal response
b) Upper motor neuron lesion
c) Lower motor neuron lesion
d) Spinal shock
Explanation:
An exaggerated withdrawal reflex may suggest an upper motor neuron lesion, indicating disinhibition of spinal reflexes. It points toward a lack of supraspinal modulation. (Answer: b)
3. In the withdrawal reflex, the contralateral limb shows:
a) Flexion
b) Extension
c) No response
d) Tremors
Explanation:
During the withdrawal reflex, the crossed extensor reflex causes the contralateral limb to extend, providing balance and support when the affected limb withdraws from the painful stimulus. (Answer: b)
4. The withdrawal reflex is mediated at the level of the:
a) Brain
b) Spinal cord
c) Brainstem
d) Peripheral nerve
Explanation:
The withdrawal reflex is primarily mediated at the spinal cord level, allowing for rapid response without cortical involvement, which ensures speed and efficiency in protecting the body from harmful stimuli. (Answer: b)
5. In clinical testing, absence of the withdrawal reflex may indicate:
a) Upper motor neuron lesion
b) Lower motor neuron lesion
c) Normal finding
d) Hyperreflexia
Explanation:
An absent withdrawal reflex may suggest a lower motor neuron lesion, indicating damage to peripheral nerves or the spinal cord segment responsible for reflex arc, impairing the protective response. (Answer: b)
6. The speed of the withdrawal reflex is typically:
a) Very slow
b) Intermediate
c) Rapid
d) Variable
Explanation:
The withdrawal reflex is rapid to promptly remove the body part from painful stimuli, preventing injury. Its speed is enhanced by short reflex pathways and minimal synapses involved. (Answer: c)
7. Flexor muscles involved in withdrawal reflex are activated via:
a) Direct sensory neuron connections
b) Interneurons
c) Brain control
d) Hormonal signaling
Explanation:
Flexor muscles in the withdrawal reflex are activated via interneurons in the spinal cord, which transmit the pain signal from sensory neurons to motor neurons, causing the necessary contraction. (Answer: b)
8. Painful stimulus applied to the foot initiates the withdrawal reflex causing:
a) Flexion of leg
b) Extension of leg
c) No movement
d) Opposite limb movement only
Explanation:
A painful stimulus on the foot activates sensory receptors, initiating the withdrawal reflex. This leads to flexion of the affected leg to withdraw from harm, often coupled with contralateral limb extension for support. (Answer: a)
9. The withdrawal reflex is classified as:
a) Monosynaptic reflex
b) Polysynaptic reflex
c) Cranial reflex
d) Voluntary reflex
Explanation:
The withdrawal reflex is a polysynaptic reflex involving multiple interneurons and synapses, unlike monosynaptic reflexes like the knee jerk. This complexity allows for integration and modulation of the response. (Answer: b)
10. Which neurotransmitter is primarily involved in the withdrawal reflex?
a) Acetylcholine
b) Dopamine
c) Glutamate
d) GABA
Explanation:
Glutamate is the primary excitatory neurotransmitter involved in the withdrawal reflex, mediating signal transmission between sensory neurons, interneurons, and motor neurons in the spinal cord to activate muscle contraction. (Answer: c)
Topic: Cerebral Circulation
Subtopic: Cerebral Blood Flow (CBF)
Keywords:
• Cerebral blood flow (CBF): The volume of blood passing through the brain per unit time.
• ml/min: Milliliters per minute, unit of flow rate.
• Autoregulation: Brain's mechanism to maintain constant CBF despite changes in blood pressure.
• Ischemia: Insufficient blood flow causing tissue damage.
• Hyperemia: Increased blood flow to tissues.
Lead Question - 2013 (September 2008)
Normal cerebral blood flow in ml/min ?
a) 55
b) 150
c) 750
d) 1000
Answer and Explanation:
Correct answer is c) 750. Normal cerebral blood flow in an adult is approximately 750 ml/min, supplying essential oxygen and nutrients to brain tissue. Autoregulatory mechanisms maintain this flow across a range of systemic blood pressures. Insufficient CBF leads to ischemia, while excessive flow may cause hyperemia or edema. (50 words)
1. Cerebral autoregulation maintains constant blood flow at what mean arterial pressure range?
a) 50-150 mmHg
b) 70-110 mmHg
c) 90-160 mmHg
d) 40-120 mmHg
Explanation:
Cerebral autoregulation preserves stable cerebral blood flow despite systemic blood pressure changes, within a mean arterial pressure range of approximately 50–150 mmHg. Outside this range, autoregulation fails, risking ischemia or hyperemia. (Answer: a)
2. Which condition decreases cerebral blood flow?
a) Hypercapnia
b) Hypotension
c) Fever
d) Exercise
Explanation:
Hypotension reduces cerebral perfusion pressure, impairing blood flow to the brain, risking ischemia. Hypercapnia and fever increase cerebral blood flow, while exercise generally increases systemic flow, also enhancing cerebral perfusion. (Answer: b)
3. The major factor increasing cerebral blood flow is:
a) Hypocapnia
b) Hypercapnia
c) Hypothermia
d) Hypoxia
Explanation:
Hypercapnia (elevated CO2 levels) dilates cerebral vessels, significantly increasing cerebral blood flow. Hypocapnia causes vasoconstriction and reduces flow. Hypoxia increases flow as compensatory, but hypercapnia remains the primary regulator. (Answer: b)
4. Clinical correlation: In head trauma, monitoring cerebral perfusion pressure is vital because:
a) Prevents seizures
b) Avoids ischemia
c) Controls temperature
d) Reduces intracranial pressure
Explanation:
Monitoring cerebral perfusion pressure ensures adequate blood flow, preventing ischemic injury in traumatic brain injury. Insufficient perfusion worsens neuronal damage, while elevated pressure risks herniation. Seizures and temperature control are secondary considerations. (Answer: b)
5. In ischemic stroke, cerebral blood flow is typically:
a) Increased
b) Normal
c) Severely reduced
d) Unchanged
Explanation:
Ischemic stroke results from arterial blockage, leading to a marked decrease in cerebral blood flow to the affected region, risking permanent neuronal damage unless promptly reperfused. (Answer: c)
6. The primary unit of cerebral blood flow measurement is:
a) ml/min
b) ml/100g/min
c) mmHg
d) L/min
Explanation:
Cerebral blood flow is typically expressed in ml/100g/min to account for brain mass differences, though absolute flow in ml/min is also used. (Answer: b)
7. Hyperemia in the brain is caused by:
a) Hypocapnia
b) Hypoxia
c) Low blood glucose
d) Low body temperature
Explanation:
Hyperemia results from vasodilation, triggered by hypoxia or increased metabolic demand. Hypocapnia causes vasoconstriction, reducing flow, while hypoglycemia and low temperature reduce metabolic rate and flow. (Answer: b)
8. Normal cerebral blood flow per 100 grams of brain tissue is approximately:
a) 20-25 ml/min
b) 50-55 ml/min
c) 10-15 ml/min
d) 60-70 ml/min
Explanation:
Normal cerebral blood flow is around 50-55 ml/100g/min, ensuring adequate oxygen and nutrient supply. Values below 20 ml/100g/min risk ischemia. (Answer: b)
9. Which area of the brain has the highest blood flow?
a) White matter
b) Basal ganglia
c) Gray matter
d) Brainstem
Explanation:
Gray matter has the highest cerebral blood flow due to high metabolic demands, approximately 80 ml/100g/min, compared to white matter. This supports active neuronal processing. (Answer: c)
10. In conditions of chronic hypertension, cerebral autoregulation curve:
a) Shifts left
b) Shifts right
c) Remains unchanged
d) Becomes steeper
Explanation:
Chronic hypertension shifts the autoregulatory curve rightward, meaning higher pressures are needed to maintain normal cerebral blood flow, increasing risk of hypoperfusion if aggressive BP lowering occurs. (Answer: b)
Topic: Motor Pathways
Subtopic: Spinal Tracts and Motor Control
Keywords:
• Spinal pathway: Neural routes in the spinal cord conducting motor and sensory signals.
• Fine motor activity: Precise movements involving small muscles, e.g., fingers.
• Rubrospinal tract: Motor pathway from red nucleus involved in fine motor control.
• Vestibulospinal tract: Maintains posture and balance.
• Reticulospinal tract: Coordinates locomotion and postural control.
Lead Question - 2013 (September 2008)
Spinal pathway mainly regulating fine motor activity ?
a) Anterior corticospinal tract
b) Rubrospinal tract
c) Vestibulospinal tract
d) Reticulospinal tract
Answer and Explanation:
Correct answer is b) Rubrospinal tract. The rubrospinal tract originates in the red nucleus of midbrain and primarily controls fine motor activities of upper limbs, especially hand and fingers. It complements corticospinal control, while vestibulospinal and reticulospinal tracts are involved in posture and gross movements. (50 words)
1. The primary role of vestibulospinal tract is:
a) Fine motor control
b) Postural stability
c) Pain modulation
d) Conscious sensation
Explanation:
The vestibulospinal tract originates from vestibular nuclei and facilitates postural stability and balance, particularly in standing and walking. It does not participate in fine motor control or sensory functions, which are mediated by other pathways like corticospinal tract and sensory tracts. (Answer: b)
2. Which tract is most involved in voluntary fine motor movement?
a) Rubrospinal tract
b) Corticospinal tract
c) Reticulospinal tract
d) Vestibulospinal tract
Explanation:
The corticospinal tract is the most important for voluntary fine motor movement, particularly in distal muscles of limbs, although the rubrospinal tract supports fine motor control. Reticulospinal and vestibulospinal tracts are mainly involved in posture and gross movements. (Answer: b)
3. Damage to the rubrospinal tract results in:
a) Loss of pain sensation
b) Impaired fine motor control
c) Loss of balance
d) Hyperreflexia
Explanation:
The rubrospinal tract modulates fine motor control, particularly in upper limbs. Lesions here impair precise hand and finger movements. It does not affect pain sensation, balance, or cause hyperreflexia directly, which involve different pathways. (Answer: b)
4. Reticulospinal tract primarily controls:
a) Fine motor activity
b) Reflex arcs
c) Postural control and locomotion
d) Visual processing
Explanation:
The reticulospinal tract plays a major role in regulating posture and locomotion by modulating motor neurons controlling axial and proximal limb muscles. It does not govern fine motor skills, visual processing, or direct reflex arcs. (Answer: c)
5. Which of the following is NOT a function of the anterior corticospinal tract?
a) Voluntary movement of axial muscles
b) Fine distal limb control
c) Postural muscle control
d) Gross motor movements
Explanation:
Anterior corticospinal tract mainly controls axial and proximal muscles and contributes to posture and gross movements. Fine distal limb control is primarily by the lateral corticospinal tract, not anterior. (Answer: b)
6. Clinical correlation: A patient with midbrain stroke exhibits loss of fine motor control in upper limbs. The likely affected tract is:
a) Corticospinal tract
b) Vestibulospinal tract
c) Rubrospinal tract
d) Reticulospinal tract
Explanation:
Midbrain stroke may damage the rubrospinal tract, impairing fine upper limb movements. The corticospinal tract is more affected in cortical or spinal lesions. Vestibulospinal and reticulospinal tracts control posture and gross movements, not fine motor skills. (Answer: c)
7. Rubrospinal tract decussates at:
a) Medulla
b) Pons
c) Midbrain
d) Spinal cord
Explanation:
The rubrospinal tract decussates in the midbrain at the level of the red nucleus before descending in the lateral funiculus of the spinal cord. This decussation enables contralateral control of upper limb fine motor functions. (Answer: c)
8. The primary neurotransmitter of rubrospinal tract is:
a) Acetylcholine
b) Glutamate
c) GABA
d) Dopamine
Explanation:
The rubrospinal tract primarily uses glutamate as its neurotransmitter to stimulate motor neurons involved in fine control of limb muscles. Acetylcholine is used in neuromuscular junctions, and dopamine is mainly modulatory in basal ganglia pathways. (Answer: b)
9. The role of corticospinal tract vs rubrospinal tract is:
a) Both control gross movements
b) Both control fine motor activity equally
c) Corticospinal dominates fine motor; rubrospinal supports
d) Neither involved in fine motor control
Explanation:
The corticospinal tract is the primary pathway for voluntary fine motor control, especially of distal limbs. The rubrospinal tract acts as an auxiliary pathway supporting upper limb fine motor function, especially when corticospinal pathways are compromised. (Answer: c)
10. A lesion affecting the red nucleus primarily impacts:
a) Pain sensation
b) Proprioception
c) Fine motor control
d) Temperature sensation
Explanation:
The red nucleus gives rise to the rubrospinal tract, which modulates fine motor control of upper limbs. A lesion here results in impaired hand and finger movements, not pain or temperature sensation. (Answer: c)
Topic: Sensory Physiology
Subtopic: Mechanoreceptors
Keywords:
• Ruffini end organ: Slowly adapting mechanoreceptors detecting sustained skin stretch and pressure.
• Sensation: The process by which sensory receptors detect stimuli and transmit them to the brain.
• Sustained pressure: Continuous mechanical force applied to the skin over time.
• Heat receptors: Thermoreceptors detecting temperature changes.
• Touch receptors: Mechanoreceptors detecting light touch and pressure.
Lead Question - 2013 (September 2008)
Ruffini end organ is associated with sensation of:
a) Sustained Pressure
b) Heat
c) Touch
d) None of the above
Answer and Explanation:
Correct answer is a) Sustained Pressure. Ruffini endings are slow-adapting mechanoreceptors located in the dermis and joint capsules. They respond to skin stretch and continuous pressure, contributing to proprioception and detection of object manipulation. Heat is detected by thermoreceptors and touch by Meissner or Merkel corpuscles.
1. Meissner’s corpuscles detect:
a) Vibration
b) Light touch
c) Sustained pressure
d) Pain
Explanation:
Meissner's corpuscles are rapidly adapting mechanoreceptors present in glabrous skin. They are highly sensitive to light touch and low-frequency vibration, not sustained pressure or pain. Ruffini endings detect sustained pressure, while pain is sensed by free nerve endings. (Answer: b)
2. Pacinian corpuscles are primarily sensitive to:
a) Temperature
b) Sustained pressure
c) High-frequency vibration
d) Pain
Explanation:
Pacinian corpuscles are large encapsulated mechanoreceptors detecting high-frequency vibration and deep pressure. They adapt quickly and are not involved in detecting sustained pressure or pain. Ruffini endings are responsible for sustained pressure. (Answer: c)
3. Clinical case: Loss of Ruffini endings results in impairment of:
a) Pain perception
b) Temperature sensation
c) Proprioception and sustained pressure sensation
d) Light touch sensation
Explanation:
Ruffini endings contribute to proprioception and sustained pressure detection. Their loss impairs object manipulation and joint position sense, affecting fine motor skills. Pain and temperature remain unaffected as they are mediated by free nerve endings and thermoreceptors. (Answer: c)
4. Thermoreceptors primarily detect:
a) Sustained pressure
b) Temperature changes
c) Vibration
d) Light touch
Explanation:
Thermoreceptors are specialized nerve endings that detect temperature changes, signaling warmth or cold. Ruffini endings detect sustained pressure, while Meissner and Pacinian corpuscles detect touch and vibration respectively. Free nerve endings detect both pain and temperature. (Answer: b)
5. Which receptor helps in detecting skin stretch and joint position?
a) Meissner corpuscle
b) Pacinian corpuscle
c) Ruffini end organ
d) Merkel disc
Explanation:
Ruffini endings are mechanoreceptors detecting sustained skin stretch and joint capsule deformation, contributing to proprioception. Meissner and Pacinian corpuscles detect touch and vibration. Merkel discs detect sustained light touch. (Answer: c)
6. Merkel discs are associated with:
a) Pain
b) Sustained light touch
c) Vibration
d) Temperature
Explanation:
Merkel discs are slow-adapting mechanoreceptors found in basal epidermis, responsible for detecting sustained light touch and pressure. They do not detect pain, temperature, or vibration. (Answer: b)
7. A patient with joint position sense defect likely has damaged:
a) Meissner corpuscles
b) Ruffini end organs
c) Free nerve endings
d) Pacinian corpuscles
Explanation:
Ruffini end organs in joint capsules are essential for proprioception, detecting joint position and skin stretch. Damage leads to impaired position sense, whereas Meissner and Pacinian corpuscles do not contribute significantly to proprioception. (Answer: b)
8. Which of the following is NOT a function of Ruffini end organ?
a) Detect sustained pressure
b) Detect temperature
c) Detect skin stretch
d) Aid proprioception
Explanation:
Ruffini end organs detect sustained pressure, skin stretch, and contribute to proprioception. Temperature detection is the function of thermoreceptors, not Ruffini endings. (Answer: b)
9. Clinical correlation: In diabetic neuropathy, which receptor's dysfunction leads to impaired fine touch?
a) Ruffini end organ
b) Merkel disc
c) Free nerve endings
d) Pacinian corpuscle
Explanation:
Merkel discs mediate fine touch and pressure. Diabetic neuropathy often impairs these receptors, resulting in decreased touch sensitivity. Ruffini endings are less commonly affected in early stages. (Answer: b)
10. Receptors involved in proprioception include:
a) Free nerve endings
b) Meissner corpuscle
c) Muscle spindles and Ruffini end organs
d) Pacinian corpuscles
Explanation:
Proprioception depends on inputs from muscle spindles and Ruffini end organs in joint capsules. These receptors detect muscle stretch and skin/joint position, providing essential feedback for movement coordination. Free nerve endings detect pain, not proprioception. (Answer: c)
Topic: Sensory Physiology
Subtopic: Pain Perception Mechanism
Keywords:
• Pain receptors: Specialized nerve endings that detect noxious stimuli causing pain sensation.
• Meissner's corpuscle: Mechanoreceptors sensitive to light touch, located in dermal papillae.
• Pacinian corpuscle: Mechanoreceptors detecting deep pressure and vibration.
• Free nerve endings: Unencapsulated nerve endings detecting pain, temperature, and crude touch.
• Merkel disc: Slowly adapting mechanoreceptors detecting sustained touch and pressure.
Lead Question - 2013 (September 2008)
Pain receptors are?
a) Meissners corpuscle
b) Pacinian corpuscle
c) Free nerve endings
d) Merkel disc
Answer and Explanation:
The correct answer is c) Free nerve endings. These are unencapsulated nerve endings distributed widely in skin, mucosa, and organs. They are responsible for detecting pain (nociception) by responding to mechanical, chemical, or thermal noxious stimuli. Other options detect touch or pressure, not pain directly.
1. Which receptor is primarily responsible for light touch sensation?
a) Pacinian corpuscle
b) Meissner's corpuscle
c) Free nerve endings
d) Merkel disc
Explanation:
Meissner's corpuscles are rapidly adapting mechanoreceptors located in dermal papillae of glabrous skin. They are highly sensitive to light touch and vibrations of low frequency. Free nerve endings do not primarily detect light touch but rather pain and temperature changes. (Answer: b)
2. Clinical relevance: Patient presents with loss of pain sensation. Which receptor type is most likely damaged?
a) Pacinian corpuscle
b) Merkel disc
c) Free nerve endings
d) Meissner's corpuscle
Explanation:
Free nerve endings are responsible for detecting pain and temperature changes. Damage to these fibers can result in analgesia, making patients unable to perceive harmful stimuli, thereby increasing injury risk. Pacinian corpuscles and Merkel discs are not directly involved in pain perception. (Answer: c)
3. Which receptor is NOT involved in mechanoreception?
a) Meissner's corpuscle
b) Pacinian corpuscle
c) Free nerve endings
d) Merkel disc
Explanation:
Free nerve endings are primarily responsible for detecting pain and temperature, not fine touch or pressure. Meissner's, Pacinian, and Merkel receptors are mechanoreceptors responsible for various touch and pressure sensations. Hence, free nerve endings are not involved in mechanoreception. (Answer: c)
4. In clinical practice, which receptor dysfunction causes numbness but preserves pain sensation?
a) Meissner's corpuscle
b) Free nerve endings
c) Pacinian corpuscle
d) Merkel disc
Explanation:
Meissner's corpuscles and Pacinian corpuscles dysfunction result in loss of fine touch and vibration perception, but pain and temperature sensation remain intact due to free nerve endings. Pure loss of fine touch without pain indicates mechanoreceptor-specific dysfunction. (Answer: a)
5. Which receptor type helps in proprioception, not pain sensation?
a) Meissner's corpuscle
b) Pacinian corpuscle
c) Free nerve endings
d) Muscle spindle
Explanation:
Muscle spindles are specialized mechanoreceptors that provide information on muscle stretch and proprioception. Free nerve endings detect pain, whereas Meissner’s and Pacinian corpuscles detect light touch and vibration, not position sense. (Answer: d)
6. Free nerve endings detect:
a) Light touch
b) Temperature and pain
c) Pressure
d) Vibration
Explanation:
Free nerve endings are unencapsulated sensory receptors widely distributed and specialized for detecting temperature variations and nociceptive (painful) stimuli. They are key in transmitting painful sensations from peripheral tissues to the CNS. (Answer: b)
7. Which receptor is encapsulated and sensitive to deep pressure?
a) Free nerve endings
b) Merkel disc
c) Pacinian corpuscle
d) Meissner's corpuscle
Explanation:
Pacinian corpuscles are large, encapsulated mechanoreceptors highly sensitive to deep pressure and high-frequency vibration. They do not respond to pain stimuli, which is the function of free nerve endings. (Answer: c)
8. Pathological loss of pain sensation indicates damage to?
a) Merkel disc
b) Pacinian corpuscle
c) Free nerve endings
d) Meissner's corpuscle
Explanation:
Pathological loss of pain sensation, termed analgesia, typically occurs when free nerve endings are damaged. These receptors detect harmful mechanical, chemical, or thermal stimuli. Damage to other receptor types affects touch and pressure, not pain. (Answer: c)
9. Merkel discs are primarily responsible for detecting:
a) Pain
b) Fine touch
c) Vibration
d) Temperature
Explanation:
Merkel discs are slowly adapting mechanoreceptors located in the basal epidermis, responsible for detecting sustained light touch and pressure. They do not participate in pain sensation, which is mediated by free nerve endings. (Answer: b)
10. Clinical case: Patient with small-fiber neuropathy shows impaired pain sensation. Which fibers are affected?
a) Group Aβ fibers
b) Group Aα fibers
c) Free nerve endings
d) Meissner's corpuscle
Explanation:
Small-fiber neuropathy typically affects unmyelinated or thinly myelinated fibers, including free nerve endings responsible for pain and temperature. Group Aβ and Aα fibers mediate touch and proprioception, not pain. (Answer: c)
Topic: Autonomic Nervous System
Subtopic: Nerve Fiber Classification
Keywords:
• Group B nerve fibers: Myelinated fibers with medium diameter, conducting impulses at 3-15 m/s.
• Sympathetic preganglionic fibers: Nerve fibers that originate from the spinal cord and synapse in ganglia.
• Parasympathetic preganglionic fibers: Nerve fibers from brainstem or sacral spinal cord synapsing in ganglia near target organs.
• Postganglionic fibers: Nerve fibers that emerge from autonomic ganglia to innervate target tissues.
Lead Question - 2013 (September 2008)
Group B nerve fibers are?
a) Sympathetic preganglionic
b) Sympathetic postganglionic
c) Parasympathetic preganglionic
d) Parasympathetic postganglionic
Answer and Explanation:
The correct answer is a) Sympathetic preganglionic. Group B nerve fibers are myelinated with a moderate diameter and conduct impulses at speeds between 3 to 15 meters per second. They are predominantly found in the autonomic nervous system as preganglionic fibers, which transmit signals from the spinal cord to ganglia before reaching the target organ.
1. In NEET PG exams, which nerve fiber type is classified as Group A?
a) Preganglionic sympathetic
b) Postganglionic sympathetic
c) Motor fibers to skeletal muscle
d) Sensory fibers from skin
Explanation:
Group A fibers are large-diameter, myelinated nerve fibers conducting impulses rapidly at over 15 m/s. These fibers include somatic motor fibers that innervate skeletal muscles and sensory fibers transmitting touch and proprioception. They differ from Group B fibers, which are preganglionic autonomic fibers transmitting signals to autonomic ganglia. (Answer: c)
2. Clinical significance of damaged Group B fibers?
a) Loss of skeletal muscle movement
b) Impaired autonomic preganglionic transmission
c) Loss of pain sensation
d) None
Explanation:
Damage to Group B fibers impairs autonomic nervous system preganglionic transmission, leading to dysregulation of autonomic functions like heart rate, digestion, and temperature control. Skeletal muscle movement remains unaffected because Group A fibers mediate voluntary muscle control. Pain sensation is conveyed via different sensory fibers. (Answer: b)
3. Which statement is false regarding Group B fibers?
a) Myelinated
b) High conduction velocity
c) Found in autonomic pathways
d) Preganglionic
Explanation:
Group B fibers are myelinated and preganglionic but have moderate, not high, conduction velocity compared to Group A fibers. They conduct impulses at 3–15 m/s, appropriate for autonomic functions but slower than somatic motor fibers. This moderate speed suits their role in autonomic signal transmission. (Answer: b)
4. Parasympathetic preganglionic fibers are classified as?
a) Group A
b) Group B
c) Group C
d) None
Explanation:
Parasympathetic preganglionic fibers belong to Group B fibers. These are myelinated with moderate diameter and conduct impulses at 3–15 m/s. They project from the CNS to parasympathetic ganglia near target organs. Postganglionic fibers in the parasympathetic system are Group C fibers, unmyelinated and slower. (Answer: b)
5. Sympathetic postganglionic fibers are?
a) Group A
b) Group B
c) Group C
d) Group D
Explanation:
Sympathetic postganglionic fibers are classified as Group C fibers. These are unmyelinated and conduct impulses slowly (0.5–2 m/s). They connect the autonomic ganglia to target organs, regulating functions such as vasoconstriction and sweat gland activation, making them distinct from myelinated preganglionic Group B fibers. (Answer: c)
6. Clinical scenario: A patient with autonomic dysfunction shows reduced preganglionic activity. Which fibers are affected?
a) Group A
b) Group B
c) Group C
d) None
Explanation:
Autonomic dysfunction due to reduced preganglionic activity implicates Group B fibers. These fibers transmit signals from the CNS to autonomic ganglia. Dysfunction here causes impaired control of heart rate, digestion, and other involuntary processes. Postganglionic fibers (Group C) are not primarily affected. (Answer: b)
7. Which fibers are responsible for fast pain transmission?
a) Group Aδ
b) Group B
c) Group C
d) Group Aβ
Explanation:
Group Aδ fibers transmit fast pain signals. They are myelinated and conduct impulses at around 12–30 m/s, providing rapid sharp pain perception. Group B fibers do not transmit pain signals; they are preganglionic autonomic fibers. Group C fibers transmit slow, dull pain. (Answer: a)
8. In a case of diabetic autonomic neuropathy, which fibers are commonly damaged?
a) Group A
b) Group B
c) Group C
d) None
Explanation:
Diabetic autonomic neuropathy primarily affects Group C fibers—unmyelinated postganglionic fibers responsible for autonomic regulation. Group B fibers are generally less vulnerable but may also be involved. Damage leads to symptoms like orthostatic hypotension, gastroparesis, and abnormal sweating. (Answer: c)
9. Which fibers connect CNS to autonomic ganglia?
a) Group A
b) Group B
c) Group C
d) Group D
Explanation:
Group B fibers connect the central nervous system to autonomic ganglia. These are myelinated fibers with moderate diameter and conduction speed (3–15 m/s). They serve as preganglionic fibers in both sympathetic and parasympathetic divisions. Postganglionic fibers are mainly Group C. (Answer: b)
10. Clinical case: Patient has impaired heart rate regulation due to preganglionic fiber damage. Which group is involved?
a) Group A
b) Group B
c) Group C
d) None
Explanation:
Heart rate regulation impairment due to preganglionic fiber damage involves Group B fibers. These myelinated fibers transmit autonomic signals from the CNS to autonomic ganglia, influencing cardiac function. Postganglionic (Group C) fibers affect target organ response but do not transmit CNS signals to ganglia. (Answer: b)
Topic: Autonomic Nervous System
Subtopic: Parasympathetic Nervous System
Keyword Definitions:
- Post-ganglionic fibers: Nerve fibers extending from autonomic ganglia to target organs.
- Parasympathetic Nervous System: Part of the autonomic system responsible for "rest and digest" responses.
- A fibers: Myelinated fibers classified by diameter and conduction velocity.
- C fibers: Small diameter, unmyelinated fibers with slow conduction velocity.
Lead Question - 2013
Post-ganglionic parasympathetic fibers are - (September 2008)
a) A a
b) A (3
c) A 7
d) C
Answer & Explanation:
Correct Answer: d) C
Post-ganglionic parasympathetic fibers are predominantly small-diameter unmyelinated C fibers. These fibers conduct impulses slowly and are responsible for transmitting signals from autonomic ganglia to effector organs, regulating functions such as secretion, smooth muscle contraction, and vasodilation in the "rest and digest" state.
1. Which fibers have the fastest conduction velocity?
a) A fibers
b) B fibers
c) C fibers
d) D fibers
Answer & Explanation:
Correct Answer: a) A fibers
A fibers are myelinated and have large diameters, giving them the fastest conduction velocity among nerve fibers. This is crucial for rapid reflex actions and motor control, whereas C fibers are slow due to their unmyelinated nature.
2. The main neurotransmitter released by post-ganglionic parasympathetic fibers is:
a) Norepinephrine
b) Acetylcholine
c) Dopamine
d) Serotonin
Answer & Explanation:
Correct Answer: b) Acetylcholine
Post-ganglionic parasympathetic fibers release acetylcholine at their synapses with effector organs. Acetylcholine acts on muscarinic receptors to produce parasympathetic responses such as reduced heart rate and increased glandular secretion.
3. Clinical example of parasympathetic dysfunction:
a) Hypertension
b) Dry mouth
c) Tachycardia
d) Hyperhidrosis
Answer & Explanation:
Correct Answer: b) Dry mouth
Parasympathetic dysfunction can result in reduced glandular secretion, leading to symptoms such as dry mouth (xerostomia). It may occur due to nerve injury, diseases, or drug side effects affecting cholinergic pathways.
4. A fibers are primarily:
a) Unmyelinated
b) Large myelinated
c) Medium unmyelinated
d) Small myelinated
Answer & Explanation:
Correct Answer: b) Large myelinated
A fibers are large-diameter, myelinated fibers that conduct impulses rapidly. They are responsible for carrying motor commands and touch sensations, unlike C fibers which are slow and unmyelinated.
5. B fibers are mainly associated with:
a) Sensory pathways
b) Motor pathways
c) Preganglionic autonomic fibers
d) Postganglionic autonomic fibers
Answer & Explanation:
Correct Answer: c) Preganglionic autonomic fibers
B fibers are myelinated, preganglionic autonomic fibers with intermediate diameter and conduction speed, transmitting signals from the central nervous system to autonomic ganglia.
6. Parasympathetic nervous system is also known as:
a) Thoracolumbar system
b) Craniosacral system
c) Somatic system
d) Sympathetic system
Answer & Explanation:
Correct Answer: b) Craniosacral system
The parasympathetic system is called the craniosacral system because its preganglionic neurons originate in the brainstem (cranial nerves) and sacral spinal cord, responsible for conserving energy and promoting digestion.
7. C fibers are primarily responsible for transmitting:
a) Touch sensation
b) Pain and temperature
c) Proprioception
d) Visual input
Answer & Explanation:
Correct Answer: b) Pain and temperature
C fibers, unmyelinated and slow-conducting, are involved in transmitting pain (nociceptive) and temperature sensations from peripheral tissues to the central nervous system.
8. Damage to post-ganglionic parasympathetic fibers may cause:
a) Increased heart rate
b) Hypotension
c) Bradycardia
d) Hypersecretion
Answer & Explanation:
Correct Answer: a) Increased heart rate
Damage to post-ganglionic parasympathetic fibers impairs acetylcholine release, reducing vagal influence on the heart and resulting in unopposed sympathetic activity, thereby increasing heart rate (tachycardia).
9. The primary function of post-ganglionic parasympathetic fibers is to:
a) Prepare body for fight or flight
b) Maintain homeostasis during rest
c) Detect muscle stretch
d) Stimulate pain pathways
Answer & Explanation:
Correct Answer: b) Maintain homeostasis during rest
Post-ganglionic parasympathetic fibers mediate "rest and digest" activities, promoting digestion, energy storage, and reduced heart rate. Their slow conduction is adequate for these sustained, non-urgent functions.
10. Clinical test to assess parasympathetic function:
a) Pupillary light reflex
b) Deep tendon reflex
c) Pinprick sensation
d) Babinski sign
Answer & Explanation:
Correct Answer: a) Pupillary light reflex
Pupillary light reflex tests parasympathetic function via the oculomotor nerve (cranial nerve III). Light-induced pupil constriction reflects intact parasympathetic pathways, while absence indicates dysfunction in post-ganglionic parasympathetic fibers.
Topic: Sensory Receptors
Subtopic: Thermoreceptors
Keyword Definitions:
- Thermoreceptors: Sensory receptors that respond to temperature changes.
- CMR-1: Cold and menthol receptor-1, activated by moderate cold temperatures.
- VR1: Vanilloid receptor type 1, activated by high heat and capsaicin.
- VRL-1: Vanilloid receptor-like 1, involved in noxious heat sensing.
- VR2: Vanilloid receptor type 2, primarily involved in deep tissue temperature sensing.
Lead Question - 2013
Which receptor get stimulated in moderate cold? (September 2008)
a) CMR-1
b) VR1
c) VRL-1
d) VR2
Answer & Explanation:
Correct Answer: a) CMR-1
CMR-1 (Cold and Menthol Receptor-1) is primarily activated by moderate cold temperatures. It plays a critical role in sensing environmental temperature changes and contributes to the body's thermoregulatory mechanisms. This receptor differs from VR1 and VRL-1, which are activated by heat or chemical stimuli.
1. The primary function of thermoreceptors is:
a) Pain perception
b) Temperature detection
c) Pressure detection
d) Muscle stretch detection
Answer & Explanation:
Correct Answer: b) Temperature detection
Thermoreceptors are specialized sensory receptors that detect changes in temperature, allowing the body to maintain homeostasis. They are classified into cold and warm receptors, contributing to thermoregulation and behavioral responses to temperature changes.
2. VR1 receptor is activated by:
a) Menthol
b) Moderate cold
c) Capsaicin and high heat
d) Low pressure
Answer & Explanation:
Correct Answer: c) Capsaicin and high heat
VR1 (Vanilloid Receptor 1) is activated by capsaicin, the active component in chili peppers, and high temperatures (>43°C). It plays a key role in pain sensation and detecting harmful heat, not in sensing moderate cold.
3. CMR-1 is also known as:
a) TRPV1
b) TRPM8
c) TRPV2
d) TRPA1
Answer & Explanation:
Correct Answer: b) TRPM8
CMR-1 is also known as TRPM8 (Transient Receptor Potential Melastatin 8), activated by menthol and moderate cold temperatures (~15-30°C). It helps detect environmental cold stimuli and is important for cold sensation.
4. Which receptor does NOT respond to temperature?
a) CMR-1
b) VR1
c) VRL-1
d) Meissner corpuscle
Answer & Explanation:
Correct Answer: d) Meissner corpuscle
Meissner corpuscles are mechanoreceptors responsible for detecting light touch and texture, not temperature. Thermoreceptors like CMR-1 and VR1 detect cold and heat stimuli, respectively, and contribute to thermosensation.
5. Moderate cold is sensed at approximately:
a) 5-15°C
b) 15-30°C
c) 30-40°C
d) >40°C
Answer & Explanation:
Correct Answer: b) 15-30°C
CMR-1 (TRPM8) is activated by moderate cold in the range of 15–30°C. This range triggers appropriate physiological and behavioral responses to maintain thermal homeostasis and comfort.
6. Activation of CMR-1 leads to:
a) Pain sensation
b) Cold sensation
c) Heat sensation
d) Vibration sensation
Answer & Explanation:
Correct Answer: b) Cold sensation
Activation of CMR-1 receptors induces a cold sensation in the brain. These receptors detect cooling stimuli, enabling the body to react to environmental temperature changes and maintain internal temperature balance.
7. VRL-1 receptor is primarily activated by:
a) Moderate cold
b) High heat
c) Menthol
d) Light touch
Answer & Explanation:
Correct Answer: b) High heat
VRL-1 is primarily activated by high temperatures and plays a role in detecting noxious heat stimuli above normal body temperature. It is not involved in cold sensation.
8. Which is a chemical activator of CMR-1?
a) Capsaicin
b) Menthol
c) Bradykinin
d) Histamine
Answer & Explanation:
Correct Answer: b) Menthol
Menthol activates CMR-1 (TRPM8), simulating the sensation of cold. This chemical is often used in topical analgesics for a cooling effect and pain relief.
9. VR2 receptor primarily senses:
a) Surface temperature
b) Deep tissue temperature
c) Pain
d) Touch
Answer & Explanation:
Correct Answer: b) Deep tissue temperature
VR2 receptors are involved in sensing deep tissue temperature changes, differing from CMR-1 and VR1 that respond to surface temperature and noxious heat, respectively.
10. Clinical relevance of CMR-1:
a) Assessing pain threshold
b) Diagnosing heat stroke
c) Managing cold allodynia
d) Measuring vibration sense
Answer & Explanation:
Correct Answer: c) Managing cold allodynia
CMR-1 receptors are important in cold allodynia, where non-painful cold stimuli cause pain. Understanding its role helps in treating neuropathic conditions and developing targeted therapies to alleviate abnormal cold sensitivity.
Topic: Neuromuscular System
Subtopic: Cerebellar Function and Disorders
Keyword Definitions:
- Cerebellum: Part of the brain responsible for coordination, balance, and fine motor control.
- Dysmetria: Inability to judge distance or scale of movement.
- Hypertonia: Increased muscle tone leading to stiffness.
- Ataxia: Lack of voluntary coordination of muscle movements.
- Past-pointing: A cerebellar sign where a patient overshoots a target when attempting to touch it.
Lead Question - 2013
Cerebellar damage causes all except ? (September 2008)
a) Dysmetria
b) Hypertonia
c) Ataxia
d) Past-pointing
Answer & Explanation:
Correct Answer: b) Hypertonia
Cerebellar damage typically results in symptoms like dysmetria, ataxia, and past-pointing due to disrupted coordination and balance. However, hypertonia is not characteristic of cerebellar lesions but is more associated with upper motor neuron damage. Cerebellar dysfunction primarily causes hypotonia and impaired fine motor control.
1. Most common cause of cerebellar ataxia ?
a) Stroke
b) Peripheral neuropathy
c) Cerebellar degeneration
d) Muscle dystrophy
Answer & Explanation:
Correct Answer: c) Cerebellar degeneration
Cerebellar ataxia commonly results from cerebellar degeneration due to chronic alcoholism, genetic disorders, or paraneoplastic syndromes. It impairs coordination, balance, and fine motor control. Early recognition helps in managing symptoms and preventing complications by initiating targeted rehabilitation and therapy.
2. Dysmetria test involves:
a) Finger-to-nose test
b) Babinski reflex
c) Plantar reflex
d) Deep tendon reflex
Answer & Explanation:
Correct Answer: a) Finger-to-nose test
Dysmetria is assessed using the finger-to-nose test, where the patient’s inability to touch their nose accurately indicates cerebellar dysfunction. Overshooting or undershooting the target suggests impaired proprioception and coordination, hallmark features of cerebellar damage.
3. Ataxia affects:
a) Voluntary muscle strength
b) Coordination of movements
c) Sensory perception
d) Reflexes only
Answer & Explanation:
Correct Answer: b) Coordination of movements
Ataxia reflects impaired coordination of voluntary movements due to cerebellar dysfunction. Patients display unsteady gait, difficulty with fine motor tasks, and poor balance, but muscle strength remains generally intact. Recognizing ataxia is vital for early intervention.
4. Past-pointing indicates:
a) Involuntary muscle contraction
b) Overshooting a target
c) Loss of sensation
d) Enhanced reflexes
Answer & Explanation:
Correct Answer: b) Overshooting a target
Past-pointing is a cerebellar sign where patients overshoot the target when attempting to touch it. This demonstrates impaired proprioception and motor planning due to cerebellar dysfunction. It is assessed during coordination tests to evaluate cerebellar integrity.
5. Hypotonia in cerebellar lesions is due to:
a) Increased reflex activity
b) Loss of inhibitory control
c) Impaired motor planning
d) Decreased sensory input
Answer & Explanation:
Correct Answer: c) Impaired motor planning
Hypotonia in cerebellar lesions results from disrupted motor planning and coordination. Unlike hypertonia seen in upper motor neuron lesions, cerebellar damage leads to decreased muscle tone and poor posture control, contributing to unsteady movements and balance difficulties.
6. Common clinical feature of cerebellar lesion:
a) Muscle rigidity
b) Muscle atrophy
c) Intention tremor
d) Flaccid paralysis
Answer & Explanation:
Correct Answer: c) Intention tremor
An intention tremor is a hallmark feature of cerebellar lesions, where the tremor worsens during voluntary movement toward a target. This contrasts with resting tremors of Parkinson’s disease. It signifies defective cerebellar coordination of purposeful actions.
7. Cerebellar lesion affects which side of the body ?
a) Ipsilateral
b) Contralateral
c) Bilateral
d) Randomly
Answer & Explanation:
Correct Answer: a) Ipsilateral
Cerebellar lesions affect the ipsilateral side of the body because cerebellar pathways do not decussate. Thus, damage to the right cerebellar hemisphere results in motor deficits on the right side, an important diagnostic consideration.
8. Intention tremor is worsened during:
a) Rest
b) Voluntary movement
c) Sleep
d) Reflex action
Answer & Explanation:
Correct Answer: b) Voluntary movement
Intention tremor worsens during voluntary movement toward a target, reflecting impaired cerebellar coordination. It differentiates cerebellar from extrapyramidal tremors and helps localize neurological damage, enabling targeted therapeutic interventions.
9. Cerebellar dysfunction assessment includes:
a) MRI scan only
b) Blood tests
c) Clinical coordination tests
d) Muscle biopsy
Answer & Explanation:
Correct Answer: c) Clinical coordination tests
Assessment of cerebellar dysfunction involves clinical coordination tests like finger-to-nose and heel-to-shin tests. These reveal ataxia, dysmetria, and intention tremor, essential for diagnosis. Imaging aids in further evaluation, but clinical examination is crucial for early detection.
10. Therapeutic approach for cerebellar damage includes:
a) Antibiotics
b) Physical therapy
c) Antivirals
d) Chemotherapy
Answer & Explanation:
Correct Answer: b) Physical therapy
Physical therapy is key in managing cerebellar damage, focusing on improving coordination, balance, and muscle tone. Structured rehabilitation helps patients adapt, promoting functional independence. Early therapy initiation enhances outcomes and mitigates long-term disability.
Topic: Neuromuscular Reflexes
Subtopic: Primitive Reflexes
Keyword Definitions:
- Asymmetric Tonic Neck Reflex (ATNR): A primitive reflex in infants where turning the head causes limb extension on the same side.
- Muscle tone: The continuous and passive partial contraction of muscles.
- Primitive reflexes: Reflex actions present at birth and integrated during normal development.
Lead Question - 2013
Significance of absence of loss of asymmetric tonic neck reflex in 9 months ? (September 2008)
a) Decreased muscle tone
b) Increased muscle tone
c) Normal phenomenon
d) None of the above
Answer & Explanation:
Correct Answer: b) Increased muscle tone
Persistence of the asymmetric tonic neck reflex (ATNR) beyond 6 months, especially at 9 months, is abnormal and suggests increased muscle tone. This may indicate neurological disorders like cerebral palsy, where primitive reflexes are not properly inhibited, affecting voluntary motor control. Early detection aids in managing developmental delays.
1. ATNR normally integrates by which age ?
a) 1 month
b) 3 months
c) 6 months
d) 12 months
Answer & Explanation:
Correct Answer: c) 6 months
ATNR normally integrates by 6 months as the infant’s brain matures. Persistence beyond this age is clinically significant, often pointing to neurological disorders. Proper integration indicates healthy neurological development and progression from involuntary to voluntary motor control, essential in developmental assessment.
2. Clinical significance of persistent ATNR ?
a) Sign of neurological health
b) Normal in all infants
c) Indicator of neurological disorder
d) Sign of cardiovascular issue
Answer & Explanation:
Correct Answer: c) Indicator of neurological disorder
A persistent ATNR suggests an underlying neurological disorder, such as cerebral palsy. It reflects abnormal maturation of the central nervous system where primitive reflexes are not inhibited. This clinical sign helps early diagnosis and intervention planning to support motor and cognitive development.
3. ATNR assessment helps evaluate:
a) Respiratory function
b) Cardiovascular health
c) Neurological maturation
d) Digestive function
Answer & Explanation:
Correct Answer: c) Neurological maturation
ATNR assessment is a key indicator of neurological maturation in infants. Proper integration by 6 months signifies healthy central nervous system development, while persistence raises suspicion of disorders. Early assessment enables prompt diagnosis and intervention, supporting healthy developmental outcomes.
4. Persistence of ATNR is most commonly associated with:
a) Asthma
b) Cerebral palsy
c) Diabetes
d) Congenital heart disease
Answer & Explanation:
Correct Answer: b) Cerebral palsy
Persistent ATNR is commonly linked to cerebral palsy, reflecting improper neurological inhibition of primitive reflexes. It signals impaired central nervous system development, warranting early therapeutic intervention. Timely identification aids in managing motor dysfunction and improving patient outcomes.
5. ATNR helps in early:
a) Respiratory regulation
b) Muscle coordination
c) Digestive enzyme release
d) Hormonal balance
Answer & Explanation:
Correct Answer: b) Muscle coordination
ATNR plays a role in early muscle coordination development, aiding the infant in learning hand-eye coordination and spatial awareness. Its disappearance by 6 months marks a transition to voluntary control, crucial for further motor development and normal growth patterns.
6. Abnormal persistence of ATNR may result in:
a) Improved reflex control
b) Difficulty in voluntary movements
c) Enhanced muscle strength
d) Normal development
Answer & Explanation:
Correct Answer: b) Difficulty in voluntary movements
Persistent ATNR disrupts voluntary movement development, causing challenges in posture, coordination, and motor planning. This abnormality typically indicates neurological issues like cerebral palsy. Early detection facilitates interventions focused on improving voluntary motor control and overall functional development.
7. ATNR is also termed:
a) Symmetrical tonic neck reflex
b) Asymmetrical tonic neck reflex
c) Stretch reflex
d) Postural reflex
Answer & Explanation:
Correct Answer: b) Asymmetrical tonic neck reflex
The correct term for the tonic neck reflex is the Asymmetrical Tonic Neck Reflex (ATNR), characterized by turning the infant's head to one side, causing the ipsilateral limbs to extend and the contralateral limbs to flex. This primitive reflex is crucial for early coordination development.
8. ATNR integrates due to maturation of:
a) Spinal cord only
b) Brainstem only
c) Cerebral cortex
d) Peripheral nerves
Answer & Explanation:
Correct Answer: c) Cerebral cortex
Integration of ATNR occurs as the cerebral cortex matures, allowing voluntary motor control to override primitive reflexes. This reflects healthy neurological development, with cortical inhibition progressively replacing reflex-driven responses by around 6 months of age.
9. Clinical test for ATNR involves:
a) Stroking the sole
b) Turning the infant's head to one side
c) Pulling the infant upward
d) Stimulating the palm
Answer & Explanation:
Correct Answer: b) Turning the infant's head to one side
The clinical test for ATNR involves gently turning the infant's head to one side, eliciting extension of the ipsilateral arm and leg, and flexion of the opposite limbs. This helps assess neurological development and detect persistence indicating potential disorders.
10. Importance of assessing ATNR at 9 months is to:
a) Check muscle tone
b) Assess feeding habits
c) Evaluate neurological development
d) Check cardiovascular health
Answer & Explanation:
Correct Answer: c) Evaluate neurological development
Assessing ATNR at 9 months helps evaluate neurological development. Its persistence suggests developmental delay or neurological disorders like cerebral palsy, prompting further investigation. Timely assessment is critical for early diagnosis and therapeutic intervention, aiming to improve developmental outcomes.
Topic: Neuromuscular Reflexes
Subtopic: Primitive Reflexes
Keyword Definitions:
- Tonic neck reflex: A primitive reflex in infants causing head-turning to extend limbs on the same side.
- Disappearance Age: Age at which primitive reflexes naturally vanish during development.
- Primitive Reflexes: Reflex actions originating in the central nervous system, present at birth.
Lead Question - 2013
Tonic neck reflex disappears at what age ? (September 2008)
a) 1 month
b) 2 months
c) 3 months
d) 6 months
Answer & Explanation:
Correct Answer: c) 3 months
Tonic neck reflex typically disappears around 3 months of age as the infant's nervous system matures. Persistence beyond this age may suggest neurological abnormalities. This reflex aids early development of hand-eye coordination, but its disappearance is crucial for voluntary movement control and indicates normal neurological progression in infants.
1. What type of reflex is the tonic neck reflex ?
a) Spinal reflex
b) Primitive reflex
c) Postural reflex
d) Vestibular reflex
Answer & Explanation:
Correct Answer: b) Primitive reflex
The tonic neck reflex is classified as a primitive reflex. These reflexes are present at birth and typically disappear as the brain matures. Their presence or persistence is used as a clinical indicator of neurological development and potential abnormalities, helping clinicians assess infant development.
2. At what age do most primitive reflexes disappear ?
a) 1 month
b) 3-6 months
c) 1 year
d) 2 years
Answer & Explanation:
Correct Answer: b) 3-6 months
Primitive reflexes, including the tonic neck reflex, generally disappear by 3 to 6 months of age. This indicates proper central nervous system development. Persistent primitive reflexes beyond this window may suggest neurological disorders and require further evaluation to rule out underlying pathologies.
3. Clinical importance of disappearance of tonic neck reflex ?
a) Indicates respiratory health
b) Reflects neurological development
c) Shows gastrointestinal health
d) Indicates cardiac maturity
Answer & Explanation:
Correct Answer: b) Reflects neurological development
The disappearance of the tonic neck reflex reflects proper neurological development and maturation of the central nervous system. It signifies progression from involuntary reflexes to voluntary motor control. Persistence may indicate cerebral palsy or other neurological disorders, making it a critical assessment in pediatric exams.
4. Tonic neck reflex involves movement of:
a) Head only
b) Limbs only
c) Head and ipsilateral limbs
d) Contralateral limbs only
Answer & Explanation:
Correct Answer: c) Head and ipsilateral limbs
When the infant’s head turns to one side, the arm and leg on the same side extend while the opposite limbs flex. This helps early development of hand-eye coordination but should disappear as voluntary motor control develops to prevent abnormal persistence.
5. Persistence of tonic neck reflex beyond normal age suggests?
a) Normal variation
b) Neurological disorder
c) Cardiac anomaly
d) Respiratory infection
Answer & Explanation:
Correct Answer: b) Neurological disorder
Persistence of the tonic neck reflex beyond 3-6 months suggests a possible neurological disorder such as cerebral palsy. It indicates a delay in central nervous system maturation and warrants further clinical investigation to assess the infant’s neurological status and rule out pathological causes.
6. Which structure integrates the tonic neck reflex?
a) Cerebral cortex
b) Brainstem
c) Spinal cord
d) Cerebellum
Answer & Explanation:
Correct Answer: b) Brainstem
The brainstem serves as the integration center for the tonic neck reflex. It manages primitive reflexes by coordinating sensory input and motor responses. Proper brainstem function is crucial for reflex development and overall neurological health, making its assessment vital in pediatric examinations.
7. Tonic neck reflex is also known as:
a) Moro reflex
b) Asymmetrical tonic neck reflex (ATNR)
c) Palmar grasp reflex
d) Startle reflex
Answer & Explanation:
Correct Answer: b) Asymmetrical tonic neck reflex (ATNR)
The tonic neck reflex is specifically termed the Asymmetrical Tonic Neck Reflex (ATNR). It involves turning the infant's head to one side, causing the ipsilateral limbs to extend. It's a primitive reflex essential for early coordination but should fade with neurological maturation.
8. Clinical test for tonic neck reflex involves:
a) Stroking the sole
b) Turning the head to one side
c) Touching the palm
d) Pulling the infant upward
Answer & Explanation:
Correct Answer: b) Turning the head to one side
The clinical test for the tonic neck reflex involves gently turning the infant’s head to one side. This elicits extension of the arm and leg on the same side (ipsilateral) and flexion of the opposite limbs, assessing the reflex's presence and neurological development status.
9. Which condition is commonly associated with persistent ATNR?
a) Cerebral palsy
b) Asthma
c) Diabetes
d) Hypertension
Answer & Explanation:
Correct Answer: a) Cerebral palsy
Persistent Asymmetrical Tonic Neck Reflex (ATNR) beyond the expected developmental period is often associated with cerebral palsy. It suggests neurological impairment where primitive reflexes do not integrate properly, highlighting the need for early intervention and developmental support.
10. When does normal integration of ATNR typically occur ?
a) By 6 months
b) By 1 year
c) By 2 years
d) At birth
Answer & Explanation:
Correct Answer: a) By 6 months
Normal integration of the Asymmetrical Tonic Neck Reflex (ATNR) typically occurs by around 6 months of age. This reflects the maturation of the infant’s nervous system. If persistence is observed beyond this period, it may indicate developmental delays or neurological disorders requiring clinical attention. Topic: Sensory Pathways
Subtopic: Proprioception and Vibration Sense
Keywords:
Joint position sense: Ability to perceive the position of a joint in space.
Vibration sense: Ability to perceive oscillatory stimuli applied to the skin.
Proprioception: The body's ability to perceive its own position in space.
Aβ fibers: Large, myelinated nerve fibers that transmit proprioceptive and vibration information.
Lead Question - 2013 (September 2008)
Joint position & vibration sense is carried by?
a) Act
b) A(3)
c) Aβ
d) B
Answer: c) Aβ
Explanation: Joint position and vibration sense are carried by Aβ fibers, which are large, myelinated fibers. These fibers are responsible for transmitting proprioceptive and fine touch information rapidly to the central nervous system, particularly important for balance and coordinated movements.
1. Which tract primarily carries joint position and vibration sense to the brain?
a) Corticospinal tract
b) Spinothalamic tract
c) Dorsal column-medial lemniscus pathway
d) Spinocerebellar tract
Answer: c) Dorsal column-medial lemniscus pathway
Explanation: The dorsal column-medial lemniscus pathway transmits fine touch, vibration, and proprioceptive information from the periphery to the cerebral cortex. Aβ fibers synapse in the dorsal column nuclei, ascend, and cross in the medulla before reaching the thalamus and cortex.
2. Damage to Aβ fibers results in?
a) Loss of pain sensation
b) Loss of joint position and vibration sense
c) Loss of temperature sensation
d) Loss of motor function
Answer: b) Loss of joint position and vibration sense
Explanation: Aβ fiber damage disrupts the transmission of joint position and vibration sense, leading to impaired proprioception and balance. Clinically, patients may present with ataxia, especially when visual input is removed (positive Romberg sign).
3. The proprioceptive signals are integrated primarily in which brain region?
a) Cerebellum
b) Hippocampus
c) Prefrontal cortex
d) Thalamus
Answer: a) Cerebellum
Explanation: The cerebellum integrates proprioceptive signals for coordination of movement and balance. Inputs from muscle spindles and joint receptors travel via the dorsal column and spinocerebellar tracts to the cerebellum for fine-tuning motor activity.
4. Clinical test for vibration sense involves?
a) Pinprick test
b) Tuning fork application
c) Light touch with cotton
d) Reflex hammer percussion
Answer: b) Tuning fork application
Explanation: The tuning fork is applied over bony prominences to assess vibration sense. Reduced or absent vibration sense suggests a defect in large myelinated fibers (Aβ) or dorsal column pathology, as seen in conditions like tabes dorsalis.
5. Joint position sense is most impaired in:
a) Peripheral neuropathy
b) Alzheimer’s disease
c) Migraine
d) Bell's palsy
Answer: a) Peripheral neuropathy
Explanation: Peripheral neuropathy damages large myelinated fibers (Aβ), impairing proprioceptive signals and resulting in unsteady gait and balance problems. Patients may show positive Romberg sign, particularly when deprived of visual input.
6. The dorsal column is composed of:
a) Fasciculus gracilis and fasciculus cuneatus
b) Spinothalamic and spinocerebellar tracts
c) Corticospinal and rubrospinal tracts
d) Medial lemniscus only
Answer: a) Fasciculus gracilis and fasciculus cuneatus
Explanation: The dorsal column consists of fasciculus gracilis (lower body) and fasciculus cuneatus (upper body). They transmit fine touch, vibration, and proprioceptive information via Aβ fibers to the brain.
7. Romberg's test evaluates:
a) Muscle strength
b) Proprioceptive function
c) Pain sensation
d) Visual acuity
Answer: b) Proprioceptive function
Explanation: Romberg's test assesses proprioceptive function. A positive Romberg sign indicates impaired joint position sense or dorsal column dysfunction, causing instability when eyes are closed.
8. Vibration sense testing is best done over:
a) Soft tissue
b) Bony prominences
c) Skin surface
d) Muscle belly
Answer: b) Bony prominences
Explanation: Bony prominences are ideal for vibration sense testing because they transmit vibrations better. Tuning fork application on these areas assesses Aβ fiber function and dorsal column integrity.
9. Proprioceptive deficit presents as:
a) Muscle weakness
b) Ataxia
c) Hyperreflexia
d) Tremors
Answer: b) Ataxia
Explanation: Loss of proprioception leads to ataxia, characterized by uncoordinated movements, especially evident when visual input is removed. This occurs due to impaired joint position and vibration sense carried by Aβ fibers.
10. Which sensory fiber type carries touch, pressure, and proprioception?
a) Aα
b) Aβ
c) Aδ
d) C fibers
Answer: b) Aβ
Explanation: Aβ fibers are large, myelinated fibers responsible for transmitting touch, pressure, proprioceptive, and vibration sensations rapidly to the central nervous system, ensuring precise perception of body position and movement.
Chapter: Central Nervous System
Topic: Limbic System
Subtopic: Papez Circuit
Keywords:
Papez Circuit: Neural circuit involved in controlling emotional expression.
Nucleus: Collection of neurons in the central nervous system responsible for specific functions.
Thalamus: Part of the brain that relays motor and sensory signals to the cerebral cortex.
Anterior Nucleus of Thalamus: Thalamic nucleus involved in memory and part of the limbic system.
Lead Question - 2013
The nucleus involved in Papez circuit is:
a) Pulvinar
b) Intralaminar
c) VPL nucleus
d) Anterior nucleus of Thalamus
Answer: d) Anterior nucleus of Thalamus
Explanation: The anterior nucleus of the thalamus plays a key role in the Papez circuit, which is critical for regulating emotions and memory. It receives input from the mammillary bodies via the mammillothalamic tract and projects to the cingulate cortex, forming an essential part of this limbic pathway.
1. Which of the following is not part of the Papez circuit?
a) Hippocampus
b) Anterior nucleus of thalamus
c) Cerebellum
d) Cingulate gyrus
Answer: c) Cerebellum
Explanation: The cerebellum is not part of the Papez circuit. The circuit includes the hippocampus, anterior nucleus of the thalamus, mammillary bodies, cingulate gyrus, and entorhinal cortex, and plays a major role in processing emotions and memory functions.
2. Lesion in the anterior nucleus of the thalamus can cause:
a) Ataxia
b) Korsakoff’s syndrome
c) Hemiplegia
d) Aphasia
Answer: b) Korsakoff’s syndrome
Explanation: Damage to the anterior nucleus of the thalamus, as seen in Korsakoff’s syndrome, disrupts memory formation and leads to confabulation and memory loss. It is commonly associated with chronic alcoholism and thiamine deficiency affecting the limbic system.
3. The Papez circuit is primarily associated with:
a) Motor coordination
b) Emotional regulation
c) Language processing
d) Visual perception
Answer: b) Emotional regulation
Explanation: The Papez circuit, consisting of interconnected brain regions such as the hippocampus, anterior thalamic nuclei, and cingulate gyrus, plays a critical role in regulating emotions and memory processes, making it essential in the limbic system’s function.
4. The mammillothalamic tract connects:
a) Mammillary body to anterior nucleus of thalamus
b) Hippocampus to cingulate gyrus
c) Pulvinar to entorhinal cortex
d) Amygdala to hypothalamus
Answer: a) Mammillary body to anterior nucleus of thalamus
Explanation: The mammillothalamic tract connects the mammillary body to the anterior nucleus of the thalamus. It plays a crucial role in the Papez circuit by relaying information essential for emotional and memory processing within the limbic system.
5. Clinical dysfunction in the Papez circuit primarily results in:
a) Ataxia
b) Memory impairment
c) Aphasia
d) Seizures
Answer: b) Memory impairment
Explanation: Dysfunction in the Papez circuit, such as lesions affecting the anterior nucleus of the thalamus or hippocampus, leads to memory deficits. This occurs because the circuit is central to memory consolidation and emotional regulation, linking various structures in the limbic system.
6. The Papez circuit connects to the cerebral cortex via:
a) Internal capsule
b) Fornix
c) Corpus callosum
d) Mammillary body
Answer: b) Fornix
Explanation: The fornix is the major fiber tract connecting the hippocampus to the mammillary bodies, which further projects to the anterior nucleus of the thalamus. This anatomical pathway is a crucial component of the Papez circuit, essential for memory and emotion processing.
7. Damage to the anterior nucleus of the thalamus results in?
a) Wernicke's aphasia
b) Korsakoff’s psychosis
c) Huntington's chorea
d) Parkinson's disease
Answer: b) Korsakoff’s psychosis
Explanation: The anterior nucleus of the thalamus is a critical relay in the Papez circuit. Its damage leads to Korsakoff’s psychosis, characterized by severe memory loss, confabulation, and learning difficulties. This is commonly associated with thiamine deficiency in chronic alcoholics.
8. Anterior nucleus of thalamus is part of which brain system?
a) Reticular formation
b) Limbic system
c) Basal ganglia
d) Extrapyramidal system
Answer: b) Limbic system
Explanation: The anterior nucleus of the thalamus is part of the limbic system, which is involved in emotion regulation, memory formation, and integration of autonomic responses. It acts as a relay between the mammillary bodies and cingulate gyrus.
9. Which structure does not participate in the Papez circuit?
a) Hippocampus
b) Amygdala
c) Cingulate gyrus
d) Anterior nucleus of thalamus
Answer: b) Amygdala
Explanation: The amygdala, although involved in emotion processing, is not a component of the Papez circuit. The circuit primarily involves the hippocampus, anterior nucleus of the thalamus, mammillary bodies, and cingulate gyrus.
10. Damage to the Papez circuit most likely leads to:
a) Visual disturbances
b) Severe memory impairment
c) Motor weakness
d) Loss of smell
Answer: b) Severe memory impairment
Explanation: The Papez circuit is integral for memory consolidation and emotional processing. Damage, particularly to the anterior nucleus of the thalamus or hippocampus, impairs memory formation, leading to conditions like amnesia and confabulation, especially seen in Korsakoff’s syndrome.
Topic: Reflexes
Subtopic: Righting Reflex
Righting Reflex: Reflex that helps maintain normal posture.
Postural Reflex: Reflex that helps maintain body posture against gravity.
Stretch Reflex: Reflex in response to muscle stretching.
Spinal Reflex: Reflex controlled by spinal cord without brain involvement.
Ocular Reflex: Reflex related to eye movements.
Lead Question - 2013
Righting reflex is a ? (September 2008)
a) Stretch reflex
b) Postural reflex
c) Spinal reflex
d) Ocular reflex
Explanation: The righting reflex is a postural reflex that helps maintain body posture and balance by repositioning the head and body when they are displaced. It is primarily mediated through the vestibular system and helps in stabilizing the body against gravity. The correct answer is (b) Postural reflex.
Which of the following reflexes helps maintain posture against gravity?
a) Stretch reflex
b) Postural reflex
c) Ocular reflex
d) Gag reflex
Explanation: Postural reflex helps in maintaining body posture and balance by adjusting the body position relative to gravity. This reflex is vital for standing and walking. It primarily involves signals from the vestibular system and proprioceptors. The correct answer is (b) Postural reflex.
What type of reflex is mediated without brain involvement?
a) Ocular reflex
b) Postural reflex
c) Spinal reflex
d) Righting reflex
Explanation: A spinal reflex is mediated by the spinal cord without brain involvement, allowing for quick responses to stimuli, such as the knee-jerk reaction. This enables immediate reaction to maintain posture and protect the body. The correct answer is (c) Spinal reflex.
Damage to which system impairs righting reflex?
a) Cochlear system
b) Vestibular system
c) Visual system
d) Motor cortex
Explanation: The vestibular system provides essential sensory input for the righting reflex, helping the body maintain equilibrium. Damage to this system can impair the righting reflex, leading to balance problems and falls. The correct answer is (b) Vestibular system.
Which reflex corrects the position of the head in space?
a) Stretch reflex
b) Ocular reflex
c) Righting reflex
d) Flexor reflex
Explanation: The righting reflex helps correct the position of the head and body in space, ensuring proper posture and balance by detecting deviations from the upright position. It primarily involves vestibular input. The correct answer is (c) Righting reflex.
Righting reflex is essential for patients recovering from:
a) Stroke
b) Cochlear damage
c) Myocardial infarction
d) Asthma
Explanation: In stroke patients, the righting reflex may be impaired due to damage to the vestibular or central nervous systems, leading to poor balance and posture. Rehabilitation focuses on restoring this reflex to improve functional recovery. The correct answer is (a) Stroke.
Which nucleus integrates the righting reflex?
a) Suprachiasmatic nucleus
b) Vestibular nucleus
c) Preoptic nucleus
d) Paraventricular nucleus
Explanation: The vestibular nucleus integrates sensory inputs from the vestibular apparatus and coordinates the righting reflex. It helps maintain posture and equilibrium by processing signals related to head and body position. The correct answer is (b) Vestibular nucleus.
Clinical implication of impaired righting reflex includes:
a) Hypotension
b) Ataxia
c) Bradycardia
d) Anemia
Explanation: Ataxia refers to lack of coordination in movement due to impaired righting reflex. This can result from vestibular damage or neurological disorders, causing difficulty in maintaining balance and posture. The correct answer is (b) Ataxia.
Primary sensory input for righting reflex comes from:
a) Cochlea
b) Muscle spindles
c) Vestibular apparatus
d) Retina
Explanation: The primary sensory input for the righting reflex is from the vestibular apparatus, which detects changes in head position and motion, providing critical information to maintain balance and posture. The correct answer is (c) Vestibular apparatus.
Righting reflex is impaired in which condition?
a) Meniere's disease
b) Myocardial infarction
c) Diabetes mellitus
d) Hypertension
Explanation: Meniere's disease affects the inner ear and impairs the vestibular system, leading to impaired righting reflex, dizziness, and balance disturbances. The correct answer is (a) Meniere's disease.
Righting reflex is classified as:
a) Simple reflex
b) Spinal reflex
c) Postural reflex
d) Autonomic reflex
Explanation: The righting reflex is classified as a postural reflex because it helps maintain body posture and balance by detecting deviations from the upright position. The correct answer is (c) Postural reflex.
Topic: Reflex Arcs
Subtopic: Righting Reflex
Righting reflex: Reflex that helps maintain upright posture by correcting body position automatically in response to sensory inputs.
Cochlear reflex: Reflex related to auditory function, not involved in body posture control.
Spinal reflex: Simple reflexes mediated by the spinal cord, not involving higher centers like the midbrain for complex posture control.
Vestibular reflex: Reflex originating from the vestibular system in the inner ear, critical for maintaining balance and posture.
Lead Question - 2013 (September 2008)
Righting reflex is a ?
a) Cochlear reflex
b) Spinal reflex
c) Vestibular reflex
d) None of the above
Answer: c) Vestibular reflex
Explanation: The righting reflex is a vestibular reflex that helps maintain body posture by processing vestibular input from the inner ear in the midbrain. It automatically adjusts the body and head position in response to changes in orientation, preventing falls and aiding balance during movements.
1. Guessed Question
The primary sensory organ involved in righting reflex is:
a) Retina
b) Cochlea
c) Vestibular apparatus
d) Olfactory bulb
Answer: c) Vestibular apparatus
Explanation: The vestibular apparatus in the inner ear detects changes in head position and motion. It sends signals to the midbrain to adjust body posture via the righting reflex, maintaining balance and preventing falls automatically.
2. Guessed Question
Loss of righting reflex suggests lesion in:
a) Cerebellum
b) Vestibular pathways
c) Auditory nerve
d) Olfactory nerve
Answer: b) Vestibular pathways
Explanation: Lesions in the vestibular pathways, including the vestibular nerve or midbrain centers, impair the righting reflex. This prevents proper integration of sensory inputs needed for maintaining posture, resulting in imbalance and a tendency to fall.
3. Guessed Question
Which brain structure integrates the righting reflex?
a) Medulla
b) Midbrain
c) Pons
d) Spinal cord
Answer: b) Midbrain
Explanation: The midbrain integrates inputs from the vestibular apparatus and visual system to control the righting reflex. It rapidly adjusts postural muscle tone and body orientation without conscious effort, ensuring balance during movements or displacement.
4. Guessed Question
Righting reflex mainly helps in:
a) Hearing improvement
b) Postural correction
c) Voluntary limb movement
d) Respiratory rate regulation
Answer: b) Postural correction
Explanation: The righting reflex automatically adjusts head and body position in space by processing vestibular inputs. It helps prevent falls and maintain an upright posture, acting without conscious control, essential for normal daily activities and movement stability.
5. Guessed Question
Clinical test of righting reflex is useful to assess:
a) Liver function
b) Vestibular integrity
c) Visual acuity
d) Motor strength
Answer: b) Vestibular integrity
Explanation: Testing the righting reflex clinically helps assess the integrity of vestibular pathways. Impairment in the reflex suggests damage in the vestibular system or midbrain, indicating balance disorders or neurological deficits, aiding diagnosis and treatment planning.
6. Guessed Question
Righting reflex is important for:
a) Digestive enzyme release
b) Conscious decision-making
c) Maintaining upright posture
d) Hormonal regulation
Answer: c) Maintaining upright posture
Explanation: The righting reflex ensures automatic maintenance of upright posture. It quickly compensates for head and body displacement using midbrain integration of sensory inputs, enabling balance without voluntary effort or conscious awareness, essential for everyday stability.
7. Guessed Question
The righting reflex adjusts:
a) Limb length
b) Muscle tone
c) Hair growth
d) Joint structure
Answer: b) Muscle tone
Explanation: The righting reflex adjusts muscle tone in response to vestibular inputs, allowing rapid postural corrections. This ensures head and body alignment during changes in position, preventing falls and providing stability during voluntary and involuntary movements.
8. Guessed Question
Which reflex is NOT related to posture control?
a) Righting reflex
b) Vestibulospinal reflex
c) Patellar reflex
d) Labyrinthine reflex
Answer: c) Patellar reflex
Explanation: The patellar reflex is a simple spinal reflex that regulates knee extension in response to muscle stretch. It is not directly involved in posture control like the righting, vestibulospinal, or labyrinthine reflexes, which maintain body orientation and balance automatically.
9. Guessed Question
Righting reflex failure is commonly seen in:
a) Vestibular neuronitis
b) Diabetes mellitus
c) Hypertension
d) Migraine
Answer: a) Vestibular neuronitis
Explanation: Vestibular neuronitis causes inflammation of the vestibular nerve, impairing the righting reflex. This results in severe imbalance and vertigo, demonstrating the essential role of the vestibular system and midbrain in postural control and automatic body orientation adjustments.
Topic: Reflex Arcs
Subtopic: Righting Reflex
Righting reflex: Reflex that helps maintain upright posture by correcting body position.
Pons: Part of the brainstem involved in motor control and sensory analysis but not primary for righting reflex.
Spinal cord: Facilitates simple reflexes but higher centers are involved in complex postural reflexes.
Cortex: Controls voluntary movements but not responsible for reflex integration.
Midbrain: Higher center integrating vestibular inputs, critical for righting reflex and posture control.
Lead Question - 2013 (September 2008)
Higher center for righting reflex?
a) Pons
b) Spinal cord
c) Cortex
d) Midbrain
Answer: d) Midbrain
Explanation: The midbrain acts as the higher center for the righting reflex, integrating vestibular and visual inputs to help maintain posture and correct body position after displacement. This reflex helps in stabilizing the head and body in space, maintaining upright posture without conscious effort.
1. Guessed Question
Righting reflex primarily helps in:
a) Regulating heart rate
b) Maintaining upright posture
c) Digestive motility
d) Hormone secretion
Answer: b) Maintaining upright posture
Explanation: The righting reflex is crucial for maintaining upright posture. It corrects head and body orientation automatically through midbrain processing of sensory inputs. This ensures balance during movement and prevents falls, especially in response to sudden shifts in body position.
2. Guessed Question
The righting reflex is mediated by which sensory input?
a) Auditory
b) Vestibular
c) Olfactory
d) Gustatory
Answer: b) Vestibular
Explanation: Vestibular input from the inner ear provides critical information for the righting reflex. The midbrain processes this input to adjust body and head posture, enabling automatic correction of balance when the body is displaced, preventing instability or falls.
3. Guessed Question
Lesion of the midbrain would impair:
a) Pain sensation
b) Righting reflex
c) Voluntary speech
d) Visual acuity
Answer: b) Righting reflex
Explanation: A lesion in the midbrain disrupts the righting reflex by impairing integration of vestibular and visual inputs necessary for postural correction. This leads to inability to maintain upright posture, resulting in imbalance, falls, and coordination difficulties.
4. Guessed Question
Which of the following is NOT involved in righting reflex?
a) Midbrain
b) Vestibular apparatus
c) Auditory cortex
d) Visual system
Answer: c) Auditory cortex
Explanation: The auditory cortex is unrelated to the righting reflex. The midbrain integrates vestibular and visual inputs to correct posture and maintain balance. Auditory pathways do not contribute to this reflex, which is crucial for body orientation and stability.
5. Guessed Question
Righting reflex becomes prominent at what stage of development?
a) Adulthood
b) Neonatal period
c) Infancy
d) Old age
Answer: c) Infancy
Explanation: The righting reflex is most prominent in infancy when postural control is immature. It allows the infant to correct body position in response to head displacement automatically. As voluntary motor control develops, reliance on the reflex decreases, indicating normal neurological development.
6. Guessed Question
The righting reflex primarily prevents:
a) Seizures
b) Falls
c) Headaches
d) Muscle atrophy
Answer: b) Falls
Explanation: The righting reflex prevents falls by automatically adjusting body posture in response to changes in head or body position. Vestibular inputs to the midbrain trigger compensatory muscle tone adjustments, ensuring stability without conscious effort.
7. Guessed Question
Damage to which structure leads to loss of righting reflex?
a) Cerebellum
b) Medulla
c) Midbrain
d) Thalamus
Answer: c) Midbrain
Explanation: The midbrain is the primary integration center for the righting reflex. Damage to the midbrain disrupts its ability to process vestibular and visual signals required to adjust posture automatically, leading to impaired balance and loss of the righting reflex.
8. Guessed Question
Righting reflex adjusts muscle tone via:
a) Corticospinal tract
b) Vestibulospinal tract
c) Spinothalamic tract
d) Rubrospinal tract
Answer: b) Vestibulospinal tract
Explanation: The vestibulospinal tract conveys signals from the vestibular apparatus to spinal motor neurons, adjusting muscle tone automatically as part of the righting reflex. This enables rapid postural corrections without cortical involvement, ensuring balance during dynamic body movements.
9. Guessed Question
Which clinical condition may show loss of righting reflex?
a) Parkinson's disease
b) Vestibular neuronitis
c) Alzheimer's disease
d) Migraine
Answer: b) Vestibular neuronitis
Explanation: Vestibular neuronitis causes inflammation of the vestibular nerve, impairing sensory input to the midbrain. This leads to loss of the righting reflex, resulting in severe imbalance and dizziness. It exemplifies the crucial role of vestibular pathways in maintaining postural stability automatically.
Topic: Reflex Arcs
Subtopic: Tonic Labyrinthine Reflex
Tonic labyrinthine reflex: A primitive reflex involving body posture regulation through vestibular inputs.
Integration center: Neural structure where sensory inputs are processed to generate reflex motor output.
Spinal cord: Part of the CNS transmitting neural signals but not the main integrator for tonic labyrinthine reflex.
Medulla: Brainstem structure involved in autonomic and reflexive functions but not primary for this reflex.
Midbrain: Part of brainstem integrating vestibular signals, crucial for postural reflex control.
Cerebral cortex: Higher brain area responsible for voluntary motor control, not reflex integration.
Lead Question - 2013 (September 2008)
Integration center of tonic labyrinthine reflex is?
a) Spinal cord
b) Medulla
c) Midbrain
d) Cerebral cortex
Answer: c) Midbrain
Explanation: The tonic labyrinthine reflex integrates at the midbrain level, where vestibular inputs about head position influence postural muscle tone. It helps maintain balance by adjusting limb muscle tone in response to head movements. The spinal cord and cortex play roles in other reflexes and voluntary actions, respectively.
1. Guessed Question
Which structure integrates the tonic labyrinthine reflex?
a) Cerebellum
b) Midbrain
c) Spinal cord
d) Thalamus
Answer: b) Midbrain
Explanation: The midbrain serves as the primary integration center for the tonic labyrinthine reflex. It processes vestibular inputs from the inner ear, influencing posture and muscle tone. This reflex is vital for maintaining balance during head position changes, distinguishing it from higher cortical or spinal reflexes.
2. Guessed Question
The tonic labyrinthine reflex helps in maintaining?
a) Digestive function
b) Posture and balance
c) Cognitive function
d) Visual processing
Answer: b) Posture and balance
Explanation: The tonic labyrinthine reflex stabilizes posture by adjusting muscle tone in response to head movements, mediated by the midbrain. This reflex helps maintain equilibrium during activities like standing or walking and is especially prominent in infants before voluntary postural control matures.
3. Guessed Question
Which sensory input primarily activates the tonic labyrinthine reflex?
a) Visual input
b) Proprioceptive input
c) Vestibular input
d) Auditory input
Answer: c) Vestibular input
Explanation: Vestibular inputs from the inner ear are crucial for the tonic labyrinthine reflex. These inputs inform the midbrain about head position changes, prompting automatic adjustments in muscle tone and posture to maintain balance and equilibrium, essential for upright stance and coordinated movement.
4. Guessed Question
The tonic labyrinthine reflex is most prominent in:
a) Elderly adults
b) Healthy adults
c) Infants
d) Athletes
Answer: c) Infants
Explanation: In infants, the tonic labyrinthine reflex is dominant, aiding in early postural control before higher cortical mechanisms develop. It disappears with maturation as voluntary control takes over. Persistence of this reflex in adults may indicate neurological dysfunction.
5. Guessed Question
The primary role of the midbrain in reflexes is:
a) Memory processing
b) Visual perception
c) Integration of vestibular reflexes
d) Hormone secretion
Answer: c) Integration of vestibular reflexes
Explanation: The midbrain integrates vestibular reflexes, including the tonic labyrinthine reflex. It processes head movement and position data to maintain muscle tone and posture. This ensures equilibrium and coordinated movement during head position changes, without needing cortical input or conscious awareness.
6. Guessed Question
Lesion in the midbrain may result in disruption of:
a) Voluntary movement
b) Tonic labyrinthine reflex
c) Hormone secretion
d) Sensory perception
Answer: b) Tonic labyrinthine reflex
Explanation: Damage to the midbrain impairs integration of the tonic labyrinthine reflex, leading to postural instability and abnormal muscle tone. This results in poor balance and coordination, indicating the critical role of the midbrain in automatic postural adjustments driven by vestibular input.
7. Guessed Question
The tonic labyrinthine reflex adjusts muscle tone in response to?
a) Muscle fatigue
b) Head position changes
c) Visual stimuli
d) Pain sensation
Answer: b) Head position changes
Explanation: The tonic labyrinthine reflex modifies muscle tone in response to changes in head position. The midbrain processes vestibular input from the inner ear, regulating limb and axial muscle tone to maintain body balance and upright posture, especially during movements like tilting the head.
8. Guessed Question
Failure of the tonic labyrinthine reflex leads to:
a) Improved posture
b) Loss of equilibrium
c) Enhanced reflexes
d) Increased muscle strength
Answer: b) Loss of equilibrium
Explanation: Dysfunction in the tonic labyrinthine reflex disrupts posture regulation, leading to balance issues and potential falls. The reflex is critical for adjusting muscle tone in response to vestibular input. Its impairment suggests midbrain or vestibular system pathology, often seen in neurological disorders.
9. Guessed Question
Which pathway transmits signals for the tonic labyrinthine reflex?
a) Corticospinal tract
b) Vestibulospinal tract
c) Spinothalamic tract
d) Dorsal column
Answer: b) Vestibulospinal tract
Explanation: The vestibulospinal tract conveys signals from the vestibular apparatus to the spinal cord to modulate muscle tone and posture as part of the tonic labyrinthine reflex. This pathway bypasses higher cortical centers, enabling rapid reflexive responses to maintain equilibrium.
Topic: Reflex Arcs
Subtopic: Sensory Nerve Fibers
Stretch Impulse: Signals generated from muscle spindles in response to stretch.
Ia Fibers: Large-diameter, myelinated fibers transmitting stretch signals to the spinal cord.
Ib Fibers: Sensory fibers from Golgi tendon organs sensing tension in tendons.
B Fibers: Myelinated fibers transmitting autonomic preganglionic impulses.
C Fibers: Unmyelinated fibers carrying pain and temperature signals at slow conduction velocity.
Lead Question - 2013 (September 2008)
Stretch impulse is carried by?
a) Ia
b) Ib
c) B
d) C
Answer: a) Ia
Explanation: Stretch impulses generated by muscle spindle receptors are transmitted to the spinal cord via large-diameter myelinated Ia afferent fibers. These fibers are highly sensitive to muscle length changes and conduction is rapid, facilitating immediate reflex responses such as the stretch reflex to maintain muscle tone and posture.
1. Guessed Question
Which sensory fiber carries Golgi tendon organ signals?
a) Ia
b) Ib
c) B
d) C
Answer: b) Ib
Explanation: The Golgi tendon organ senses tension in the tendon during muscle contraction and sends impulses via Ib afferent fibers. These myelinated fibers conduct signals rapidly to the spinal cord, contributing to the autogenic inhibition reflex that prevents excessive force and protects muscles from injury.
2. Guessed Question
Which fiber type is unmyelinated and transmits pain?
a) Ia
b) Ib
c) B
d) C
Answer: d) C
Explanation: C fibers are unmyelinated sensory fibers responsible for transmitting dull, aching pain and temperature sensations. Their slow conduction velocity ensures prolonged pain sensation. They are crucial in chronic pain and inflammatory responses, contributing to body’s protective mechanisms and nociceptive signaling.
3. Guessed Question
B fibers are involved in carrying impulses to?
a) Skeletal muscle
b) Autonomic ganglia
c) Sensory cortex
d) Spinal cord
Answer: b) Autonomic ganglia
Explanation: B fibers are lightly myelinated fibers that transmit preganglionic autonomic signals from the central nervous system to autonomic ganglia. These fibers conduct impulses moderately fast, participating in autonomic regulation of visceral organs, such as heart rate, digestion, and glandular secretion.
4. Guessed Question
Muscle spindle stretch reflex helps maintain?
a) Blood pressure
b) Body temperature
c) Muscle tone and posture
d) Respiratory rate
Answer: c) Muscle tone and posture
Explanation: The stretch reflex, mediated by Ia afferent fibers from muscle spindles, plays a critical role in maintaining muscle tone and body posture. Stretch of the muscle activates spindle receptors, producing reflex contraction that stabilizes joints, preventing falls or injury during movement.
5. Guessed Question
Which receptor is primarily responsible for detecting muscle length?
a) Golgi tendon organ
b) Muscle spindle
c) Free nerve endings
d) Ruffini endings
Answer: b) Muscle spindle
Explanation: Muscle spindles are specialized stretch receptors located within skeletal muscles. They detect changes in muscle length and velocity of stretch, sending impulses through Ia afferent fibers to the spinal cord. This feedback maintains muscle tone and coordinates smooth voluntary movements.
6. Guessed Question
Ib afferent fibers regulate which reflex?
a) Stretch reflex
b) Flexor withdrawal reflex
c) Autogenic inhibition reflex
d) Crossed extensor reflex
Answer: c) Autogenic inhibition reflex
Explanation: The autogenic inhibition reflex prevents excessive muscle tension. Ib afferent fibers from Golgi tendon organs sense high tension and inhibit alpha motor neurons, reducing muscle contraction force. This protects muscles and tendons from damage during intense contraction or load lifting.
7. Guessed Question
Primary role of Ia afferent fibers in reflex arc?
a) Transmit pain
b) Transmit temperature
c) Conduct stretch information
d) Relay visual signals
Answer: c) Conduct stretch information
Explanation: Ia afferent fibers conduct stretch information from muscle spindles to the spinal cord. They are crucial in the monosynaptic stretch reflex, where muscle stretch leads to reflex contraction, maintaining posture and muscle tone. Their high conduction velocity enables rapid responses essential for movement control.
8. Guessed Question
Ib fibers originate from which organ?
a) Muscle spindle
b) Golgi tendon organ
c) Pacinian corpuscle
d) Meissner's corpuscle
Answer: b) Golgi tendon organ
Explanation: Ib fibers originate from Golgi tendon organs located at muscle-tendon junctions. They detect changes in muscle tension and relay this information to the spinal cord, playing a protective role by inhibiting excessive contraction and preventing tendon rupture during high-load activities.
9. Guessed Question
Which fibers have the fastest conduction velocity?
a) C fibers
b) B fibers
c) Ib fibers
d) Ia fibers
Answer: d) Ia fibers
Explanation: Ia fibers possess the fastest conduction velocity due to large diameter and heavy myelination. This facilitates rapid transmission of stretch impulses, essential for immediate reflex responses like the stretch reflex, contributing to quick adjustments in muscle activity and joint stability.
Topic: Neuroanatomy
Subtopic: Development of Brain Structures
Keywords:
Medulla Oblongata: The lower portion of the brainstem, responsible for autonomic functions such as breathing, heart rate, and reflex actions.
Prosencephalon: The embryonic forebrain, which develops into the cerebral hemispheres and diencephalon.
Rhombencephalon: The embryonic hindbrain, which gives rise to the pons, cerebellum, and medulla oblongata.
Mesencephalon: The embryonic midbrain, involved in motor movement and auditory/visual processing.
Lead Question - 2013:
Medulla oblongata arises from?
a) Prosencephalon
b) Rhombencephalon
c) Mesencephalon
d) None
Answer & Explanation:
Correct answer: b) Rhombencephalon.
Explanation: The medulla oblongata is derived from the embryonic rhombencephalon (hindbrain). It regulates vital autonomic functions such as breathing, heart rate, and reflexes like coughing and vomiting. Understanding its developmental origin helps in diagnosing congenital malformations and understanding brainstem pathologies.
MCQ 1:
Which part of the brainstem is directly continuous with the spinal cord?
a) Midbrain
b) Pons
c) Medulla oblongata
d) Thalamus
Answer & Explanation:
Correct answer: c) Medulla oblongata.
Explanation: The medulla oblongata forms the lowest part of the brainstem and directly continues with the spinal cord. It houses vital autonomic centers that regulate heart rate, respiration, and reflexes, making it essential for life-sustaining functions.
MCQ 2:
The medulla oblongata contains which important center?
a) Visual center
b) Respiratory center
c) Auditory center
d) Olfactory center
Answer & Explanation:
Correct answer: b) Respiratory center.
Explanation: The medulla oblongata contains the respiratory center, which controls the rate and depth of breathing. It responds to chemical and neural signals, ensuring homeostasis of blood gases, and is critical in cases of respiratory dysfunction or brainstem injury.
MCQ 3 (Clinical):
Medullary syndrome (Wallenberg syndrome) is caused by occlusion of?
a) Anterior spinal artery
b) Posterior inferior cerebellar artery (PICA)
c) Middle cerebral artery
d) Basilar artery
Answer & Explanation:
Correct answer: b) Posterior inferior cerebellar artery (PICA).
Explanation: Wallenberg syndrome occurs due to PICA occlusion, causing ipsilateral loss of pain and temperature in the face, contralateral body loss, vertigo, ataxia, and dysphagia. It highlights the medulla’s role in sensory pathways and autonomic functions.
MCQ 4:
Which cranial nerve nuclei are located in the medulla oblongata?
a) CN III, IV
b) CN V, VI
c) CN IX, X, XII
d) CN II, III
Answer & Explanation:
Correct answer: c) CN IX, X, XII.
Explanation: The medulla oblongata houses the nuclei of cranial nerves IX (Glossopharyngeal), X (Vagus), and XII (Hypoglossal), which control swallowing, cardiovascular function, and tongue movements. Damage leads to dysphagia, hoarseness, and tongue deviation.
MCQ 5 (Clinical):
A lesion in the medulla oblongata can cause?
a) Hemiplegia
b) Loss of proprioception
c) Respiratory failure
d) All of the above
Answer & Explanation:
Correct answer: d) All of the above.
Explanation: Medullary lesions can affect pyramidal tracts (causing hemiplegia), sensory pathways (causing proprioceptive loss), and the respiratory center, leading to life-threatening respiratory failure. Comprehensive assessment is vital in brainstem strokes or trauma.
MCQ 6:
The pyramidal decussation is located at?
a) Midbrain
b) Pons
c) Medulla oblongata
d) Cerebellum
Answer & Explanation:
Correct answer: c) Medulla oblongata.
Explanation: The pyramidal decussation occurs in the medulla oblongata, where most corticospinal fibers cross to the contralateral side. This explains why the left cerebral hemisphere controls the right body side, a fundamental concept in neuroanatomy and clinical neurology.
MCQ 7 (Clinical):
Which syndrome is caused by medullary infarction?
a) Horner's syndrome
b) Locked-in syndrome
c) Weber syndrome
d) Wallenberg syndrome
Answer & Explanation:
Correct answer: d) Wallenberg syndrome.
Explanation: Medullary infarction, specifically of the lateral medulla due to PICA occlusion, causes Wallenberg syndrome with symptoms like vertigo, dysphagia, and sensory deficits. Timely identification prevents long-term complications and guides treatment.
MCQ 8:
The area postrema located in the medulla oblongata is responsible for?
a) Respiratory control
b) Vomiting reflex
c) Temperature regulation
d) Sleep cycle
Answer & Explanation:
Correct answer: b) Vomiting reflex.
Explanation: The area postrema, located in the medulla oblongata, detects toxins in the blood and triggers the vomiting reflex. It lacks a blood-brain barrier, making it sensitive to emetogenic substances, and is targeted in antiemetic drug development.
MCQ 9:
Which artery primarily supplies the medulla oblongata?
a) Basilar artery
b) Vertebral artery
c) Anterior cerebral artery
d) Posterior cerebral artery
Answer & Explanation:
Correct answer: b) Vertebral artery.
Explanation: The vertebral arteries supply the medulla oblongata via branches such as the anterior and posterior spinal arteries and PICA. Vascular compromise leads to medullary infarcts, manifesting as life-threatening syndromes like Wallenberg syndrome or respiratory arrest.
MCQ 10 (Clinical):
Key function of medulla oblongata?
a) Visual processing
b) Autonomic control
c) Language comprehension
d) Hormone secretion
Answer & Explanation:
Correct answer: b) Autonomic control.
Explanation: The medulla oblongata regulates essential autonomic functions like heart rate, respiration, blood pressure, and reflex actions such as coughing and vomiting. Lesions can cause life-threatening autonomic dysfunction, highlighting its clinical importance.
Topic: Neuroanatomy
Subtopic: Thalamic Nuclei and Cerebral Cortex Connections
Keywords:
Thalamic Nuclei: Clusters of neurons in the thalamus relaying sensory and motor signals to the cerebral cortex.
Neocortex: The part of the cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, and motor control.
Pulvinar Nucleus: Largest thalamic nucleus involved in visual attention and connects to association areas of neocortex.
Intralaminar Nuclei: Involved in arousal, attention, and pain perception, projecting diffusely to cortex.
Anterior Nucleus: Connected to limbic system and involved in memory processing, projecting to cingulate gyrus.
Lead Question - 2013:
Which thalamic nuclei connects with neocortex?
a) Pulvinar
b) Intralaminar
c) Anterior
d) All
Answer & Explanation:
Correct answer: d) All.
Explanation: All listed thalamic nuclei—Pulvinar, Intralaminar, and Anterior—connect with the neocortex. Pulvinar is important in visual attention, Intralaminar nuclei help in arousal and attention, and the Anterior nucleus participates in memory functions. Their integration ensures complex cortical processing and behavior regulation.
MCQ 1:
The main role of pulvinar nucleus is?
a) Motor coordination
b) Visual attention
c) Auditory processing
d) Hormonal regulation
Answer & Explanation:
Correct answer: b) Visual attention.
Explanation: The pulvinar nucleus plays a major role in visual attention by connecting with visual association areas in the neocortex. It helps in filtering and prioritizing visual information, which is vital for focused attention and perception of complex stimuli.
MCQ 2:
Which thalamic nuclei is primarily involved in arousal and alertness?
a) Anterior nucleus
b) Pulvinar nucleus
c) Intralaminar nuclei
d) Medial geniculate nucleus
Answer & Explanation:
Correct answer: c) Intralaminar nuclei.
Explanation: Intralaminar nuclei are diffusely connected to the neocortex and are crucial in arousal, attention, and awareness. They are often implicated in disorders of consciousness and are a focus of research in disorders like coma and vegetative states.
MCQ 3:
Anterior nucleus of the thalamus projects to?
a) Visual cortex
b) Prefrontal cortex
c) Cingulate gyrus
d) Auditory cortex
Answer & Explanation:
Correct answer: c) Cingulate gyrus.
Explanation: The anterior nucleus of the thalamus connects to the cingulate gyrus, playing a role in memory and emotional processing. Lesions can lead to memory disturbances and behavioral changes due to its link with the limbic system.
MCQ 4 (Clinical):
Lesion in pulvinar nucleus may cause:
a) Visual neglect
b) Motor weakness
c) Hearing loss
d) Memory loss
Answer & Explanation:
Correct answer: a) Visual neglect.
Explanation: Pulvinar nucleus lesions can lead to visual neglect, especially in the contralateral visual field, due to its role in visual attention and integration. It demonstrates the clinical importance of thalamic pathways in higher cortical functions.
MCQ 5:
Which nuclei is least involved in direct sensory relay?
a) Anterior nucleus
b) Lateral geniculate nucleus
c) Medial geniculate nucleus
d) Ventral posterior nucleus
Answer & Explanation:
Correct answer: a) Anterior nucleus.
Explanation: The anterior nucleus primarily connects with the limbic system for memory and emotion, not directly involved in primary sensory relay, unlike the lateral and medial geniculate nuclei and ventral posterior nucleus that relay visual, auditory, and somatosensory information respectively.
MCQ 6 (Clinical):
Thalamic stroke involving which nuclei causes significant arousal deficit?
a) Ventral posterior nucleus
b) Intralaminar nuclei
c) Lateral geniculate nucleus
d) Anterior nucleus
Answer & Explanation:
Correct answer: b) Intralaminar nuclei.
Explanation: Intralaminar nuclei are critical for arousal and consciousness. Thalamic strokes affecting these nuclei can cause coma or severe arousal deficits, emphasizing their importance in consciousness and attentional mechanisms in clinical neurology.
MCQ 7:
The medial geniculate nucleus of the thalamus connects to?
a) Auditory cortex
b) Visual cortex
c) Motor cortex
d) Somatosensory cortex
Answer & Explanation:
Correct answer: a) Auditory cortex.
Explanation: The medial geniculate nucleus relays auditory information from the inferior colliculus to the auditory cortex, enabling hearing perception and auditory processing. Damage to this pathway can cause hearing deficits or auditory agnosia.
MCQ 8 (Clinical):
Damage to anterior thalamic nucleus causes?
a) Memory deficits
b) Visual loss
c) Hearing impairment
d) Motor weakness
Answer & Explanation:
Correct answer: a) Memory deficits.
Explanation: The anterior nucleus is part of the Papez circuit and plays a crucial role in memory processing. Lesions lead to amnesia and disorientation, frequently observed in thalamic stroke syndromes affecting cognition and memory function.
MCQ 9:
Which thalamic nuclei relays somatosensory information?
a) Anterior nucleus
b) Medial geniculate nucleus
c) Ventral posterior nucleus
d) Pulvinar nucleus
Answer & Explanation:
Correct answer: c) Ventral posterior nucleus.
Explanation: The ventral posterior nucleus of the thalamus is the main relay station for somatosensory information from the body and face to the primary somatosensory cortex, crucial in sensory perception and clinical examination.
MCQ 10 (Clinical):
Thalamic pain syndrome (Dejerine-Roussy) is associated with damage to?
a) Anterior nucleus
b) Pulvinar nucleus
c) Ventral posterior nucleus
d) Medial geniculate nucleus
Answer & Explanation:
Correct answer: c) Ventral posterior nucleus.
Explanation: Dejerine-Roussy syndrome occurs due to damage to the ventral posterior nucleus, causing chronic contralateral pain, sensory disturbances, and allodynia. Recognition is important for diagnosis and management of post-stroke pain syndromes.
Topic: Ear Anatomy
Subtopic: Stapedius Nerve
Keywords:
Stapedius Nerve: A small branch of the facial nerve that innervates the stapedius muscle in the middle ear.
Trigeminal Nerve (CN V): Supplies motor function to muscles of mastication and sensory to face.
Facial Nerve (CN VII): Provides motor innervation to facial muscles and carries taste and parasympathetic fibers.
Vagus Nerve (CN X): Supplies parasympathetic fibers to thoracic and abdominal organs and sensory/motor fibers to larynx and pharynx.
Lead Question - 2013:
Stapedius nerve is a branch of?
a) Trigeminal nerve
b) Facial nerve
c) Vagus nerve
d) None
Answer & Explanation:
Correct answer: b) Facial nerve.
Explanation: The stapedius nerve is a branch of the facial nerve (CN VII). It innervates the stapedius muscle in the middle ear, which stabilizes the stapes bone to dampen loud sounds. Dysfunction can lead to hyperacusis, highlighting the nerve's clinical importance in auditory protection and sound modulation.
MCQ 1:
The stapedius muscle helps to:
a) Amplify sound
b) Stabilize the stapes
c) Transmit sound to the cochlea
d) Open the Eustachian tube
Answer & Explanation:
Correct answer: b) Stabilize the stapes.
Explanation: The stapedius muscle dampens excessive vibrations of the stapes bone to protect the inner ear from loud sounds. Innervated by the stapedius nerve (branch of facial nerve), its dysfunction causes hyperacusis. Understanding this helps in diagnosing auditory sensitivity disorders after middle ear pathology or surgery.
MCQ 2:
Damage to the facial nerve can cause which auditory symptom?
a) Sensorineural hearing loss
b) Conductive hearing loss
c) Hyperacusis
d) Tinnitus
Answer & Explanation:
Correct answer: c) Hyperacusis.
Explanation: Damage to the stapedius nerve branch of the facial nerve results in paralysis of the stapedius muscle. This reduces damping of sound vibrations, leading to hyperacusis—an increased sensitivity to normal sounds. Recognizing this is essential in facial nerve palsy evaluations to assess auditory system involvement.
MCQ 3:
The stapedius nerve emerges from which part of the facial nerve?
a) Intracranial segment
b) Geniculate ganglion
c) Tympanic segment
d) Mastoid segment
Answer & Explanation:
Correct answer: c) Tympanic segment.
Explanation: The stapedius nerve branches from the tympanic segment of the facial nerve. It passes through the middle ear to innervate the stapedius muscle. Knowledge of this anatomy is critical during middle ear surgery to avoid damaging the nerve, which would cause hyperacusis and affect sound modulation.
MCQ 4 (Clinical):
A patient with Bell's palsy reports sensitivity to loud sounds. Which nerve is likely involved?
a) Auriculotemporal nerve
b) Vestibulocochlear nerve
c) Stapedius nerve
d) Glossopharyngeal nerve
Answer & Explanation:
Correct answer: c) Stapedius nerve.
Explanation: In Bell's palsy, the facial nerve is inflamed or compressed, potentially affecting the stapedius nerve. This leads to hyperacusis due to lack of stapes stabilization. Identifying this clinical sign aids in diagnosis and indicates the extent of facial nerve involvement.
MCQ 5:
The primary function of the stapedius muscle is to:
a) Transmit sound to the cochlea
b) Amplify high-frequency sounds
c) Stabilize the stapes during loud noise
d) Regulate middle ear pressure
Answer & Explanation:
Correct answer: c) Stabilize the stapes during loud noise.
Explanation: The stapedius muscle contracts in response to loud sounds, stabilizing the stapes to dampen excessive vibration and protect the inner ear. This reflex, known as the acoustic reflex, is essential for auditory system protection and is mediated via the facial nerve pathway.
MCQ 6 (Clinical):
Which condition may result from stapedius muscle paralysis?
a) Otosclerosis
b) Hyperacusis
c) Conductive hearing loss
d) Vertigo
Answer & Explanation:
Correct answer: b) Hyperacusis.
Explanation: Paralysis of the stapedius muscle due to stapedius nerve damage removes its dampening effect on stapes movement. This leads to hyperacusis, where normal environmental sounds are perceived as excessively loud and uncomfortable. Understanding this helps differentiate auditory hypersensitivity disorders from other hearing impairments.
MCQ 7:
The stapedius muscle attaches to which auditory ossicle?
a) Malleus
b) Incus
c) Stapes
d) Tympanic membrane
Answer & Explanation:
Correct answer: c) Stapes.
Explanation: The stapedius muscle attaches to the neck of the stapes, the smallest bone in the human body. Its contraction stabilizes the stapes to modulate sound transmission. Injury to the stapedius nerve affects this function, emphasizing the importance of precise anatomical knowledge during middle ear surgeries.
MCQ 8 (Clinical):
During middle ear surgery, which nerve is at risk of damage affecting auditory sensitivity?
a) Facial nerve
b) Auditory nerve
c) Chorda tympani
d) Stapedius nerve
Answer & Explanation:
Correct answer: d) Stapedius nerve.
Explanation: The stapedius nerve traverses the middle ear cavity, making it vulnerable during procedures like stapedectomy. Damage results in stapedius muscle paralysis and hyperacusis. Surgeons must carefully navigate the middle ear anatomy to preserve this nerve and prevent postoperative auditory sensitivity disorders.
MCQ 9:
The stapedius reflex is primarily a protective mechanism against:
a) Low-frequency sounds
b) High-intensity sounds
c) Continuous ambient noise
d) Vestibular imbalance
Answer & Explanation:
Correct answer: b) High-intensity sounds.
Explanation: The stapedius reflex, mediated by the stapedius nerve, contracts the stapedius muscle in response to high-intensity sounds. This reduces the transmission of sound energy to the inner ear, protecting cochlear hair cells. Clinical tests of this reflex assess middle ear and facial nerve integrity.
MCQ 10 (Clinical):
A patient with congenital absence of the stapedius muscle experiences:
a) Complete deafness
b) Hyperacusis
c) Vertigo
d) Tinnitus
Answer & Explanation:
Correct answer: b) Hyperacusis.
Explanation: Congenital absence of the stapedius muscle prevents normal damping of stapes vibrations, leading to hyperacusis. Patients perceive everyday sounds as painfully loud. This emphasizes the stapedius muscle’s protective role and the importance of assessing auditory reflexes in patients with unexplained sound sensitivity.
Chapter: Anatomy
Topic: Nervous System
Subtopic: Nerve Anastomosis
Keywords:
Galen's Anastomosis: A nerve connection between the internal and external laryngeal nerves.
Recurrent Laryngeal Nerve: Branch of the vagus nerve supplying motor function to intrinsic laryngeal muscles.
Internal Laryngeal Nerve: Provides sensation to the laryngeal mucosa above the vocal cords.
External Laryngeal Nerve: Supplies the cricothyroid muscle responsible for pitch modulation.
Lead Question - 2013:
Galen's anastomosis is between ?
a) Recurrent laryngeal nerve and external laryngeal nerve
b) Recurrent laryngeal nerve and internal laryngeal nerve
c) Internal laryngeal nerve and external laryngeal nerve
d) None of the above
Answer & Explanation:
Correct answer: c) Internal laryngeal nerve and external laryngeal nerve.
Explanation: Galen's anastomosis refers to the communication between the internal and external laryngeal nerves. This connection is significant for overlapping sensory and motor innervation in the larynx, ensuring coordinated function. Understanding this anastomosis is important in surgeries to avoid vocal complications.
MCQ 1
Which nerve provides sensation above the vocal cords?
a) Recurrent laryngeal nerve
b) Internal laryngeal nerve
c) External laryngeal nerve
d) Hypoglossal nerve
Answer & Explanation:
Correct answer: b) Internal laryngeal nerve.
Explanation: The internal laryngeal nerve supplies sensory innervation to the laryngeal mucosa above the vocal cords. This nerve plays a crucial role in the cough reflex, preventing aspiration. Damage can lead to loss of sensation and predispose to aspiration pneumonia in clinical practice.
MCQ 2
The cricothyroid muscle is innervated by which nerve?
a) Recurrent laryngeal nerve
b) Internal laryngeal nerve
c) External laryngeal nerve
d) Accessory nerve
Answer & Explanation:
Correct answer: c) External laryngeal nerve.
Explanation: The external laryngeal nerve innervates the cricothyroid muscle, which adjusts vocal cord tension and modulates pitch. Clinically, damage may result in hoarseness. Understanding this is vital during thyroid surgeries to prevent vocal changes.
MCQ 3
Which statement about the recurrent laryngeal nerve is true?
a) It supplies the cricothyroid muscle.
b) It provides sensation above the vocal cords.
c) It supplies all intrinsic laryngeal muscles except the cricothyroid.
d) It is a branch of the external carotid artery.
Answer & Explanation:
Correct answer: c) It supplies all intrinsic laryngeal muscles except the cricothyroid.
Explanation: The recurrent laryngeal nerve provides motor supply to all intrinsic laryngeal muscles except the cricothyroid. This anatomical detail is crucial during neck surgeries, as injury can cause vocal cord paralysis and hoarseness.
MCQ 4 (Clinical):
A patient presents with hoarseness post-thyroidectomy. Which nerve is most likely injured?
a) Internal laryngeal nerve
b) External laryngeal nerve
c) Recurrent laryngeal nerve
d) Hypoglossal nerve
Answer & Explanation:
Correct answer: c) Recurrent laryngeal nerve.
Explanation: The recurrent laryngeal nerve is prone to injury during thyroidectomy due to its anatomical proximity. Injury leads to hoarseness or loss of voice, as it innervates the intrinsic laryngeal muscles except cricothyroid. Early recognition is essential to manage vocal dysfunction.
MCQ 5
What is the function of the external laryngeal nerve?
a) Sensory innervation above vocal cords
b) Motor supply to cricothyroid muscle
c) Motor supply to all intrinsic laryngeal muscles
d) Sensory innervation below vocal cords
Answer & Explanation:
Correct answer: b) Motor supply to cricothyroid muscle.
Explanation: The external laryngeal nerve provides motor innervation to the cricothyroid muscle, essential for modulating voice pitch. Injury affects high-pitched voice production. Knowledge of this nerve’s function aids clinicians in assessing voice disorders after surgery.
MCQ 6 - (Clinical)
Which anastomosis ensures backup sensory innervation if one laryngeal nerve is damaged?
a) Galen's anastomosis
b) Beclard's anastomosis
c) Thyrohyoid anastomosis
d) Ansell’s anastomosis
Answer & Explanation:
Correct answer: a) Galen's anastomosis.
Explanation: Galen's anastomosis connects the internal and external laryngeal nerves, providing backup sensory innervation. This redundancy ensures partial preservation of laryngeal sensation if one nerve is injured, reducing clinical deficits like aspiration.
MCQ 7
Which nerve loops around the aortic arch on the left side?
a) External laryngeal nerve
b) Internal laryngeal nerve
c) Left recurrent laryngeal nerve
d) Right recurrent laryngeal nerve
Answer & Explanation:
Correct answer: c) Left recurrent laryngeal nerve.
Explanation: The left recurrent laryngeal nerve loops around the aortic arch, while the right loops around the subclavian artery. This anatomical variation is important for surgeons to avoid inadvertent injury during mediastinal procedures.
MCQ 8 - (Clinical):
A patient has loss of high-pitched voice but normal cough reflex. Which nerve is likely damaged?
a) Recurrent laryngeal nerve
b) Internal laryngeal nerve
c) External laryngeal nerve
d) Hypoglossal nerve
Answer & Explanation:
Correct answer: c) External laryngeal nerve.
Explanation: The external laryngeal nerve controls the cricothyroid muscle, affecting pitch modulation. Its damage leads to loss of high-pitched voice without affecting the cough reflex, which depends on the internal laryngeal nerve.
MCQ 9
Which nerve is primarily responsible for cough reflex initiation?
a) External laryngeal nerve
b) Internal laryngeal nerve
c) Recurrent laryngeal nerve
d) Glossopharyngeal nerve
Answer & Explanation:
Correct answer: b) Internal laryngeal nerve.
Explanation: The internal laryngeal nerve provides sensory input to the larynx above vocal cords and is critical for initiating the cough reflex. Damage to this nerve impairs protective reflexes, leading to aspiration risk in patients.
MCQ 10 - (Clinical):
During surgery, accidental cutting of which nerve affects voice pitch but not vocal cord movement?
a) Internal laryngeal nerve
b) External laryngeal nerve
c) Recurrent laryngeal nerve
d) Vagus nerve
Answer & Explanation:
Correct answer: b) External laryngeal nerve.
Explanation: The external laryngeal nerve innervates the cricothyroid muscle, controlling voice pitch. Injury does not paralyze vocal cords but impairs pitch modulation, leading to monotonous speech. Surgeons must carefully preserve this nerve during thyroid and neck surgeries.
Topic: Nerve Supply of Larynx
Subtopic: Innervation of Intrinsic Laryngeal Muscles
Keyword Definitions:
Recurrent Laryngeal Nerve: Branch of the vagus nerve supplying all intrinsic laryngeal muscles except the cricothyroid.
Cricothyroid Muscle: Muscle that adjusts tension of vocal cords, supplied by the external branch of superior laryngeal nerve.
Vocalis Muscle: Intrinsic laryngeal muscle controlling fine tension of the vocal cords.
Thyroarytenoid Muscle: Muscle relaxing vocal cords, aiding in sound modulation.
Interarytenoid Muscle: Muscle that adducts arytenoid cartilages, closing the posterior laryngeal inlet.
Lead Question - 2013
Which muscle of larynx is not supplied by recurrent laryngeal nerve?
a) Vocalis
b) Thyroarytenoid
c) Cricothyroid
d) Interarytenoid
Explanation: The cricothyroid muscle is the only intrinsic laryngeal muscle not supplied by the recurrent laryngeal nerve. Instead, it receives innervation from the external branch of the superior laryngeal nerve and is responsible for tensing the vocal cords to modulate voice pitch. Correct answer is c) Cricothyroid.
Guessed Question 2
Lesion of recurrent laryngeal nerve causes:
a) Loss of voice pitch modulation
b) Hoarseness or aphonia
c) Loss of sensation above vocal cords
d) Loss of sensation below vocal cords
Explanation: A lesion of the recurrent laryngeal nerve affects motor supply to all intrinsic laryngeal muscles except the cricothyroid, resulting in hoarseness, voice fatigue, or even aphonia. Sensory loss below the vocal cords may also occur. Correct answer is b) Hoarseness or aphonia.
Guessed Question 3
External branch of superior laryngeal nerve innervates:
a) Vocalis
b) Cricothyroid
c) Thyroarytenoid
d) Interarytenoid
Explanation: The external branch of the superior laryngeal nerve provides motor innervation to the cricothyroid muscle, which is crucial for regulating vocal cord tension and pitch. Other intrinsic muscles are supplied by the recurrent laryngeal nerve. Correct answer is b) Cricothyroid.
Guessed Question 4
Internal branch of superior laryngeal nerve provides:
a) Motor supply to cricothyroid
b) Sensory to larynx above vocal cords
c) Sensory to larynx below vocal cords
d) Motor supply to interarytenoid
Explanation: The internal branch of the superior laryngeal nerve supplies sensory innervation to the laryngeal mucosa above the vocal cords. It does not have a motor function. Recurrent laryngeal nerve supplies motor innervation below vocal cords. Correct answer is b) Sensory to larynx above vocal cords.
Guessed Question 5
Recurrent laryngeal nerve arises from the vagus nerve at which level on the right side?
a) Arch of aorta
b) Subclavian artery
c) Common carotid artery
d) Carotid sheath
Explanation: On the right side, the recurrent laryngeal nerve arises from the vagus nerve at the level of the subclavian artery, looping around it before ascending toward the larynx. This anatomical pathway makes it vulnerable during surgery. Correct answer is b) Subclavian artery.
Guessed Question 6
Which structure is at risk of injury in thyroid surgery?
a) Internal laryngeal nerve
b) Recurrent laryngeal nerve
c) External carotid artery
d) Vagus nerve trunk
Explanation: The recurrent laryngeal nerve is at risk during thyroid surgeries because of its close anatomical relationship to the thyroid gland. Injury leads to vocal cord paralysis, hoarseness, or airway obstruction. Careful dissection is required to avoid this complication. Correct answer is b) Recurrent laryngeal nerve.
Guessed Question 7
Which of the following is NOT an intrinsic laryngeal muscle?
a) Thyroarytenoid
b) Cricothyroid
c) Sternohyoid
d) Vocalis
Explanation: The sternohyoid muscle is an extrinsic laryngeal muscle involved in depressing the hyoid bone and larynx. The intrinsic muscles, such as thyroarytenoid, cricothyroid, and vocalis, control vocal cord tension and position. Correct answer is c) Sternohyoid.
Guessed Question 8
Which nerve carries parasympathetic fibers to the larynx?
a) Glossopharyngeal
b) Vagus
c) Hypoglossal
d) Spinal accessory
Explanation: The vagus nerve (CN X) carries parasympathetic fibers to the larynx, in addition to its sensory and motor functions. It plays a role in regulating secretions and blood flow in the larynx. Correct answer is b) Vagus.
Guessed Question 9
The internal branch of superior laryngeal nerve enters the larynx through which structure?
a) Cricothyroid membrane
b) Thyrohyoid membrane
c) Jugular foramen
d) Carotid canal
Explanation: The internal branch of the superior laryngeal nerve penetrates the thyrohyoid membrane to provide sensory innervation to the larynx above the vocal cords. This passage is clinically important during procedures like laryngeal blocks. Correct answer is b) Thyrohyoid membrane.
Guessed Question 10
External laryngeal nerve is a branch of which nerve?
a) Vagus nerve
b) Glossopharyngeal nerve
c) Hypoglossal nerve
d) Facial nerve
Explanation: The external laryngeal nerve is a branch of the vagus nerve (CN X) and provides motor innervation to the cricothyroid muscle. Its damage affects pitch modulation, leading to monotone voice. Correct answer is a) Vagus nerve.
Topic: Nerve Supply of Larynx
Subtopic: Innervation of Larynx
Keyword Definitions:
Larynx: An organ located in the neck involved in breathing, producing sound, and protecting the trachea against food aspiration.
Superior Laryngeal Nerve: Branch of the vagus nerve (CN X) that provides sensation above the vocal cords and motor supply to the cricothyroid muscle.
Recurrent Laryngeal Nerve: Branch of the vagus nerve looping around major arteries; provides motor supply to intrinsic laryngeal muscles and sensation below the vocal cords.
Glossopharyngeal Nerve: Cranial nerve IX, involved in taste, sensory supply to pharynx, and carotid body functions, not directly involved in laryngeal innervation.
External Laryngeal Nerve: Branch of the superior laryngeal nerve supplying the cricothyroid muscle.
Lead Question - 2013
Nerve supply of larynx above level of vocal cord?
a) Superior laryngeal
b) Recurrent laryngeal
c) Glossopharyngeal
d) External laryngeal
Explanation: The larynx above the vocal cords receives sensory innervation from the internal branch of the superior laryngeal nerve, which is a branch of the vagus nerve (CN X). This nerve is essential for protective reflexes and sensation. Recurrent laryngeal supplies below the vocal cords. Correct answer is a) Superior laryngeal.
Guessed Question 2
Which nerve supplies the cricothyroid muscle?
a) Recurrent laryngeal
b) Internal laryngeal
c) External laryngeal
d) Glossopharyngeal
Explanation: The external branch of the superior laryngeal nerve supplies the cricothyroid muscle, responsible for tensing the vocal cords and modulating pitch. Damage causes monotone voice. Recurrent laryngeal nerve supplies other intrinsic laryngeal muscles. Correct answer is c) External laryngeal.
Guessed Question 3
Recurrent laryngeal nerve provides motor supply to:
a) Cricothyroid
b) All intrinsic laryngeal muscles except cricothyroid
c) Only vocalis muscle
d) None of the above
Explanation: The recurrent laryngeal nerve supplies motor innervation to all intrinsic muscles of the larynx except the cricothyroid, which is supplied by the external laryngeal nerve. This is clinically significant in thyroid surgeries. Correct answer is b) All intrinsic laryngeal muscles except cricothyroid.
Guessed Question 4
Sensory supply below vocal cords is provided by?
a) Glossopharyngeal nerve
b) Internal laryngeal nerve
c) Recurrent laryngeal nerve
d) External laryngeal nerve
Explanation: The recurrent laryngeal nerve provides sensory innervation to the larynx below the vocal cords and motor supply to the intrinsic muscles, except the cricothyroid. This is important for cough reflex and surgical risk. Correct answer is c) Recurrent laryngeal nerve.
Guessed Question 5
Injury to superior laryngeal nerve results in:
a) Loss of sensation below vocal cords
b) Loss of high-pitched voice
c) Complete voice loss
d) Horner's syndrome
Explanation: Injury to the superior laryngeal nerve, particularly its external branch, affects the cricothyroid muscle, resulting in loss of pitch modulation, especially high-pitched sounds. The recurrent laryngeal nerve injury causes hoarseness but not high-pitched voice loss specifically. Correct answer is b) Loss of high-pitched voice.
Guessed Question 6
Internal branch of superior laryngeal nerve provides:
a) Motor to intrinsic laryngeal muscles
b) Sensory above vocal cords
c) Sensory below vocal cords
d) Motor to cricothyroid
Explanation: The internal branch of superior laryngeal nerve provides sensory innervation to the mucosa of the larynx above the vocal cords, important in protective airway reflexes like cough. It does not supply motor fibers. Correct answer is b) Sensory above vocal cords.
Guessed Question 7
Which nerve is most at risk during thyroid surgery?
a) Internal laryngeal
b) Recurrent laryngeal
c) External laryngeal
d) Glossopharyngeal
Explanation: The recurrent laryngeal nerve is particularly vulnerable during thyroidectomy, as it courses close to the thyroid gland. Injury leads to vocal cord paralysis, hoarseness, or airway obstruction. Careful dissection avoids damage. Correct answer is b) Recurrent laryngeal.
Guessed Question 8
The superior laryngeal nerve is a branch of which cranial nerve?
a) CN IX
b) CN X
c) CN XI
d) CN XII
Explanation: The superior laryngeal nerve is a branch of the vagus nerve (Cranial Nerve X). It divides into internal and external branches, providing sensory and motor innervation of the larynx. Correct answer is b) CN X.
Guessed Question 9
Function of cricothyroid muscle is to:
a) Adduct vocal cords
b) Abduct vocal cords
c) Tense vocal cords
d) Relax vocal cords
Explanation: The cricothyroid muscle, innervated by the external branch of the superior laryngeal nerve, tenses the vocal cords, increasing pitch. It is essential for modulating voice frequency. Injury leads to monotone voice. Correct answer is c) Tense vocal cords.
Guessed Question 10
Lesion of internal laryngeal nerve results in:
a) Loss of cough reflex
b) Hoarseness
c) Loss of taste
d) Difficulty swallowing
Explanation: Lesion of the internal laryngeal nerve results in loss of sensation above the vocal cords, impairing the cough reflex and increasing the risk of aspiration pneumonia. It does not cause motor deficits. Correct answer is a) Loss of cough reflex.
Topic: Female Reproductive System
Subtopic: Uterine Anomalies
Keyword Definitions:
Cochleate uterus: Uterus with acute retroflexion, where the body of the uterus is sharply bent backward over the cervix.
Anteflexion: Forward bending of the uterine body over the cervix.
Retroflexion: Backward bending of the uterine body over the cervix.
Uterine anomalies: Variations in uterine shape or structure that can affect fertility or cause symptoms like pain.
Clinical significance: Cochleate uterus may lead to menstrual disorders or infertility due to abnormal uterine positioning.
Cervix: The lower part of the uterus connecting to the vagina, important in childbirth and menstrual flow.
Lead Question - 2013
Cochleate uterus is ?
a) Large uterus
b) Acute anteflexion
c) Acute retroflexion
d) Large cervix
Explanation: Cochleate uterus refers to an abnormal uterine position where the uterine body is sharply retroflexed over the cervix, leading to acute retroflexion. This condition can cause infertility, menstrual irregularities, and pelvic pain. It is not related to large size or anteflexion. Correct answer is c) Acute retroflexion.
Guessed Question 2
Which condition describes forward bending of the uterus?
a) Anteflexion
b) Retroflexion
c) Prolapse
d) Inversion
Explanation: Anteflexion refers to the normal forward bending of the uterus over the cervix. It is a common anatomical variant and not usually associated with clinical problems. Acute retroflexion (cochleate uterus) is the opposite condition. Correct answer is a) Anteflexion.
Guessed Question 3
Major clinical symptom of cochleate uterus may be?
a) Menstrual irregularities
b) Vaginal discharge
c) Asymptomatic
d) Pelvic infection
Explanation: Cochleate uterus may lead to menstrual irregularities and infertility due to mechanical hindrance in menstrual flow or sperm transport. Pelvic pain may also be present due to the abnormal uterine position. Correct answer is a) Menstrual irregularities.
Guessed Question 4
Uterine prolapse is best described as:
a) Downward displacement of uterus
b) Forward bending of uterus
c) Enlargement of uterus
d) Acute retroflexion of uterus
Explanation: Uterine prolapse refers to the downward displacement of the uterus into the vaginal canal, often due to weakening of pelvic support structures. This is different from cochleate uterus, which is a retroflexion. Correct answer is a) Downward displacement of uterus.
Guessed Question 5
Which imaging modality is useful to diagnose uterine position anomalies?
a) Ultrasound
b) X-ray
c) CT Scan
d) PET Scan
Explanation: Ultrasound is the primary imaging modality used to evaluate uterine position and detect anomalies such as cochleate uterus. It is non-invasive and provides real-time anatomical details. Correct answer is a) Ultrasound.
Guessed Question 6
Cochleate uterus may result in difficulty during:
a) Micturition
b) Childbirth
c) Digestion
d) Respiration
Explanation: Cochleate uterus, due to its acute retroflexion, can mechanically obstruct the birth canal and lead to difficulty during childbirth. It is not directly related to digestion or respiration. Correct answer is b) Childbirth.
Guessed Question 7
The cervix connects the uterus to:
a) Rectum
b) Vagina
c) Bladder
d) Peritoneum
Explanation: The cervix is the lower, narrow part of the uterus that connects the uterine cavity with the vagina, allowing passage of menstrual flow and sperm. It does not connect directly to bladder or rectum. Correct answer is b) Vagina.
Guessed Question 8
Which is NOT a common symptom of uterine position anomalies?
a) Dyspareunia
b) Infertility
c) Frequent urination
d) Asthma
Explanation: Uterine position anomalies such as cochleate uterus commonly cause dyspareunia (pain during intercourse), infertility, and urinary symptoms due to pressure effects. Asthma is unrelated. Correct answer is d) Asthma.
Guessed Question 9
Cochleate uterus is best managed by:
a) Hormonal therapy
b) Physiotherapy
c) Surgical correction
d) Antibiotics
Explanation: Severe cases of cochleate uterus with symptoms such as infertility or pain may require surgical correction to reposition the uterus. Hormonal therapy or physiotherapy alone is usually insufficient. Correct answer is c) Surgical correction.
Guessed Question 10
Which of the following is TRUE about retroflexed uterus?
a) Always pathological
b) May be normal variant
c) Causes immediate infertility
d) Must be surgically corrected
Explanation: A retroflexed uterus can be a normal anatomical variant and is often asymptomatic. Not all cases require surgical correction unless associated with symptoms like infertility or pain. Correct answer is b) May be normal variant.
Chapter: Anatomy
Topic: Pelvic Nerves
Subtopic: Pain Pathways in Pelvis
Keyword Definitions:
Pudendal nerve: Somatic nerve supplying perineum, external genitalia, and sphincters.
Sciatic nerve: Largest nerve of body, supplies lower limb but not pelvic viscera.
Autonomic nerves: Sympathetic and parasympathetic nerves controlling involuntary pelvic organ function and mediating visceral pain.
Pelvic pain: Often mediated by autonomic nerve fibers transmitting nociceptive signals from pelvic organs.
Clinical significance: Understanding pain pathways aids diagnosis of pelvic disorders like endometriosis or pelvic inflammatory disease.
Visceral vs Somatic pain: Visceral pain is dull, poorly localized, mediated by autonomic fibers; somatic pain is sharp, well localized.
Lead Question - 2013
Pelvic pain is mediated by ?
a) Pudendal nerve
b) Sciatic nerve
c) Autonomic nerves
d) None of the above
Explanation: Pelvic pain, especially from internal pelvic organs like uterus, bladder, or rectum, is primarily mediated by autonomic (sympathetic and parasympathetic) nerves. These nerves carry visceral afferent fibers responsible for dull, poorly localized pain sensations. Pudendal and sciatic nerves are somatic and do not mediate visceral pelvic pain. Correct answer is c) Autonomic nerves.
Guessed Question 2
Which nerve supplies the external genitalia and perineum?
a) Pudendal nerve
b) Sciatic nerve
c) Pelvic splanchnic nerve
d) Obturator nerve
Explanation: The pudendal nerve provides motor and sensory innervation to the external genitalia and perineum, important in voluntary control of sphincters. It does not mediate visceral pelvic pain. Correct answer is a) Pudendal nerve.
Guessed Question 3
Visceral pain in pelvis is typically described as?
a) Sharp and localized
b) Dull and poorly localized
c) Burning
d) Electric shock-like
Explanation: Visceral pain in the pelvis is usually dull and poorly localized due to autonomic nerve mediation. It contrasts with somatic pain, which is sharp and well localized. Correct answer is b) Dull and poorly localized.
Guessed Question 4
Which of the following nerves carries parasympathetic fibers to pelvic organs?
a) Pudendal nerve
b) Pelvic splanchnic nerve
c) Hypogastric nerve
d) Sciatic nerve
Explanation: The pelvic splanchnic nerves (S2-S4) carry parasympathetic fibers to pelvic organs, regulating functions such as bladder contraction and genital erection. These are involved in autonomic control but not in direct somatic pain transmission. Correct answer is b) Pelvic splanchnic nerve.
Guessed Question 5
Sympathetic fibers mediating pelvic pain originate from which spinal segments?
a) T1-T5
b) T10-L2
c) S2-S4
d) L4-L5
Explanation: Sympathetic fibers mediating pelvic visceral pain primarily originate from spinal segments T10 to L2, traveling via hypogastric plexus to pelvic organs. These pathways carry nociceptive signals in disease states. Correct answer is b) T10-L2.
Guessed Question 6
Which of the following is true regarding somatic pelvic pain?
a) Mediated by autonomic nerves
b) Poorly localized
c) Sharp and well localized
d) Does not involve nerve endings
Explanation: Somatic pelvic pain is sharp and well localized because it is mediated by somatic nerves like the pudendal nerve, which carries precise sensory input from skin, muscles, and deeper somatic structures. Correct answer is c) Sharp and well localized.
Guessed Question 7
Pudendal nerve block is used for:
a) Pain relief during childbirth
b) Lower limb surgery
c) Appendectomy
d) Hernia repair
Explanation: Pudendal nerve block is commonly used for analgesia during childbirth, targeting somatic nerves supplying the perineum and external genitalia. It does not block autonomic-mediated visceral pain. Correct answer is a) Pain relief during childbirth.
Guessed Question 8
Which nerve is NOT involved in transmitting pelvic visceral pain?
a) Pelvic splanchnic nerve
b) Hypogastric nerve
c) Pudendal nerve
d) Vagus nerve
Explanation: The pudendal nerve is primarily somatic, serving perineum and external genitalia, and does not carry visceral afferents. Visceral pain is mediated by pelvic splanchnic, hypogastric, and vagus nerves. Correct answer is c) Pudendal nerve.
Guessed Question 9
Visceral pelvic pain is aggravated by:
a) Movement
b) Organ distension
c) Skin irritation
d) Muscle contraction
Explanation: Visceral pelvic pain is often aggravated by organ distension or ischemia due to stretch-sensitive receptors in autonomic nerves. Movement or somatic stimuli typically affect somatic pain. Correct answer is b) Organ distension.
Guessed Question 10
Which of the following is NOT a function of autonomic nerves in pelvis?
a) Regulate bladder contraction
b) Mediate erection
c) Innervate external anal sphincter
d) Transmit visceral pain
Explanation: Autonomic nerves regulate involuntary functions like bladder contraction, genital erection, and visceral pain. The external anal sphincter is innervated by somatic pudendal nerve, not autonomic nerves. Correct answer is c) Innervate external anal sphincter.
Chapter: Anatomy
Topic: Pelvis and Perineum
Subtopic: Sacrotuberous Ligament and Related Structures
Keyword Definitions:
Sacrotuberous Ligament: Strong ligament connecting sacrum to ischial tuberosity, stabilizing the sacroiliac joint.
Perforating Cutaneous Nerve: Small branch of sacral plexus that pierces sacrotuberous ligament to supply buttock skin.
Posterior Femoral Cutaneous Nerve: Nerve supplying posterior thigh and gluteal skin, passing beneath gluteus maximus.
Sciatic Nerve: Largest nerve of the body, leaves pelvis via greater sciatic foramen below piriformis.
Superior Gluteal Nerve: Nerve passing through greater sciatic foramen above piriformis to supply gluteus medius, minimus, and tensor fascia lata.
Clinical Relevance: Injury to sacrotuberous ligament region can cause entrapment neuropathy or gluteal pain syndromes.
Lead Question - 2013
Sacrotuberous ligament is pierced by
a) Perforating cutaneous nerve
b) Posterior femoral cutaneous
c) Superior gluteal nerve
d) Sciatic nerve
Explanation: The sacrotuberous ligament is pierced only by the perforating cutaneous nerve, which arises from the sacral plexus and supplies the medial gluteal region skin. Other nerves pass through sciatic foramina. The correct answer is a) Perforating cutaneous nerve.
Guessed Question 2
Which ligament forms the lower boundary of the lesser sciatic foramen?
a) Sacrospinous ligament
b) Sacrotuberous ligament
c) Inguinal ligament
d) Obturator membrane
Explanation: The sacrotuberous ligament extends from sacrum to ischial tuberosity, forming the lower boundary of lesser sciatic foramen. The sacrospinous ligament forms its upper boundary. The correct answer is b) Sacrotuberous ligament.
Guessed Question 3
Which nerve passes below the piriformis through the greater sciatic foramen?
a) Sciatic nerve
b) Superior gluteal nerve
c) Obturator nerve
d) Femoral nerve
Explanation: The sciatic nerve passes through the greater sciatic foramen below piriformis, running deep to gluteus maximus. Compression here may cause sciatica. The correct answer is a) Sciatic nerve.
Guessed Question 4
Which ligament along with sacrospinous converts sciatic notch into foramen?
a) Sacrotuberous ligament
b) Iliofemoral ligament
c) Pubofemoral ligament
d) Ischiofemoral ligament
Explanation: Sacrotuberous and sacrospinous ligaments transform greater and lesser sciatic notches into foramina through which pelvic nerves and vessels pass. The correct answer is a) Sacrotuberous ligament.
Guessed Question 5
In piriformis syndrome, which nerve is compressed as it passes beneath piriformis?
a) Sciatic nerve
b) Pudendal nerve
c) Posterior femoral cutaneous nerve
d) Inferior gluteal nerve
Explanation: In piriformis syndrome, the sciatic nerve gets compressed as it passes below piriformis, producing pain radiating to posterior thigh and leg. The correct answer is a) Sciatic nerve.
Guessed Question 6
Which nerve leaves pelvis through the lesser sciatic foramen?
a) Pudendal nerve
b) Superior gluteal nerve
c) Posterior femoral cutaneous nerve
d) Sciatic nerve
Explanation: The pudendal nerve exits through greater sciatic foramen, hooks around ischial spine and sacrospinous ligament, and re-enters through lesser sciatic foramen into the perineum. The correct answer is a) Pudendal nerve.
Guessed Question 7
Which structure passes between sacrotuberous and sacrospinous ligaments?
a) Pudendal nerve
b) Obturator nerve
c) Femoral nerve
d) Genitofemoral nerve
Explanation: Pudendal nerve, internal pudendal vessels, and nerve to obturator internus pass between sacrospinous and sacrotuberous ligaments to enter lesser sciatic foramen. The correct answer is a) Pudendal nerve.
Guessed Question 8
Damage to superior gluteal nerve affects which function?
a) Hip abduction
b) Hip extension
c) Hip adduction
d) Knee flexion
Explanation: Superior gluteal nerve supplies gluteus medius and minimus. Damage weakens hip abduction and causes positive Trendelenburg sign due to failure of pelvic support. The correct answer is a) Hip abduction.
Guessed Question 9
Which ligament resists posterior rotation of sacrum?
a) Sacrotuberous ligament
b) Anterior sacroiliac ligament
c) Iliofemoral ligament
d) Inguinal ligament
Explanation: Sacrotuberous ligament helps resist posterior rotation of sacrum at sacroiliac joint, stabilizing pelvis against body weight. The correct answer is a) Sacrotuberous ligament.
Guessed Question 10
Which nerve supplies posterior thigh skin but does not pierce sacrotuberous ligament?
a) Posterior femoral cutaneous nerve
b) Perforating cutaneous nerve
c) Obturator nerve
d) Pudendal nerve
Explanation: Posterior femoral cutaneous nerve passes below gluteus maximus to supply posterior thigh skin but does not pierce sacrotuberous ligament. The correct answer is a) Posterior femoral cutaneous nerve.
Guessed Question 11
Entrapment of perforating cutaneous nerve causes pain in which region?
a) Medial gluteal region
b) Posterior thigh
c) Perineum
d) Lateral leg
Explanation: The perforating cutaneous nerve, piercing sacrotuberous ligament, supplies medial gluteal region. Entrapment or irritation causes localized gluteal pain. The correct answer is a) Medial gluteal region.
Keyword Definitions
• Flexor retinaculum (ankle) – Fibrous band over medial ankle forming the roof of the tarsal tunnel.
• Tarsal tunnel – Space deep to flexor retinaculum transmitting tendons, vessels, and nerve into the foot.
• Posterior tibial artery – Major artery passing through tarsal tunnel to supply plantar foot; palpable as posterior tibial pulse.
• Tibialis anterior tendon – Anterior compartment tendon crossing dorsum of foot; does NOT pass under flexor retinaculum.
• Peroneus tertius – Anterior-lateral tendon inserting on dorsum of 5th metatarsal; not in tarsal tunnel.
• Long saphenous (great saphenous) vein – Superficial vein running anterior to medial malleolus, superficial to retinaculum.
• Tom, Dick And Very Nervous Harry – Mnemonic for structures deep to flexor retinaculum: Tibialis posterior, flexor Digitorum longus, posterior tibial Artery, posterior tibial Vein, tibial Nerve, flexor Hallucis longus.
• Tinel’s sign (at ankle) – Tapping over flexor retinaculum producing tingling in tunnel distribution, suggests tibial nerve entrapment.
• Posterior tibial pulse – Palpated just posterior to medial malleolus deep to flexor retinaculum; important in vascular exam.
• Clinical relevance – Tarsal tunnel syndrome results from compression of structures under flexor retinaculum causing plantar numbness/pain.
Chapter: Anatomy / Lower Limb
Topic: Ankle Region
Subtopic: Flexor Retinaculum (Tarsal Tunnel) Contents
Lead Question – 2013
Structure passing deep to flexor retinaculum is ?
a) Posterior tibial artery
b) Long saphenous vein
c) Tibialis anterior tendon
d) Peroneus tertius
Explanation: The posterior tibial artery passes deep to the flexor retinaculum within the tarsal tunnel alongside tendons and the tibial nerve. The long saphenous vein is superficial, tibialis anterior and peroneus tertius are anterior tendons. Correct answer: (a) Posterior tibial artery. Clinically the posterior tibial pulse is palpable here.
Guessed Questions for NEET PG
1) The tarsal tunnel contains all EXCEPT:
a) Tibialis posterior tendon
b) Flexor digitorum longus tendon
c) Peroneus longus tendon
d) Posterior tibial nerve
Explanation: The peroneus longus runs laterally and passes under the cuboid (peroneal groove), not through the tarsal tunnel. The tunnel contains tibialis posterior, FDL, posterior tibial vessels, tibial nerve, and FHL. Correct answer: Peroneus longus. Tarsal tunnel syndrome spares lateral tendons.
2) Posterior tibial pulse is best palpated:
a) Anterior to lateral malleolus
b) Posterior to medial malleolus beneath flexor retinaculum
c) On dorsum of foot lateral to EHL tendon
d) In popliteal fossa only
Explanation: The posterior tibial artery runs deep to flexor retinaculum posterior to the medial malleolus; its pulse is palpated there. Correct answer: Posterior to medial malleolus beneath flexor retinaculum. Loss of this pulse suggests distal arterial compromise.
3) Tinel’s sign at the tarsal tunnel tests for entrapment of which nerve?
a) Superficial peroneal nerve
b) Deep peroneal nerve
c) Tibial nerve (posterior tibial nerve in tunnel)
d) Sural nerve
Explanation: Tinel’s tapping over flexor retinaculum reproduces paresthesia in tibial nerve distribution (sole) when entrapped. Correct answer: Tibial nerve. Positive test aids diagnosis of tarsal tunnel syndrome which presents with plantar numbness and burning pain.
4) Which tendon is most medial under the flexor retinaculum (medial to lateral order)?
a) Flexor hallucis longus
b) Tibialis posterior
c) Flexor digitorum longus
d) Peroneus brevis
Explanation: Medial-to-lateral order in tarsal tunnel is tibialis posterior, flexor digitorum longus, posterior tibial vessels/nerve, then flexor hallucis longus more laterally. Peroneal tendons are lateral. Correct answer: Tibialis posterior. Important during surgical decompression.
5) Compression of posterior tibial nerve in the tarsal tunnel causes loss of sensation over:
a) Dorsum of foot only
b) Plantar surface of foot and toes
c) Lateral calf only
d) Medial thigh
Explanation: Tibial nerve supplies plantar cutaneous nerves; entrapment in tarsal tunnel causes plantar burning, numbness, and possible intrinsic muscle weakness. Correct answer: Plantar surface of foot and toes. Tarsal tunnel mimics plantar fasciitis clinically sometimes.
6) A patient with rupture of posterior tibial artery in ankle trauma will most likely present with:
a) Loss of dorsalis pedis pulse only
b) Absent posterior tibial pulse, ischemic plantar changes
c) Isolated foot drop
d) Loss of great saphenous waveform only
Explanation: Rupture of posterior tibial artery abolishes its palpable pulse and can compromise plantar circulation causing ischemic changes. Dorsalis pedis may be maintained via anterior tibial flow. Correct answer: Absent posterior tibial pulse, ischemic plantar changes. Urgent vascular assessment required.
7) The mnemonic “Tom, Dick, And Very Nervous Harry” lists structures in tarsal tunnel in which order?
a) Tibialis posterior, flexor Digitorum longus, posterior tibial Artery, posterior tibial Vein, tibial Nerve, flexor Hallucis longus
b) Tibialis anterior, extensor Digitorum longus, anterior tibial Artery…
c) Peroneus longus, peroneus brevis, sural nerve…
d) Flexor hallucis longus first then others
Explanation: The mnemonic correctly orders tibialis posterior, FDL, posterior tibial artery, posterior tibial vein, tibial nerve, and flexor hallucis longus (from medial to lateral). Correct answer: (a). Surgeons use this to identify structures during decompression.
8) Which vessel provides collateral supply to plantar arch if posterior tibial artery is occluded?
a) Anterior tibial (via dorsalis pedis and perforating branches)
b) Great saphenous vein
c) Peroneal artery exclusively without connections
d) Small saphenous vein
Explanation: Anterior tibial continues as dorsalis pedis and via perforating branches can contribute to plantar arches, providing collateral flow when posterior tibial artery is occluded. Correct answer: Anterior tibial (via dorsalis pedis). Clinical: Important in planning bypass and assessing ischemia.
9) Long saphenous vein at the ankle is located relative to flexor retinaculum as:
a) Deep to retinaculum within tarsal tunnel
b) Superficial to retinaculum anterior to medial malleolus
c) Passing through lateral retinaculum
d) Within tarsal tunnel posterior to tibial nerve
Explanation: The great saphenous vein is superficial on the medial ankle, anterior to the medial malleolus and superficial to the flexor retinaculum, used for venous cutdown access. Correct answer: Superficial to retinaculum anterior to medial malleolus. Preserve saphenous nerve during harvest.
10) Surgical decompression for tarsal tunnel syndrome requires incision of which structure?
a) Flexor retinaculum (tarsal tunnel roof)
b) Extensor retinaculum
c) Plantar aponeurosis only
d) Lateral ankle ligament complex
Explanation: Tarsal tunnel release involves incising the flexor retinaculum to decompress tibial nerve and associated structures. Correct answer: Flexor retinaculum. Timing is important as chronic compression can cause irreversible neuropathy and intrinsic foot muscle atrophy.
Keyword Definitions
• Anterior interosseous nerve (AIN) – A pure motor branch of the median nerve that supplies deep forearm flexors.
• Flexor pollicis longus (FPL) – Muscle of thumb flexion at interphalangeal joint, supplied by AIN.
• Flexor digitorum profundus (FDP) – Medial part supplied by ulnar nerve, lateral part by AIN.
• Flexor digitorum superficialis (FDS) – Flexes proximal interphalangeal joints, supplied by median nerve proper (not AIN).
• Flexor carpi ulnaris (FCU) – Flexes and adducts wrist, supplied by ulnar nerve.
• Brachioradialis – Forearm flexor in mid-pronation, supplied by radial nerve.
• Abductor pollicis brevis (APB) – Thenar muscle, supplied by recurrent branch of median nerve.
• Kiloh–Nevin syndrome – Clinical syndrome due to anterior interosseous nerve palsy.
• Froment’s sign – Indicates ulnar nerve palsy when adductor pollicis is weak.
• Nerve lesions – Important in differential diagnosis of anterior compartment weakness.
Chapter: Anatomy / Upper Limb
Topic: Nerve Supply
Subtopic: Anterior Interosseous Nerve
Lead Question – 2013
All are supplied by anterior interosseous nerve except –
a) Flexor carpi ulnaris
b) Brachioradialis
c) Abductor pollicis brevis
d) Flexor pollicis longus
e) Flexor digitorum superficialis
Explanation: The anterior interosseous nerve supplies flexor pollicis longus, pronator quadratus, and the lateral half of flexor digitorum profundus. Muscles like FCU (ulnar nerve), brachioradialis (radial nerve), APB (recurrent median), and FDS (median nerve proper) are not supplied by AIN. Correct answer: All except FPL.
Guessed Questions for NEET PG
1) Anterior interosseous nerve is a branch of:
a) Ulnar nerve
b) Radial nerve
c) Median nerve
d) Musculocutaneous nerve
Explanation: The anterior interosseous nerve is a motor branch of the median nerve that arises in the proximal forearm. It runs along the interosseous membrane supplying deep flexors. Correct answer: Median nerve. It carries no cutaneous fibers, making its lesions purely motor.
2) Kiloh–Nevin syndrome refers to:
a) Ulnar nerve palsy
b) Radial nerve entrapment
c) Anterior interosseous nerve palsy
d) Posterior interosseous nerve palsy
Explanation: Kiloh–Nevin syndrome is anterior interosseous nerve palsy, presenting with inability to make the “OK sign” due to weakness of FPL and FDP (index finger). Correct answer: Anterior interosseous nerve palsy. It is often due to compression or neuritis.
3) Inability to flex thumb IP joint is seen in lesion of:
a) Median nerve at wrist
b) Ulnar nerve at elbow
c) Anterior interosseous nerve
d) Radial nerve in spiral groove
Explanation: The flexor pollicis longus, innervated by AIN, flexes thumb IP joint. Its palsy causes inability to flex the thumb tip. Correct answer: Anterior interosseous nerve. This finding is a diagnostic clue for AIN syndrome.
4) Which muscle is NOT supplied by AIN?
a) Pronator quadratus
b) FPL
c) FDP (lateral half)
d) FDS
Explanation: The anterior interosseous nerve supplies pronator quadratus, FPL, and lateral half of FDP. The FDS is supplied by the main trunk of the median nerve, not AIN. Correct answer: FDS. This helps localize nerve lesions in clinical practice.
5) Patient unable to flex index finger DIP joint likely has lesion in:
a) Radial nerve
b) Ulnar nerve
c) AIN
d) Musculocutaneous nerve
Explanation: The lateral part of flexor digitorum profundus (index and middle fingers) is supplied by AIN. Inability to flex DIP of index suggests AIN palsy. Correct answer: AIN. Ulnar supplies medial part for ring and little fingers.
6) Which test detects AIN palsy?
a) Phalen’s test
b) Froment’s sign
c) Pinch “OK” sign test
d) Tinel’s sign
Explanation: In AIN palsy, patient cannot make a round “O” with thumb and index, instead forming a triangular pinch due to weakness of FPL and FDP. Correct answer: Pinch “OK” sign test. This is diagnostic of AIN syndrome.
7) Which nerve supplies pronator quadratus?
a) Radial
b) Ulnar
c) Anterior interosseous
d) Posterior interosseous
Explanation: Pronator quadratus, a deep forearm pronator, is supplied exclusively by the anterior interosseous nerve. Correct answer: Anterior interosseous. Lesion impairs pronation, especially when forearm is flexed, and reduces grip strength.
8) A forearm fracture with isolated motor palsy (no sensory loss) indicates lesion of:
a) Ulnar nerve
b) Radial nerve
c) Anterior interosseous nerve
d) Median nerve proper
Explanation: Since the anterior interosseous nerve is a pure motor branch without cutaneous innervation, its injury causes motor weakness only. Correct answer: Anterior interosseous nerve. This differentiates it from other mixed nerves.
9) Which thenar muscle is NOT supplied by anterior interosseous nerve?
a) Abductor pollicis brevis
b) FPL
c) Opponens pollicis
d) Adductor pollicis
Explanation: Abductor pollicis brevis and other thenar muscles are supplied by the recurrent branch of the median nerve. Adductor pollicis is supplied by ulnar. Only FPL is under AIN supply. Correct answer: Abductor pollicis brevis.
10) A patient with supracondylar fracture develops inability to flex thumb IP and index DIP joints. Likely involved nerve is:
a) Radial
b) Ulnar
c) AIN
d) Musculocutaneous
Explanation: This classic presentation is due to AIN palsy following trauma, causing paralysis of FPL and FDP (index). Correct answer: AIN. Distinguishing feature is pure motor deficit with preserved cutaneous sensation.
Keyword Definitions
• Musculocutaneous nerve – Terminal branch of lateral cord of brachial plexus, supplies flexors of arm.
• Brachial plexus – Nerve network supplying upper limb.
• Flexor compartment of arm – Contains biceps brachii, brachialis, and coracobrachialis.
• Biceps brachii – Flexor of elbow, supinator of forearm.
• Coracobrachialis – Flexes and adducts the arm.
• Brachialis – Primary flexor of elbow.
• Radial nerve – Supplies extensor compartment of arm.
• Median nerve – Supplies forearm and hand, not arm flexors.
• Ulnar nerve – Supplies intrinsic hand muscles and part of forearm.
• Clinical test – Elbow flexion and cutaneous sensation of lateral forearm test musculocutaneous nerve.
• Upper limb injuries – Trauma, fractures, or entrapment may affect musculocutaneous nerve function.
Chapter: Anatomy / Upper Limb
Topic: Brachial Plexus
Subtopic: Musculocutaneous Nerve and Arm Flexors
Lead Question – 2013
Nerve supply to the muscles of flexor compartment of arm?
a) Radial nerve
b) Median nerve
c) Musculocutaneous nerve
d) Ulnar nerve
Explanation: The flexor compartment of the arm (biceps brachii, brachialis, coracobrachialis) is innervated by the musculocutaneous nerve, a branch of the lateral cord of the brachial plexus. Correct answer: (c) Musculocutaneous nerve. Clinical: Injury leads to weak elbow flexion and sensory loss over lateral forearm.
Guessed Questions for NEET PG
1) Which nerve continues as the lateral cutaneous nerve of forearm?
a) Radial
b) Median
c) Musculocutaneous
d) Ulnar
Explanation: Musculocutaneous nerve ends as lateral cutaneous nerve of forearm. Correct answer: Musculocutaneous nerve. Clinical: Injury causes sensory loss in lateral forearm.
2) Which muscle is pierced by musculocutaneous nerve?
a) Biceps brachii
b) Coracobrachialis
c) Brachialis
d) Deltoid
Explanation: Musculocutaneous nerve pierces coracobrachialis before supplying flexor compartment. Correct answer: Coracobrachialis. Clinical: Landmark for nerve tracing.
3) Which muscle in flexor compartment also receives supply from radial nerve?
a) Biceps brachii
b) Coracobrachialis
c) Brachialis
d) None
Explanation: Brachialis is mainly supplied by musculocutaneous nerve, but radial nerve gives additional innervation. Correct answer: Brachialis. Clinical: Explains preserved flexion in musculocutaneous injury.
4) Elbow flexion against resistance tests mainly?
a) Median nerve
b) Musculocutaneous nerve
c) Ulnar nerve
d) Axillary nerve
Explanation: Biceps brachii and brachialis, innervated by musculocutaneous nerve, are prime elbow flexors. Correct answer: Musculocutaneous nerve. Clinical: Used to check function.
5) Which branch of brachial plexus gives rise to musculocutaneous nerve?
a) Lateral cord
b) Posterior cord
c) Medial cord
d) Upper trunk
Explanation: Musculocutaneous nerve arises from the lateral cord (C5–C7 roots). Correct answer: Lateral cord. Clinical: Knowledge useful in brachial plexus blocks.
6) Sensory loss over lateral forearm is due to injury of?
a) Radial nerve
b) Musculocutaneous nerve
c) Median nerve
d) Ulnar nerve
Explanation: Lateral cutaneous nerve of forearm (continuation of musculocutaneous) supplies skin here. Correct answer: Musculocutaneous nerve. Clinical: Sensory deficit confirms diagnosis.
7) Which movement is most affected in musculocutaneous nerve injury?
a) Shoulder abduction
b) Elbow flexion
c) Wrist extension
d) Finger flexion
Explanation: Musculocutaneous injury impairs elbow flexion due to paralysis of biceps and brachialis. Correct answer: Elbow flexion. Clinical: Weak supination also observed.
8) A patient with injury to musculocutaneous nerve will show weakness of?
a) Forearm pronation
b) Elbow flexion
c) Finger extension
d) Thumb opposition
Explanation: Injury leads to loss of flexors of arm, causing weak elbow flexion. Correct answer: Elbow flexion. Clinical: Supination also affected due to biceps involvement.
9) Which muscle is absent in flexor compartment if musculocutaneous nerve is injured?
a) Deltoid
b) Coracobrachialis
c) Triceps
d) Supinator
Explanation: Coracobrachialis is supplied by musculocutaneous nerve and loses function in its injury. Correct answer: Coracobrachialis. Clinical: Shoulder adduction and flexion weakened.
10) Which of the following is NOT supplied by musculocutaneous nerve?
a) Biceps brachii
b) Brachialis
c) Coracobrachialis
d) Triceps brachii
Explanation: Triceps brachii belongs to extensor compartment, supplied by radial nerve. Correct answer: Triceps brachii. Clinical: Preserved triceps function rules out musculocutaneous injury.
Keyword Definitions
• Axillary nerve – Branch of posterior cord of brachial plexus, supplies deltoid and teres minor.
• Quadrangular space – Anatomical space transmitting axillary nerve and posterior circumflex humeral artery.
• Deltoid paralysis – Clinical feature of axillary nerve injury, causing loss of shoulder abduction.
• Humeral surgical neck – Common fracture site leading to axillary nerve damage.
• Circumflex humeral arteries – Branches of axillary artery encircling humerus.
• Teres minor – Rotator cuff muscle innervated by axillary nerve.
• Shoulder dislocation – Can injure axillary nerve.
• Posterior circumflex humeral artery – Runs with axillary nerve in quadrangular space.
• Clinical test – Abduction and sensation over regimental badge area for axillary nerve integrity.
• Brachial plexus – Nerve network supplying upper limb.
• Surgical relevance – Axillary nerve at risk during deltoid intramuscular injections.
Chapter: Anatomy / Upper Limb
Topic: Brachial Plexus
Subtopic: Axillary Nerve and Vessels
Lead Question – 2013
Axillary nerve is accompanied by which artery?
a) Axillary
b) Subscapular
c) Anterior circumflex humeral
d) Posterior circumflex humeral
Explanation: Axillary nerve passes through the quadrangular space along with the posterior circumflex humeral artery. This anatomical relationship is clinically important during humeral neck fractures or shoulder dislocations. Correct answer: (d) Posterior circumflex humeral artery. Clinical: Injury leads to deltoid weakness and sensory loss over regimental badge area.
Guessed Questions for NEET PG
1) Which space transmits axillary nerve and posterior circumflex humeral artery?
a) Triangular space
b) Quadrangular space
c) Cubital fossa
d) Axilla
Explanation: Axillary nerve and posterior circumflex humeral artery pass through quadrangular space. Correct answer: Quadrangular space. Clinical: Compression here can cause axillary neuropathy.
2) Fracture of surgical neck of humerus most likely injures?
a) Radial nerve
b) Axillary nerve
c) Median nerve
d) Ulnar nerve
Explanation: Surgical neck fracture endangers axillary nerve and posterior circumflex humeral artery. Correct answer: Axillary nerve. Clinical: Presents with deltoid atrophy and shoulder abduction weakness.
3) Which muscle is NOT supplied by axillary nerve?
a) Deltoid
b) Teres minor
c) Teres major
d) Skin over regimental badge
Explanation: Teres major is supplied by subscapular nerve, not axillary nerve. Correct answer: Teres major. Clinical: Differentiates axillary nerve palsy from broader plexus injury.
4) Loss of sensation over regimental badge area indicates injury to?
a) Radial nerve
b) Axillary nerve
c) Suprascapular nerve
d) Musculocutaneous nerve
Explanation: Axillary nerve injury causes sensory deficit over regimental badge area. Correct answer: Axillary nerve. Clinical: Pathognomonic for axillary neuropathy.
5) Which rotator cuff muscle is innervated by axillary nerve?
a) Supraspinatus
b) Infraspinatus
c) Teres minor
d) Subscapularis
Explanation: Teres minor is the only rotator cuff muscle supplied by axillary nerve. Correct answer: Teres minor. Clinical: Weakness in external rotation occurs in axillary nerve injury.
6) During deltoid intramuscular injection, which nerve is at risk?
a) Radial nerve
b) Median nerve
c) Axillary nerve
d) Musculocutaneous nerve
Explanation: Axillary nerve runs deep to deltoid; incorrect needle placement may injure it. Correct answer: Axillary nerve. Clinical: Presents with deltoid weakness.
7) Posterior circumflex humeral artery is a branch of?
a) Brachial artery
b) Axillary artery
c) Subclavian artery
d) Radial artery
Explanation: Posterior circumflex humeral artery arises from the 3rd part of axillary artery. Correct answer: Axillary artery. Clinical: Injured in humeral neck fractures.
8) Which movement is most affected in axillary nerve injury?
a) Elbow flexion
b) Shoulder abduction
c) Wrist extension
d) Thumb opposition
Explanation: Deltoid paralysis impairs shoulder abduction beyond 15 degrees. Correct answer: Shoulder abduction. Clinical: Differentiates from supraspinatus injury which initiates abduction.
9) Which clinical test best evaluates axillary nerve function?
a) Flexion of elbow
b) Abduction of shoulder against resistance
c) Extension of wrist
d) Pronation of forearm
Explanation: Abduction of shoulder against resistance tests deltoid function supplied by axillary nerve. Correct answer: Shoulder abduction against resistance. Clinical: Standard examination method.
10) Anterior dislocation of shoulder commonly injures?
a) Radial nerve
b) Axillary nerve
c) Median nerve
d) Ulnar nerve
Explanation: Axillary nerve lies close to shoulder joint and is frequently injured in anterior dislocation. Correct answer: Axillary nerve. Clinical: Presents with deltoid atrophy and regimental badge anesthesia.
Keyword Definitions
• Dual nerve supply – Muscle receiving motor innervation from two different nerves.
• Subscapularis – Supplied by upper and lower subscapular nerves.
• Pectoralis major – Supplied by medial and lateral pectoral nerves.
• Pronator teres – Supplied by median nerve only.
• Flexor digitorum profundus – Medial half by ulnar nerve, lateral half by anterior interosseous branch of median nerve.
• Brachial plexus – Network of nerves supplying upper limb, roots C5–T1.
• Median nerve – Formed by medial and lateral cords, supplies most forearm flexors.
• Ulnar nerve – Arises from medial cord, supplies intrinsic hand muscles and medial FDP.
• Subscapular nerves – Branches of posterior cord, innervate subscapularis.
• Clinical correlation – Knowledge of dual supply important in nerve lesions and recovery.
• Muscle palsy – Weakness pattern helps localize lesion to specific nerve or part of plexus.
Chapter: Anatomy / Upper Limb
Topic: Brachial Plexus and Muscle Innervation
Subtopic: Dual nerve supply of upper limb muscles
Lead Question – 2013
All of the following muscles have dual nerve supply except?
a) Subscapularis
b) Pectoralis major
c) Pronator teres
d) Flexor digitorum profundus
Explanation: Subscapularis has dual supply (upper and lower subscapular nerves). Pectoralis major has dual supply (medial and lateral pectoral nerves). FDP has dual supply (median and ulnar nerves). Pronator teres has single supply (median nerve). Correct answer: (c) Pronator teres. Clinical: Isolated median injury can paralyze pronator teres completely.
Guessed Questions for NEET PG
1) Which muscle among the following is supplied by both ulnar and median nerves?
a) Flexor pollicis longus
b) Flexor carpi radialis
c) Flexor digitorum profundus
d) Pronator quadratus
Explanation: Flexor digitorum profundus has dual supply – medial half by ulnar, lateral half by anterior interosseous (median). Correct answer: FDP. Clinical: Explains partial preservation in isolated lesions.
2) Subscapularis is supplied by?
a) Upper and lower subscapular nerves
b) Thoracodorsal nerve
c) Lateral pectoral nerve
d) Axillary nerve
Explanation: Subscapularis is innervated by both upper and lower subscapular nerves from posterior cord. Correct answer: Upper and lower subscapular nerves. Clinical: Injury leads to weak internal rotation.
3) Which muscle receives innervation from both medial and lateral pectoral nerves?
a) Pectoralis major
b) Pectoralis minor
c) Subclavius
d) Serratus anterior
Explanation: Pectoralis major is supplied by medial and lateral pectoral nerves. Correct answer: Pectoralis major. Clinical: Paralysis leads to weak adduction and internal rotation.
4) A patient with ulnar nerve lesion at wrist retains partial flexion of DIP of ring finger due to?
a) Median nerve supply
b) Radial nerve supply
c) Musculocutaneous nerve supply
d) Axillary nerve supply
Explanation: Lateral half of FDP (index and middle fingers) supplied by median, medial half (ring and little fingers) by ulnar. Correct answer: Median nerve supply. Clinical: Explains incomplete loss in ulnar palsy.
5) Which of the following has single nerve supply?
a) FDP
b) Pectoralis major
c) Pronator teres
d) Subscapularis
Explanation: Pronator teres is solely supplied by median nerve. Others have dual innervation. Correct answer: Pronator teres. Clinical: Useful in lesion localization.
6) Which nerve supplies medial half of flexor digitorum profundus?
a) Ulnar
b) Median
c) Radial
d) Musculocutaneous
Explanation: Medial half (ring and little fingers) of FDP is innervated by ulnar nerve. Correct answer: Ulnar nerve. Clinical: Explains weakness of DIP flexion in ulnar palsy.
7) Damage to lateral pectoral nerve causes weakness in?
a) Shoulder abduction
b) Arm adduction
c) Elbow flexion
d) Wrist extension
Explanation: Lateral pectoral nerve innervates pectoralis major, main action is adduction and internal rotation of arm. Correct answer: Arm adduction. Clinical: Loss of powerful adduction in lesion.
8) A patient with lesion of posterior cord affecting both upper and lower subscapular nerves shows weakness in?
a) Internal rotation
b) External rotation
c) Abduction
d) Supination
Explanation: Subscapularis performs internal rotation of humerus, supplied by both upper and lower subscapular nerves. Correct answer: Internal rotation. Clinical: Shoulder stability is also reduced.
9) Median nerve injury at elbow spares which of the following?
a) Pronator teres
b) Flexor digitorum profundus (medial half)
c) Flexor digitorum superficialis
d) Flexor pollicis longus
Explanation: Medial half of FDP is supplied by ulnar nerve, hence spared in median nerve injury at elbow. Correct answer: FDP (medial half). Clinical: Explains partial preservation of finger flexion.
10) Which of the following combinations represent dual innervation correctly?
a) FDP – Median & Ulnar
b) Pectoralis major – Medial & Lateral pectoral
c) Subscapularis – Upper & Lower subscapular
d) All of the above
Explanation: All mentioned muscles are examples of dual innervation. Correct answer: All of the above. Clinical: Important for understanding muscle function in partial nerve injuries.
Keyword Definitions
• Profunda brachii artery – Deep artery of arm, branch of brachial artery, runs in spiral groove.
• Spiral groove – Shallow groove on posterior humerus, occupied by radial nerve and profunda brachii artery.
• Radial nerve – Continuation of posterior cord of brachial plexus, supplies extensor compartment.
• Ulnar nerve – Arises from medial cord, passes behind medial epicondyle, supplies intrinsic hand muscles.
• Median nerve – Formed from medial and lateral cords, passes through carpal tunnel, major flexor nerve.
• Humeral shaft fracture – Common injury damaging radial nerve in spiral groove.
• Wrist drop – Clinical sign of radial nerve injury, due to loss of extensor muscle function.
• Saturday night palsy – Radial nerve compression neuropathy in spiral groove.
• Deep brachial artery – Synonym for profunda brachii artery, accompanies radial nerve.
• Extensor compartment – Muscles of posterior arm and forearm controlled by radial nerve.
• Clinical correlation – Spiral groove relation important in fractures and compressive neuropathies.
Chapter: Anatomy / Upper Limb
Topic: Arm and Brachial Plexus
Subtopic: Radial nerve and profunda brachii artery in spiral groove
Lead Question – 2013
Nerve running along with profunda brachii artery, in spiral groove?
a) Ulnar
b) Median
c) Radial
d) None
Explanation: The radial nerve runs along with the profunda brachii artery in the spiral groove of the humerus. This relationship is clinically significant as humeral shaft fractures can injure both structures. Correct answer: (c) Radial. Clinical: Injury causes wrist drop and sensory loss over dorsum of hand.
Guessed Questions for NEET PG
1) A mid-shaft fracture of humerus most commonly injures?
a) Median nerve
b) Radial nerve
c) Ulnar nerve
d) Musculocutaneous nerve
Explanation: Mid-shaft humeral fractures frequently damage the radial nerve as it lies in the spiral groove. Correct answer: Radial nerve. Clinical: Presents with wrist drop and loss of finger extension.
2) Which muscle is first affected in radial nerve palsy at spiral groove?
a) Triceps
b) Anconeus
c) Brachioradialis
d) Extensor carpi radialis longus
Explanation: Triceps is spared in spiral groove lesions. Brachioradialis and wrist extensors are first affected. Correct answer: Brachioradialis. Clinical: Weak elbow flexion in mid-pronation position.
3) Saturday night palsy refers to?
a) Ulnar nerve compression
b) Radial nerve compression
c) Median nerve compression
d) Axillary nerve compression
Explanation: Saturday night palsy occurs when prolonged compression damages the radial nerve in spiral groove during deep sleep or intoxication. Correct answer: Radial nerve compression. Clinical: Wrist drop with sensory loss.
4) Sensory loss in radial nerve injury at spiral groove involves?
a) Thenar eminence
b) Dorsum of first web space
c) Medial forearm
d) Palmar little finger
Explanation: Spiral groove injury spares triceps but causes sensory loss over dorsum of hand, particularly first web space. Correct answer: Dorsum of first web space. Clinical: Important diagnostic clue.
5) Which branch of radial nerve supplies triceps?
a) Posterior cutaneous nerve
b) Muscular branches
c) Deep branch
d) Superficial branch
Explanation: Muscular branches of radial nerve supply triceps before entering spiral groove. Correct answer: Muscular branches. Clinical: Triceps preserved in spiral groove lesions.
6) Which artery is at risk with humeral shaft fracture along with radial nerve?
a) Brachial artery
b) Profunda brachii artery
c) Radial artery
d) Ulnar artery
Explanation: Profunda brachii artery accompanies radial nerve in spiral groove, making it vulnerable in shaft fractures. Correct answer: Profunda brachii artery. Clinical: Bleeding complicates fracture management.
7) Which test best detects radial nerve palsy?
a) Asking patient to oppose thumb
b) Asking patient to extend wrist
c) Asking patient to flex DIP of index
d) Asking patient to abduct little finger
Explanation: Wrist extension is controlled by radial nerve. In palsy, patient cannot extend wrist, producing wrist drop. Correct answer: Wrist extension test. Clinical: Pathognomonic finding.
8) Wrist drop occurs due to paralysis of?
a) Flexor muscles
b) Extensor muscles
c) Pronator muscles
d) Intrinsic hand muscles
Explanation: Radial nerve injury paralyzes extensor muscles of forearm, causing wrist drop. Correct answer: Extensor muscles. Clinical: Patient presents with inability to extend wrist and fingers.
9) Which part of triceps is usually spared in spiral groove lesion?
a) Long head
b) Lateral head
c) Medial head
d) All heads affected
Explanation: Radial nerve supplies long and lateral heads of triceps before entering spiral groove, hence spared. Medial head may be affected. Correct answer: Long and lateral heads spared. Clinical: Partial triceps weakness only.
10) In radial nerve injury, supination is preserved due to action of?
a) Biceps brachii
b) Supinator
c) Pronator teres
d) Brachialis
Explanation: Supination is performed by supinator (radial nerve) and biceps brachii (musculocutaneous nerve). Even if radial nerve is injured, biceps maintains supination. Correct answer: Biceps brachii. Clinical: Supination relatively preserved in palsy.
Keyword Definitions
• Anatomical snuff box – Triangular depression on lateral wrist, important surface landmark.
• Abductor pollicis longus (APL) – Forms lateral boundary of snuff box.
• Extensor pollicis brevis (EPB) – Lateral boundary with APL.
• Extensor pollicis longus (EPL) – Forms medial boundary.
• Extensor carpi ulnaris (ECU) – Not a boundary of snuff box, lies more medially.
• Radial artery – Runs through floor of snuff box, pulse palpable.
• Scaphoid bone – Floor of snuff box, common fracture site.
• Cephalic vein – Originates near snuff box region.
• Superficial branch of radial nerve – Crosses over snuff box, provides cutaneous innervation.
• Clinical importance – Site for palpating scaphoid fracture tenderness.
• Wrist injuries – Tenderness in snuff box suggests scaphoid fracture.
Chapter: Anatomy / Upper Limb
Topic: Wrist and Hand
Subtopic: Anatomical snuff box and relations
Lead Question – 2013
Boundaries of anatomical snuff box are all except
a) APL
b) EPL
c) EPB
d) ECU
Explanation: The anatomical snuff box is bounded laterally by abductor pollicis longus and extensor pollicis brevis, medially by extensor pollicis longus. Extensor carpi ulnaris is not a boundary. Correct answer: (d) ECU. Clinical: Snuff box tenderness is diagnostic of scaphoid fracture.
Guessed Questions for NEET PG
1) Which structure forms the floor of anatomical snuff box?
a) Capitate
b) Lunate
c) Scaphoid
d) Pisiform
Explanation: The scaphoid forms the main floor of the anatomical snuff box, along with trapezium. Correct answer: Scaphoid. Clinical: Scaphoid fractures are suspected if snuff box tenderness is present after a fall on an outstretched hand.
2) Which artery passes through anatomical snuff box?
a) Ulnar artery
b) Radial artery
c) Brachial artery
d) Interosseous artery
Explanation: The radial artery runs through the floor of the snuff box before entering the palm. Correct answer: Radial artery. Clinical: Radial pulse can be palpated here in lean individuals.
3) Injury to scaphoid bone presents with?
a) Swelling of thenar eminence
b) Pain in anatomical snuff box
c) Loss of thumb extension
d) Tingling of little finger
Explanation: Scaphoid fracture commonly presents with pain and tenderness in anatomical snuff box. Correct answer: Pain in anatomical snuff box. Clinical: Delayed diagnosis risks avascular necrosis of proximal scaphoid.
4) Which tendon crosses the floor of snuff box?
a) Flexor carpi radialis
b) Extensor carpi radialis longus
c) Palmaris longus
d) Flexor digitorum profundus
Explanation: Extensor carpi radialis longus and brevis tendons form part of floor of anatomical snuff box. Correct answer: Extensor carpi radialis longus. Clinical: Palpable tendon aids in anatomical landmarking.
5) Which nerve crosses superficial to anatomical snuff box?
a) Ulnar nerve
b) Median nerve
c) Superficial radial nerve
d) Deep radial nerve
Explanation: The superficial branch of radial nerve crosses superficial to snuff box, supplying cutaneous sensation. Correct answer: Superficial radial nerve. Clinical: Injury causes numbness over dorsum of hand near thumb.
6) Which muscle tendon forms medial boundary of snuff box?
a) EPL
b) EPB
c) APL
d) ECU
Explanation: The medial boundary of the snuff box is formed by extensor pollicis longus tendon. Correct answer: EPL. Clinical: Prominent during thumb extension testing.
7) A patient with fall on outstretched hand and tenderness in snuff box most likely has?
a) Colles fracture
b) Scaphoid fracture
c) Hamate fracture
d) Lunate dislocation
Explanation: Snuff box tenderness is classic for scaphoid fracture. Correct answer: Scaphoid fracture. Clinical: Requires urgent immobilization to prevent avascular necrosis.
8) Which carpal bone is most prone to avascular necrosis after fracture?
a) Lunate
b) Pisiform
c) Scaphoid
d) Capitate
Explanation: The scaphoid bone is prone to avascular necrosis due to retrograde blood supply. Correct answer: Scaphoid. Clinical: Missed fractures can cause chronic wrist pain.
9) In wrist examination, tenderness in anatomical snuff box is tested to rule out?
a) Radial head fracture
b) Scaphoid fracture
c) Ulna styloid fracture
d) Capitate fracture
Explanation: Snuff box tenderness specifically indicates scaphoid fracture. Correct answer: Scaphoid fracture. Clinical: Common in young adults after fall on outstretched hand.
10) Which vein originates near anatomical snuff box?
a) Basilic vein
b) Cephalic vein
c) Median cubital vein
d) Radial vein
Explanation: The cephalic vein begins from venous plexus near the anatomical snuff box. Correct answer: Cephalic vein. Clinical: Important for venous access in upper limb procedures.
Keyword Definitions
• Median nerve – Major nerve of forearm and hand, supplies palmar aspect of lateral 3½ fingers.
• Ulnar nerve – Supplies medial 1½ fingers and most intrinsic hand muscles.
• Radial nerve – Provides sensation to dorsum of hand and motor supply to extensor compartment.
• Digital nerves – Terminal branches of median and ulnar nerves, supplying fingers and nail beds.
• Nail bed – Specialized skin beneath nail plate, richly innervated for fine sensation.
• Palmar digital branches – Arise from median nerve, innervate palmar surfaces of lateral fingers.
• Dorsal digital branches – Arise from radial and ulnar nerves, supply dorsum of fingers.
• Clinical surface anatomy – Nail bed sensation is a key test in digital nerve injuries.
• Carpal tunnel – Narrow passage in wrist transmitting median nerve and tendons, site of compression.
• Sensory testing – Performed with pinprick or light touch to assess nerve integrity in trauma.
• Hand dominance – Important in recovery and surgical repair of nerve injuries.
Chapter: Anatomy / Upper Limb
Topic: Hand
Subtopic: Nerve supply of digits and nail bed
Lead Question – 2013
The nerve supply of nail bed of index finger is?
a) Superficial br of radial nerve
b) Deep br of radial nerve
c) Median nerve
d) Ulnar nerve
Explanation: The nail bed of index finger is supplied by the palmar digital branches of the median nerve. The superficial branch of radial nerve supplies dorsum of hand but not the nail bed of index. Correct answer: (c) Median nerve. Clinical: Sensory loss here suggests median nerve injury.
Guessed Questions for NEET PG
1) Sensory loss over nail bed of middle finger indicates injury to?
a) Ulnar nerve
b) Median nerve
c) Radial nerve
d) Musculocutaneous nerve
Explanation: The nail bed of middle finger, like index, is innervated by the median nerve. Injury to the nerve proximal to wrist causes loss of sensation here. Correct answer: Median nerve. Clinical: Important in diagnosing carpal tunnel syndrome.
2) Which nerve supplies nail bed of little finger?
a) Radial nerve
b) Median nerve
c) Ulnar nerve
d) Musculocutaneous nerve
Explanation: The little finger is supplied by the palmar digital branches of the ulnar nerve. Correct answer: Ulnar nerve. Clinical: Injury to ulnar nerve in Guyon’s canal affects sensation of little finger.
3) Which nerve injury is suspected when thumb, index, and middle finger nail beds lose sensation?
a) Radial nerve
b) Median nerve
c) Ulnar nerve
d) Axillary nerve
Explanation: Loss of sensation in thumb, index, and middle finger nail beds indicates median nerve injury. Correct answer: Median nerve. Clinical: Often seen in carpal tunnel syndrome and supracondylar fractures.
4) The superficial branch of radial nerve supplies?
a) Palmar surface of index finger
b) Dorsum of thumb
c) Nail bed of index finger
d) Palmaris brevis muscle
Explanation: The superficial branch of radial nerve supplies dorsum of thumb and hand but does not reach nail beds of index finger. Correct answer: Dorsum of thumb. Clinical: Injury leads to sensory deficit in dorsum of hand.
5) Injury at wrist producing loss of sensation in nail bed of ring finger (lateral half) indicates?
a) Ulnar nerve
b) Median nerve
c) Radial nerve
d) Posterior interosseous nerve
Explanation: The lateral half of ring finger is supplied by median nerve digital branches. Correct answer: Median nerve. Clinical: Important in mixed finger innervation assessment.
6) Which nerve supplies motor innervation to thenar muscles along with nail bed sensation of index finger?
a) Ulnar nerve
b) Median nerve
c) Radial nerve
d) Axillary nerve
Explanation: The median nerve supplies both thenar muscles (except adductor pollicis and deep head of FPB) and sensation of index finger nail bed. Correct answer: Median nerve. Clinical: Injury causes thenar atrophy and sensory loss.
7) A patient with carpal tunnel syndrome will typically complain of numbness over?
a) Little finger nail bed
b) Index and middle finger nail beds
c) Medial palm
d) Dorsum of hand
Explanation: Carpal tunnel compression of median nerve affects sensation over nail beds of thumb, index, middle, and radial half of ring finger. Correct answer: Index and middle finger nail beds. Clinical: Classic diagnostic sign.
8) Which nerve injury is tested by checking sensation at tip of little finger?
a) Median nerve
b) Radial nerve
c) Ulnar nerve
d) Axillary nerve
Explanation: Sensation at tip of little finger is supplied by ulnar nerve digital branches. Correct answer: Ulnar nerve. Clinical: Simple bedside test to isolate ulnar nerve damage.
9) Which nerve provides sensory supply to dorsum of index finger proximal phalanx?
a) Ulnar nerve
b) Median nerve
c) Superficial radial nerve
d) Musculocutaneous nerve
Explanation: The dorsum of proximal index finger is supplied by superficial branch of radial nerve. Correct answer: Superficial radial nerve. Clinical: Differentiate radial vs median injury.
10) Following supracondylar fracture, patient develops loss of sensation in nail bed of index finger. Which nerve is likely injured?
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Musculocutaneous nerve
Explanation: Supracondylar fracture often injures median nerve, causing sensory loss in index nail bed. Correct answer: Median nerve. Clinical: Needs urgent assessment due to risk of Volkmann’s ischemic contracture.
Keyword Definitions
• Ulnar nerve – Terminal branch of medial cord of brachial plexus, supplies intrinsic hand muscles and some forearm flexors.
• Flexor carpi ulnaris (FCU) – Forearm muscle, flexes and adducts wrist, supplied by ulnar nerve.
• Flexor digitorum profundus (FDP) – Deep flexor of fingers, medial half supplied by ulnar nerve, lateral half by median nerve.
• Forearm flexors – Muscles anterior to radius/ulna, flex wrist and fingers.
• Medial cord – Branch of brachial plexus giving rise to ulnar nerve.
• Cubital tunnel – Anatomical passage for ulnar nerve at elbow, common entrapment site.
• Claw hand – Deformity caused by ulnar nerve injury, hyperextension at MCP, flexion at IP joints.
• Guyon’s canal – Ulnar nerve compression site at wrist.
• Sensory supply – Ulnar nerve supplies medial 1½ fingers and corresponding palm/dorsum.
• Motor supply – Ulnar nerve supplies FCU, medial FDP, and most intrinsic hand muscles.
• Clinical localization – Identifying site of nerve injury based on selective muscle/sensory involvement.
Chapter: Anatomy / Upper Limb
Topic: Brachial Plexus
Subtopic: Ulnar Nerve in Arm and Forearm
Lead Question – 2013
In arm ulnar nerve gives muscular branch to which muscle ?
a) FCU
b) FDP
c) Both
d) None
Explanation: In the arm, the ulnar nerve does not supply any muscle. It simply travels down medially without branches. FCU and FDP receive branches in the forearm, not arm. Correct answer: None. Clinical: important in localizing lesions since proximal arm injuries do not affect muscle action directly.
Guessed Questions for NEET PG
1) Which muscle is supplied by ulnar nerve in the forearm?
a) Pronator teres
b) Flexor carpi ulnaris
c) Flexor pollicis longus
d) Palmaris longus
Explanation: Ulnar nerve supplies FCU and medial half of FDP in the forearm. Flexor carpi ulnaris is a key muscle supplied by it. Correct answer: Flexor carpi ulnaris. Clinical: tested by resisted wrist flexion and adduction.
2) A patient with ulnar nerve lesion at elbow will have weakness of:
a) Pronation
b) Wrist flexion and adduction
c) Wrist extension
d) Supination
Explanation: Elbow lesion of ulnar nerve affects FCU and medial FDP. This weakens wrist flexion/adduction and finger flexion. Correct answer: Wrist flexion and adduction. Clinical: combined with sensory loss over medial hand.
3) Which deformity is caused by distal ulnar nerve lesion at wrist?
a) Wrist drop
b) Claw hand
c) Ape thumb
d) Benediction sign
Explanation: Distal ulnar nerve lesion causes paralysis of lumbricals/interossei leading to claw hand deformity. Correct answer: Claw hand. Clinical: more severe when lesion is distal because FDP is spared.
4) Which nerve is compressed in Guyon’s canal syndrome?
a) Radial
b) Median
c) Ulnar
d) Musculocutaneous
Explanation: Ulnar nerve passes through Guyon’s canal near wrist. Compression here produces sensory and motor loss in ulnar distribution without affecting forearm muscles. Correct answer: Ulnar nerve. Clinical: common in cyclists ("handlebar palsy").
5) Which intrinsic hand muscle is not supplied by ulnar nerve?
a) Adductor pollicis
b) First dorsal interosseous
c) Lateral two lumbricals
d) Palmar interossei
Explanation: Median nerve supplies lateral two lumbricals and thenar muscles (except adductor pollicis). Ulnar supplies all others. Correct answer: Lateral two lumbricals. Clinical: important for fine finger movements.
6) Injury to ulnar nerve at elbow spares which muscle?
a) FCU
b) FDP (medial half)
c) FDP (lateral half)
d) Palmar interossei
Explanation: Lateral half of FDP is supplied by median nerve, not ulnar nerve. Hence spared in elbow lesion. Correct answer: FDP (lateral half). Clinical: helps differentiate median vs ulnar nerve contributions.
7) Sensory supply of ulnar nerve includes:
a) Lateral 3½ fingers
b) Medial 1½ fingers
c) Entire palm
d) Thenar eminence
Explanation: Ulnar nerve supplies skin of medial 1½ fingers and adjacent palm/dorsum. Correct answer: Medial 1½ fingers. Clinical: loss of sensation here is diagnostic.
8) Froment’s sign is positive in lesion of:
a) Radial nerve
b) Median nerve
c) Ulnar nerve
d) Axillary nerve
Explanation: Froment’s sign indicates weakness of adductor pollicis supplied by ulnar nerve. Thumb flexion occurs due to compensation by flexor pollicis longus. Correct answer: Ulnar nerve. Clinical: classic bedside test.
9) A patient with difficulty in finger abduction most likely has injury to:
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Musculocutaneous nerve
Explanation: Interossei supplied by ulnar nerve abduct/adduct fingers. Injury impairs abduction. Correct answer: Ulnar nerve. Clinical: seen in claw hand cases.
10) Which test checks for integrity of ulnar nerve?
a) Phalen’s test
b) Card test
c) Tinel’s sign
d) O’Brien’s test
Explanation: Card test involves holding paper between fingers using interossei. Ulnar nerve lesion causes inability to hold paper. Correct answer: Card test. Clinical: simple bedside diagnostic tool.
Keyword Definitions
• Radial nerve – Largest branch of brachial plexus, supplies posterior compartment of arm and forearm.
• Spiral groove – Groove on humerus where radial nerve travels, common injury site in fractures.
• Triceps brachii – Muscle with three heads (long, lateral, medial), main extensor of elbow.
• Extensor carpi radialis longus (ECRL) – Radial nerve branch above spiral groove, extends wrist.
• Wrist drop – Inability to extend wrist due to radial nerve lesion.
• Posterior interosseous nerve – Deep radial branch, supplies finger extensors.
• Saturday night palsy – Radial nerve compression in axilla leading to wrist drop.
• Humeral shaft fracture – Common cause of radial nerve injury at spiral groove.
• Supinator canal – Site of posterior interosseous nerve entrapment.
• Clinical localization – Identifying nerve injury by selective motor/sensory loss.
• Dorsal web space – Sensory area supplied by superficial radial nerve.
Chapter: Anatomy / Upper Limb
Topic: Brachial Plexus
Subtopic: Radial Nerve at Spiral Groove
Lead Question – 2013
Which muscle will be paralyzed when radial nerve is injured in just below the spiral groove ?
a) Lateral head of triceps
b) Medial head of triceps
c) Long head of triceps
d) ECRL
Explanation: Radial nerve gives branches to triceps before entering spiral groove, sparing it in distal lesions. ECRL is also supplied above the groove. Injury just below spiral groove paralyzes medial head of triceps. Correct answer: Medial head of triceps. Clinical: elbow extension weak but not absent.
Guessed Questions for NEET PG
1) In a mid-shaft humeral fracture, which motor deficit is most expected?
a) Loss of elbow extension
b) Wrist drop
c) Loss of pronation
d) Finger flexion weakness
Explanation: Radial nerve in spiral groove is injured, sparing triceps but affecting wrist/finger extensors. This causes wrist drop while elbow extension remains intact. Correct answer: Wrist drop. Clinical: selective extensor weakness helps localize lesion.
2) A patient with radial nerve injury in axilla will present with:
a) Wrist drop only
b) Elbow and wrist extension loss
c) Only sensory loss
d) Finger abduction loss
Explanation: Axillary radial nerve lesion affects triceps, wrist extensors, and sensory branches. This produces loss of elbow and wrist extension with sensory loss. Correct answer: Elbow and wrist extension loss. Clinical: classic in crutch palsy.
3) Which muscle is spared in radial nerve injury at spiral groove?
a) Extensor digitorum
b) Extensor carpi radialis longus
c) Extensor pollicis longus
d) Extensor indicis
Explanation: ECRL is supplied before spiral groove. Thus, wrist extension is weak but not lost. Correct answer: Extensor carpi radialis longus. Clinical: partial wrist drop seen instead of complete.
4) Loss of thumb extension is seen in injury to:
a) Median nerve
b) Ulnar nerve
c) Posterior interosseous nerve
d) Musculocutaneous nerve
Explanation: Posterior interosseous nerve supplies extensor pollicis longus and brevis. Its injury causes inability to extend thumb. Correct answer: Posterior interosseous nerve. Clinical: selective thumb drop without wrist involvement.
5) A patient cannot adduct fingers but wrist extension is normal. Likely nerve injured?
a) Radial
b) Median
c) Ulnar
d) Axillary
Explanation: Ulnar nerve supplies interossei for finger adduction. Radial nerve intact preserves wrist extension. Correct answer: Ulnar nerve. Clinical: card test positive.
6) Injury to radial nerve just above wrist affects:
a) Motor only
b) Sensory only
c) Both motor and sensory
d) Neither
Explanation: At wrist, radial nerve is superficial and purely sensory. Injury here causes sensory loss in dorsum of first web space. Correct answer: Sensory only. Clinical: no motor deficit seen.
7) Which nerve is tested by sensation over dorsal first web space?
a) Median
b) Ulnar
c) Radial
d) Musculocutaneous
Explanation: Radial nerve superficial branch supplies skin of first web space dorsally. Correct answer: Radial nerve. Clinical: useful in localizing high radial lesions.
8) Which nerve injury produces “claw hand”?
a) Median
b) Ulnar
c) Radial
d) Axillary
Explanation: Ulnar nerve injury at wrist causes paralysis of medial lumbricals leading to claw hand deformity. Correct answer: Ulnar nerve. Clinical: worsens with distal lesions.
9) Inability to supinate forearm after fracture of proximal radius is due to injury of:
a) Median
b) Radial
c) Musculocutaneous
d) Ulnar
Explanation: Supinator is innervated by posterior interosseous nerve, branch of radial. Injury near proximal radius affects supination. Correct answer: Radial nerve. Clinical: partial supination possible via biceps if intact.
10) A patient develops wrist drop after sleeping with arm compressed over chair. This condition is called:
a) Crutch palsy
b) Saturday night palsy
c) Honeymoon palsy
d) Arcade syndrome
Explanation: Compression of radial nerve in axilla during deep sleep causes Saturday night palsy. Correct answer: Saturday night palsy. Clinical: wrist drop with sensory loss over dorsum hand.
Keyword Definitions
• Radial nerve – Largest branch of brachial plexus, supplies extensors of arm and forearm.
• Posterior interosseous nerve – Deep terminal branch of radial nerve, supplies finger extensors.
• Median nerve – Supplies most anterior forearm muscles and thenar muscles.
• Ulnar nerve – Supplies intrinsic hand muscles and medial forearm muscles.
• Wrist drop – Inability to extend wrist due to radial nerve injury.
• Spiral groove – Location of radial nerve on humerus, commonly injured in fractures.
• Crutch palsy – Radial nerve injury due to axillary compression from crutches.
• Dorsal digital branch – Radial nerve branch supplying skin over first web space.
• Clinical localization – Identifying nerve injuries based on motor and sensory deficits.
• Supinator canal – Site where posterior interosseous nerve may be compressed.
• Extensor compartment – Posterior muscles of forearm responsible for finger/wrist extension.
Chapter: Anatomy / Upper Limb
Topic: Brachial Plexus
Subtopic: Posterior Interosseous Nerve
Lead Question – 2013
A person had injury to right upper limb he is not able to extend fingers but able to extend wrist and elbow. Nerve injured is ?
a) Radial
b) Median
c) Ulnar
d) Posterior interosseous
Explanation: Finger extension is controlled by posterior interosseous nerve, a branch of radial nerve. Wrist and elbow extension are preserved because proximal radial nerve branches are intact. Correct answer: Posterior interosseous nerve. Clinical: injury produces finger drop without wrist drop.
Guessed Questions for NEET PG
1) Which nerve is injured in humeral shaft fracture leading to wrist drop?
a) Median
b) Radial
c) Ulnar
d) Axillary
Explanation: Radial nerve travels in the spiral groove of humerus and is vulnerable in shaft fractures. Injury leads to wrist drop and sensory loss in dorsum of hand. Correct answer: Radial nerve. Clinical: triceps often spared due to proximal innervation.
2) A patient with wrist extension preserved but inability to extend thumb likely has lesion of:
a) Median nerve
b) Radial nerve
c) Posterior interosseous nerve
d) Ulnar nerve
Explanation: Posterior interosseous nerve specifically supplies thumb extensors. Wrist extension is preserved via intact extensor carpi radialis longus. Correct answer: Posterior interosseous nerve. Clinical: selective finger drop is hallmark.
3) Inability to oppose thumb is due to injury of:
a) Ulnar nerve
b) Median nerve
c) Radial nerve
d) Musculocutaneous nerve
Explanation: Median nerve supplies thenar muscles including opponens pollicis. Its injury prevents thumb opposition. Correct answer: Median nerve. Clinical: seen in carpal tunnel syndrome or wrist lacerations.
4) Which nerve is injured in “Saturday night palsy”?
a) Radial
b) Ulnar
c) Median
d) Axillary
Explanation: Prolonged pressure in axilla compresses radial nerve, leading to wrist drop. Correct answer: Radial nerve. Clinical: common in unconscious patients with arm hanging over chair.
5) Loss of sensation in first dorsal web space occurs in:
a) Median nerve lesion
b) Ulnar nerve lesion
c) Radial nerve lesion
d) Axillary nerve lesion
Explanation: The radial nerve supplies skin over dorsum of first web space. Correct answer: Radial nerve. Clinical: this sensory loss confirms radial nerve lesion.
6) Which nerve passes through supinator canal and may be compressed there?
a) Ulnar
b) Median
c) Posterior interosseous
d) Axillary
Explanation: Posterior interosseous nerve passes through supinator canal (Arcade of Frohse) where entrapment can occur. Correct answer: Posterior interosseous nerve. Clinical: presents with finger drop but preserved wrist extension.
7) A patient cannot extend elbow. The nerve involved is:
a) Median
b) Radial
c) Ulnar
d) Musculocutaneous
Explanation: Radial nerve supplies triceps brachii responsible for elbow extension. Injury proximal to triceps branches leads to loss of elbow extension. Correct answer: Radial nerve.
8) Inability to adduct fingers is due to lesion of:
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Axillary nerve
Explanation: Ulnar nerve supplies interossei muscles responsible for finger adduction and abduction. Correct answer: Ulnar nerve. Clinical: test by asking patient to hold a card between fingers (card test).
9) Which nerve is commonly injured during axillary lymph node dissection?
a) Long thoracic
b) Radial
c) Axillary
d) Median
Explanation: Long thoracic and thoracodorsal nerves are at risk, but not radial. Correct answer: Long thoracic nerve. Clinical: its injury leads to winging of scapula due to serratus anterior paralysis.
10) A patient with inability to pronate forearm likely has injury of:
a) Radial nerve
b) Median nerve
c) Ulnar nerve
d) Axillary nerve
Explanation: Median nerve supplies pronator teres and pronator quadratus. Injury causes loss of pronation. Correct answer: Median nerve. Clinical: pronation deficit helps localize lesion.
Keyword Definitions
• Brachial plexus – Network of nerves formed by anterior rami of C5–T1 supplying upper limb.
• Radial nerve – Largest branch of brachial plexus, supplies extensor compartment of arm and forearm.
• Ulnar nerve – Arises from medial cord, supplies intrinsic hand muscles and medial forearm.
• Median nerve – Formed by medial and lateral cords, supplies anterior forearm and thenar muscles.
• Axillary nerve – Branch of posterior cord, supplies deltoid and teres minor.
• Posterior cord – Formed by posterior divisions of all trunks of brachial plexus.
• Musculocutaneous nerve – Arises from lateral cord, supplies anterior arm muscles.
• Clinical correlation – Radial nerve injury leads to wrist drop and sensory loss in dorsum of hand.
• Surgical relevance – Axillary dissection may endanger nerves such as thoracodorsal and long thoracic.
• Root value – Spinal segmental origin of a peripheral nerve, important in localization of lesions.
• Extensor compartment – Posterior arm and forearm muscles controlled by radial nerve.
Chapter: Anatomy / Upper Limb
Topic: Brachial Plexus
Subtopic: Radial Nerve
Lead Question – 2013
Largest branch of brachial plexus is
a) Ulnar
b) Median
c) Radial
d) Axillary
Explanation: The radial nerve is the largest branch of the brachial plexus. It arises from the posterior cord (C5–T1) and supplies the extensor compartments of the arm and forearm. Correct answer: Radial nerve. Clinically, its injury causes wrist drop and weak hand grip due to loss of extensors.
Guessed Questions for NEET PG
1) Root value of radial nerve is:
a) C5–C6
b) C5–T1
c) C7–T1
d) C6–C8
Explanation: Radial nerve is derived from the posterior cord of the brachial plexus with root values C5–T1. Correct answer: C5–T1. Clinically, knowledge of root value helps in diagnosing radiculopathies presenting with upper limb weakness.
2) Nerve injured in mid-shaft fracture of humerus:
a) Median
b) Ulnar
c) Radial
d) Axillary
Explanation: Radial nerve runs in the spiral groove of the humerus and is commonly injured in mid-shaft fractures. Correct answer: Radial nerve. This results in wrist drop due to paralysis of wrist extensors.
3) Which nerve supplies triceps brachii?
a) Axillary
b) Radial
c) Median
d) Musculocutaneous
Explanation: Triceps brachii, the main extensor of the elbow, is innervated by the radial nerve. Correct answer: Radial nerve. Clinical: injury above triceps branches causes loss of elbow extension along with wrist drop.
4) Nerve supply of supinator muscle is:
a) Median
b) Radial (deep branch)
c) Ulnar
d) Musculocutaneous
Explanation: The deep branch of the radial nerve, also called the posterior interosseous nerve, innervates the supinator muscle. Correct answer: Radial (deep branch). Clinical: weakness in supination if injured.
5) Wrist drop is due to injury of:
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Musculocutaneous nerve
Explanation: Wrist drop occurs due to loss of extensor muscles supplied by the radial nerve. Correct answer: Radial nerve. Clinical: seen in humeral shaft fractures or compressive neuropathy ("Saturday night palsy").
6) Which nerve is closely related to spiral groove of humerus?
a) Axillary
b) Median
c) Radial
d) Ulnar
Explanation: The radial nerve courses through the spiral groove of the humerus. Correct answer: Radial nerve. Clinical: susceptible to injury in humeral shaft fractures leading to sensory and motor deficits.
7) Posterior interosseous nerve is a branch of:
a) Median
b) Ulnar
c) Radial
d) Axillary
Explanation: Posterior interosseous nerve is the terminal deep branch of radial nerve after passing through supinator. Correct answer: Radial nerve. Clinical: supplies most extensor muscles of forearm.
8) Which nerve supplies skin over dorsum of first web space?
a) Median
b) Ulnar
c) Radial
d) Musculocutaneous
Explanation: The dorsal digital branch of radial nerve supplies skin of first web space between thumb and index finger. Correct answer: Radial nerve. Clinical: sensory loss here confirms radial nerve lesion.
9) Nerve injured in improper use of crutches (“crutch palsy”):
a) Median
b) Radial
c) Ulnar
d) Axillary
Explanation: Radial nerve injury occurs in axilla due to compression from crutches or prolonged pressure. Correct answer: Radial nerve. Clinical: causes wrist drop and weakness of grip.
10) Which nerve is tested by extension of wrist against resistance?
a) Median
b) Ulnar
c) Radial
d) Axillary
Explanation: Radial nerve integrity is tested by checking wrist extension against resistance. Correct answer: Radial nerve. Clinical: inability indicates lesion of radial nerve or its branches.
Keyword Definitions
• Thoracodorsal nerve – Branch of posterior cord, supplies latissimus dorsi.
• Root value – Spinal nerves contributing fibers to a peripheral nerve.
• Brachial plexus – Formed by ventral rami of C5–T1, supplies upper limb.
• Latissimus dorsi – Muscle aiding extension, adduction, and medial rotation of humerus.
• Posterior cord – Division of brachial plexus formed by posterior divisions of all trunks.
• Axillary nerve – Terminal branch of posterior cord, innervates deltoid and teres minor.
• Long thoracic nerve – Arises from C5–C7 roots, supplies serratus anterior.
• Suprascapular nerve – Arises from upper trunk, supplies supraspinatus and infraspinatus.
• Clinical correlation – Injury to thoracodorsal nerve impairs arm adduction, weakens shoulder extension.
• Surgical relevance – Preserved during axillary clearance to maintain latissimus dorsi flap viability.
Chapter: Anatomy / Upper Limb
Topic: Brachial Plexus
Subtopic: Thoracodorsal Nerve
Lead Question – 2013
Root value of thoracodorsal nerve?
a) C5, C6, C7
b) C8, T1
c) C6, C7, C8
d) T1, T2
Explanation: Thoracodorsal nerve arises from the posterior cord of brachial plexus with root value C6, C7, and C8. It innervates latissimus dorsi, which is important in climbing and swimming. Correct answer: C6, C7, C8. Clinically preserved during axillary dissections to prevent functional loss of shoulder movements.
Guessed Questions for NEET PG
1) Nerve supply of latissimus dorsi is:
a) Thoracodorsal nerve
b) Dorsal scapular nerve
c) Axillary nerve
d) Long thoracic nerve
Explanation: Latissimus dorsi is supplied by the thoracodorsal nerve (C6–C8). Correct answer: Thoracodorsal nerve. Clinical: important for forceful adduction and extension of the arm, also preserved in reconstructive flap surgeries.
2) Root value of long thoracic nerve is:
a) C5–C7
b) C7–C9
c) C8–T1
d) C5–C6
Explanation: Long thoracic nerve arises from C5, C6, and C7 roots and supplies serratus anterior. Correct answer: C5–C7. Clinical: injury produces winged scapula due to paralysis of serratus anterior.
3) Which nerve is closely related to axillary lymph node dissection?
a) Thoracodorsal nerve
b) Median nerve
c) Ulnar nerve
d) Radial nerve
Explanation: Thoracodorsal nerve lies in the axilla and is at risk during axillary dissection. Correct answer: Thoracodorsal nerve. Clinical: its injury leads to weakness in shoulder extension and loss of latissimus dorsi flap viability.
4) Nerve injured in surgical neck fracture of humerus:
a) Axillary nerve
b) Radial nerve
c) Median nerve
d) Thoracodorsal nerve
Explanation: Axillary nerve winds around the surgical neck of humerus with posterior circumflex humeral artery. Correct answer: Axillary nerve. Clinical: injury causes inability to abduct shoulder beyond 15° and loss of sensation over deltoid patch.
5) Function of latissimus dorsi is:
a) Flexion and lateral rotation
b) Extension, adduction, medial rotation
c) Abduction and supination
d) Flexion and pronation
Explanation: Latissimus dorsi is a powerful extensor, adductor, and medial rotator of the arm. Correct answer: Extension, adduction, medial rotation. Clinical: active in climbing and swimming movements.
6) Root value of axillary nerve:
a) C5–C6
b) C7–C8
c) C8–T1
d) C5–C7
Explanation: Axillary nerve arises from posterior cord with root value C5 and C6. Correct answer: C5–C6. Clinical: injured in humeral fractures causing deltoid paralysis and sensory loss on upper arm.
7) Which nerve supplies serratus anterior?
a) Long thoracic nerve
b) Thoracodorsal nerve
c) Dorsal scapular nerve
d) Axillary nerve
Explanation: Serratus anterior is innervated by the long thoracic nerve (C5–C7). Correct answer: Long thoracic nerve. Clinical: injury produces winged scapula, especially during axillary lymph node dissection.
8) Root value of suprascapular nerve:
a) C5–C6
b) C6–C7
c) C8–T1
d) C5–C7
Explanation: Suprascapular nerve arises from the upper trunk of brachial plexus with root value C5–C6. Correct answer: C5–C6. Clinical: supplies supraspinatus and infraspinatus, important in shoulder abduction and external rotation.
9) Which nerve injury causes wrist drop?
a) Ulnar nerve
b) Median nerve
c) Radial nerve
d) Thoracodorsal nerve
Explanation: Radial nerve injury leads to paralysis of wrist extensors causing wrist drop. Correct answer: Radial nerve. Clinical: commonly seen in mid-shaft humerus fractures.
10) Klumpke’s palsy involves injury to:
a) Upper trunk (C5–C6)
b) Lower trunk (C8–T1)
c) Posterior cord
d) Medial cord
Explanation: Klumpke’s palsy occurs due to lower trunk (C8–T1) injury. Correct answer: Lower trunk (C8–T1). Clinical: causes claw hand deformity and weakness of intrinsic hand muscles.
Keyword Definitions
• Brachial plexus – A network of nerves formed by ventral rami of C5–T1, supplying upper limb.
• Infraclavicular branches – Nerves arising below clavicle from cords of brachial plexus.
• Supraclavicular branches – Nerves arising above clavicle, mainly from roots and trunks.
• Ulnar nerve – Terminal branch of medial cord; motor to intrinsic hand muscles and sensory to medial hand.
• Long thoracic nerve – Supraclavicular branch from roots (C5–C7); supplies serratus anterior.
• Axillary nerve – Terminal branch of posterior cord; supplies deltoid and teres minor.
• Thoracodorsal nerve – Branch of posterior cord; supplies latissimus dorsi.
• Cords of brachial plexus – Named medial, lateral, posterior according to relation with axillary artery.
• Clinical correlation – Injury to long thoracic nerve causes winging of scapula.
• Fascial compartments – Axilla contains cords of plexus, vessels, and lymph nodes surrounded by sheath.
Chapter: Anatomy / Upper Limb
Topic: Brachial Plexus
Subtopic: Infraclavicular vs Supraclavicular Branches
Lead Question – 2013
All are infraclavicular branches of brachial plexus except?
a) Ulnar nerve
b) Long thoracic nerve
c) Axillary nerve
d) Thoracodorsal nerve
Explanation: Infraclavicular branches arise from cords of brachial plexus. Ulnar, axillary, and thoracodorsal nerves are infraclavicular. Long thoracic nerve arises from roots above the clavicle, hence it is supraclavicular. Correct answer: Long thoracic nerve. Clinically, injury to this nerve produces winged scapula due to serratus anterior paralysis.
Guessed Questions for NEET PG
1) Which nerve is injured in winged scapula?
a) Axillary nerve
b) Long thoracic nerve
c) Thoracodorsal nerve
d) Dorsal scapular nerve
Explanation: Winged scapula occurs due to paralysis of serratus anterior muscle from long thoracic nerve injury. Correct answer: Long thoracic nerve. Clinical: commonly injured in axillary dissections or trauma to lateral thoracic wall.
2) Axillary nerve supplies which muscle?
a) Latissimus dorsi
b) Teres major
c) Teres minor
d) Pectoralis minor
Explanation: Axillary nerve innervates deltoid and teres minor. Correct answer: Teres minor. Clinical: Injury causes inability to abduct shoulder beyond 15° and loss of sensation over deltoid patch.
3) Thoracodorsal nerve supplies:
a) Pectoralis major
b) Latissimus dorsi
c) Subscapularis
d) Serratus anterior
Explanation: Thoracodorsal nerve (middle subscapular nerve) arises from posterior cord and supplies latissimus dorsi. Correct answer: Latissimus dorsi. Clinical: important in flap surgeries like latissimus dorsi flap for reconstruction.
4) Ulnar nerve lesion at wrist causes:
a) Wrist drop
b) Claw hand
c) Ape thumb
d) Foot drop
Explanation: Ulnar nerve injury at wrist leads to claw hand due to loss of intrinsic hand muscles. Correct answer: Claw hand. Clinical: common in fractures of hook of hamate or lacerations.
5) Which is a supraclavicular branch of brachial plexus?
a) Musculocutaneous nerve
b) Long thoracic nerve
c) Median nerve
d) Ulnar nerve
Explanation: Long thoracic nerve arises from roots (C5–C7) above the clavicle, making it a supraclavicular branch. Correct answer: Long thoracic nerve. Clinical: vulnerable during axillary lymph node dissection.
6) Which cord gives rise to median nerve?
a) Lateral cord only
b) Medial cord only
c) Both medial and lateral cords
d) Posterior cord
Explanation: Median nerve arises from contributions of both medial and lateral cords. Correct answer: Both medial and lateral cords. Clinical: median nerve lesions cause loss of thumb opposition and ape thumb deformity.
7) Posterior cord of brachial plexus gives rise to:
a) Axillary and radial nerves
b) Ulnar and radial nerves
c) Median and ulnar nerves
d) Musculocutaneous and median nerves
Explanation: Posterior cord terminates as axillary and radial nerves. Correct answer: Axillary and radial nerves. Clinical: injuries affect shoulder abduction and wrist extension respectively.
8) Klumpke’s palsy involves which roots?
a) C5–C6
b) C7
c) C8–T1
d) C5–C7
Explanation: Klumpke’s palsy occurs due to injury to C8–T1 roots, affecting intrinsic hand muscles. Correct answer: C8–T1. Clinical: causes claw hand deformity and sensory loss in medial forearm and hand.
9) Erb’s palsy involves paralysis of:
a) Flexors of forearm
b) Extensors of wrist
c) Abductors and lateral rotators of shoulder
d) Intrinsic muscles of hand
Explanation: Erb’s palsy occurs due to C5–C6 root lesion, affecting deltoid, supraspinatus, infraspinatus, and biceps. Correct answer: Abductors and lateral rotators of shoulder. Clinical: arm hangs medially rotated, extended, pronated (“waiter’s tip”).
10) Which nerve accompanies posterior circumflex humeral artery?
a) Musculocutaneous nerve
b) Radial nerve
c) Axillary nerve
d) Median nerve
Explanation: Axillary nerve travels with posterior circumflex humeral artery through quadrangular space. Correct answer: Axillary nerve. Clinical: injured in surgical neck fractures of humerus.
Chapter: Central Nervous System
Topic: Cerebrospinal Fluid
Subtopic: Properties and Clinical Importance of CSF
Keyword Definitions:
CSF: Clear fluid cushioning brain and spinal cord, circulating within ventricles and subarachnoid space.
Arachnoid Villi: Microscopic projections of arachnoid membrane into venous sinuses, allowing CSF absorption.
Intracranial Pressure: Pressure inside the skull regulated by CSF volume and brain compliance.
CSF pH: Slightly lower (7.33) than plasma (7.40).
Dural Tap: Lumbar puncture procedure for diagnostic/therapeutic collection of CSF.
Lead Question – 2012
Which of the following is NOT TRUE about CSF?
a) Removal of CSF during dural tap causes intense intracranial headache
b) Normally contain no neutrophils
c) Formed by arachnoid villi within the ventricles
d) pH is less than that of plasma
Explanation: The false statement is (c). CSF is formed by the choroid plexus, not arachnoid villi. Arachnoid villi function in absorption into venous circulation. CSF removal during tap causes headache due to traction on meninges. Normal CSF has no neutrophils and a slightly lower pH than plasma. Correct answer: c.
Guessed Question 1
Which structure produces most CSF in adults?
a) Choroid plexus
b) Arachnoid villi
c) Dural sinuses
d) Astrocytes
Explanation: The majority of CSF is secreted by the choroid plexus in lateral, third, and fourth ventricles. Arachnoid villi only absorb it. Production rate is about 500 ml/day. Answer: a.
Guessed Question 2
Which condition is associated with elevated neutrophils in CSF?
a) Viral meningitis
b) Bacterial meningitis
c) Tuberculous meningitis
d) Fungal meningitis
Explanation: Presence of neutrophils in CSF indicates bacterial meningitis. Viral causes lymphocytic predominance, while TB and fungal show mononuclear cells. Thus, neutrophils are highly suggestive of bacterial etiology. Answer: b.
Guessed Question 3
A patient develops severe headache after lumbar puncture. The mechanism is?
a) Rise in CSF pressure
b) Fall in CSF pressure with meningeal traction
c) Dural nerve irritation
d) Arachnoid inflammation
Explanation: Post-lumbar puncture headache results from fall in CSF pressure causing traction on meninges and intracranial structures when upright. It improves on lying down. Answer: b.
Guessed Question 4
Normal CSF pressure in an adult lying on the side is?
a) 30–50 mm H₂O
b) 60–150 mm H₂O
c) 180–250 mm H₂O
d) 300–400 mm H₂O
Explanation: Normal CSF pressure in lateral decubitus position is 60–150 mm H₂O. Above this suggests raised intracranial pressure. Answer: b.
Guessed Question 5
Which of the following is true about CSF circulation?
a) Flows from subarachnoid space to ventricles
b) Produced in arachnoid villi
c) Passes from lateral to third ventricle via foramen of Monro
d) Absorbed in spinal cord
Explanation: CSF flows from lateral ventricles to third ventricle via foramen of Monro. It is produced in choroid plexus and absorbed by arachnoid villi into venous sinuses. Answer: c.
Guessed Question 6
A patient with suspected subarachnoid hemorrhage but normal CT should undergo?
a) EEG
b) Lumbar puncture
c) MRI
d) Skull X-ray
Explanation: In suspected subarachnoid hemorrhage, if CT scan is negative, lumbar puncture to detect xanthochromia in CSF is diagnostic. Answer: b.
Guessed Question 7
CSF glucose is normally?
a) Equal to plasma glucose
b) Two-thirds of plasma glucose
c) Half of plasma glucose
d) Higher than plasma glucose
Explanation: Normal CSF glucose is about two-thirds of plasma glucose. Low glucose levels suggest bacterial, TB, or fungal meningitis. Answer: b.
Guessed Question 8
In tuberculous meningitis, CSF typically shows?
a) High neutrophils, high glucose
b) Lymphocytes, low glucose, high protein
c) Neutrophils, high glucose, low protein
d) Normal findings
Explanation: Tuberculous meningitis is characterized by lymphocytic pleocytosis, low glucose, and high protein. This pattern helps distinguish it from viral or bacterial causes. Answer: b.
Guessed Question 9
Which of the following substances does NOT normally cross the blood-CSF barrier easily?
a) CO₂
b) Oxygen
c) Glucose
d) Plasma proteins
Explanation: The blood-CSF barrier prevents entry of large proteins while allowing gases and glucose. Hence plasma proteins do not cross easily. Answer: d.
Guessed Question 10
Increased opening pressure during lumbar puncture is seen in?
a) Intracranial hypertension
b) Normal pressure hydrocephalus
c) Spinal anesthesia
d) Hypovolemia
Explanation: Raised opening pressure during lumbar puncture is diagnostic of intracranial hypertension. This may result from tumors, hemorrhage, meningitis, or venous sinus thrombosis. Answer: a.
Chapter: Neurology
Topic: Peripheral Nerve Injuries
Subtopic: Types of Nerve Damage
Keyword Definitions:
• Neuropraxia – Temporary conduction block without axonal damage.
• Axonotmesis – Axonal disruption with intact connective tissue sheaths, recovery possible.
• Neurotmesis – Complete nerve transection with poor prognosis.
• Motor march – Sequential return of motor power in regenerating nerves.
• Nerve regeneration – Repair process after injury involving axonal sprouting.
Lead Question - 2012
Motor march is seen in ?
a) Axonotmesis
b) Neurotmesis
c) Neuropraxia
d) Nerve regeneration
Explanation:
Motor march refers to the sequential recovery of muscles supplied by a regenerating nerve, starting from proximal to distal. It is characteristic of nerve regeneration, particularly following axonotmesis. Correct answer: Nerve regeneration.
Guessed Questions for NEET PG
1. In neuropraxia, which of the following is true?
a) Axons are disrupted
b) Myelin sheath conduction block
c) Endoneurium destroyed
d) Recovery not possible
Explanation:
Neuropraxia is the mildest form of nerve injury with myelin sheath block but intact axons. Conduction resumes within weeks. Correct answer: Myelin sheath conduction block.
2. Wallerian degeneration occurs in?
a) Neuropraxia
b) Axonotmesis
c) Myasthenia gravis
d) Multiple sclerosis
Explanation:
When axons are disrupted (axonotmesis or neurotmesis), the distal segment undergoes Wallerian degeneration. It does not occur in neuropraxia. Correct answer: Axonotmesis.
3. Clinical: A patient with complete transection of the radial nerve shows no recovery after months. Likely diagnosis?
a) Neuropraxia
b) Neurotmesis
c) Axonotmesis
d) Neuritis
Explanation:
Neurotmesis is complete nerve transection with disruption of connective tissue sheaths. Spontaneous recovery is poor without surgical repair. Correct answer: Neurotmesis.
4. First sign of nerve regeneration is?
a) Return of sensation
b) Motor march
c) Tinel’s sign
d) Muscle hypertrophy
Explanation:
Tinel’s sign, tingling on percussion over the regenerating nerve, indicates axonal sprouting and is the earliest sign of regeneration. Correct answer: Tinel’s sign.
5. Clinical: A young man with wrist drop after humeral fracture recovers completely in 6 weeks. Likely nerve injury?
a) Neuropraxia
b) Neurotmesis
c) Axonotmesis
d) Axonopathy
Explanation:
Rapid, complete recovery without surgery suggests neuropraxia, a conduction block without axonal disruption. Correct answer: Neuropraxia.
6. Axonotmesis differs from neurotmesis because?
a) Axons preserved
b) Connective tissue sheath preserved
c) No Wallerian degeneration
d) Requires surgical repair
Explanation:
In axonotmesis, axons are destroyed but connective tissue sheaths remain intact, allowing axonal regrowth. Neurotmesis disrupts both. Correct answer: Connective tissue sheath preserved.
7. Rate of peripheral nerve regeneration is approximately?
a) 1 cm/day
b) 1 mm/day
c) 1 mm/week
d) 1 cm/week
Explanation:
Peripheral nerve regeneration typically occurs at a rate of about 1 mm per day, depending on patient age and injury site. Correct answer: 1 mm/day.
8. Clinical: Recovery of biceps before finger flexors after musculocutaneous nerve injury is due to?
a) Proximal-first regeneration
b) Motor march
c) Collateral sprouting
d) Sensory recovery faster
Explanation:
Motor march explains sequential recovery from proximal to distal muscles in nerve regeneration. Correct answer: Motor march.
9. Sunderland classification grade V corresponds to?
a) Neuropraxia
b) Axonotmesis
c) Neurotmesis
d) Demyelination only
Explanation:
Grade V injury in Sunderland classification represents neurotmesis, complete transection of axons and sheaths. Correct answer: Neurotmesis.
10. In nerve regeneration, Schwann cells mainly provide?
a) Structural myelin
b) Pathway for axonal growth
c) Motor endplate repair
d) Sensory transduction
Explanation:
Schwann cells form bands of Büngner, guiding regenerating axons along preserved endoneurial tubes. Correct answer: Pathway for axonal growth.
Keyword Definitions:
Resting Membrane Potential: Electrical potential difference across a cell membrane at rest.
Potassium Equilibrium: Balance between inward and outward K+ movement.
Surface Electrodes: External electrodes that measure global, not intracellular potentials.
Action Potential: Rapid depolarization and repolarization event in excitable tissue.
Sodium-Potassium Pump: Active transport maintaining high intracellular K+ and low Na+.
Lead Question - 2012
Resting membrane potential in nerve fibre
a) Is equal to the potential of ventricular muscle fibre
b) Can be measured by surface electrodes
c) Increases as extracellular K+ increases
d) Depends upon K+ equilibrium
Explanation: Resting membrane potential in nerve fibres is around –70 mV, determined mainly by K+ equilibrium across the membrane. It cannot be measured by surface electrodes, only by microelectrodes. Increased extracellular K+ reduces negativity, not increases it. Correct answer: d) Depends upon K+ equilibrium.
MCQ 2
A patient with hyperkalemia develops reduced resting membrane potential. What mechanism explains this?
a) Increased Na+ conductance
b) Decreased K+ gradient
c) Increased chloride influx
d) Enhanced Na+-K+ ATPase activity
Explanation: Hyperkalemia reduces the concentration gradient for potassium, lowering efflux and reducing negativity of resting potential. Correct answer: b) Decreased K+ gradient.
MCQ 3
Which ion movement contributes most to resting membrane potential?
a) Active calcium transport
b) Sodium influx
c) Potassium efflux
d) Chloride trapping
Explanation: Resting potential is mostly due to passive potassium efflux through leak channels. Na+ and Cl– have smaller roles. Correct answer: c) Potassium efflux.
MCQ 4
What is the approximate value of neuronal resting membrane potential?
a) +30 mV
b) 0 mV
c) –70 mV
d) –120 mV
Explanation: Resting membrane potential in neurons averages –70 mV, reflecting high K+ permeability and Na+/K+ pump activity. Correct answer: c) –70 mV.
MCQ 5
Resting membrane potential is measured using?
a) Surface electrodes
b) Patch clamp or microelectrodes
c) ECG leads
d) EMG surface electrodes
Explanation: Intracellular recording with glass microelectrodes or patch clamp measures true resting potential, not surface electrodes. Correct answer: b) Patch clamp or microelectrodes.
MCQ 6
A patient has hypokalemia. What happens to resting membrane potential?
a) Becomes less negative
b) Becomes more negative
c) No change
d) Oscillates
Explanation: In hypokalemia, extracellular K+ falls, increasing the gradient, making resting potential more negative (hyperpolarized). Correct answer: b) Becomes more negative.
MCQ 7
The Na+/K+ ATPase contributes to resting potential by?
a) Pumping 3 Na+ out and 2 K+ in
b) Pumping 2 Na+ in and 3 K+ out
c) Pumping equal Na+ and K+
d) Passive diffusion of ions
Explanation: The pump actively moves 3 Na+ out for every 2 K+ in, contributing directly to negativity of resting potential. Correct answer: a) Pumping 3 Na+ out and 2 K+ in.
MCQ 8
In ischemia, resting membrane potential decreases. Why?
a) Excess chloride influx
b) Pump failure due to ATP depletion
c) Enhanced potassium efflux
d) Excessive sodium extrusion
Explanation: ATP depletion in ischemia stops Na+/K+ ATPase, causing Na+ retention, K+ loss, and reduced resting potential. Correct answer: b) Pump failure due to ATP depletion.
MCQ 9
A nerve cell with –70 mV resting potential is depolarized to –50 mV. This means?
a) Membrane becomes more negative
b) Membrane becomes less negative
c) No change in excitability
d) Cell is in refractory period
Explanation: Depolarization reduces negativity, moving closer to threshold and increasing excitability. Correct answer: b) Membrane becomes less negative.
MCQ 10
Which disease involves abnormal resting potential due to ion channel defect?
a) Myasthenia gravis
b) Hyperkalemic periodic paralysis
c) Parkinson’s disease
d) Huntington’s disease
Explanation: In hyperkalemic periodic paralysis, Na+ channel mutations alter resting potential stability, causing episodic weakness. Correct answer: b) Hyperkalemic periodic paralysis.
MCQ 11
Resting membrane potential is closest to equilibrium potential of which ion?
a) Sodium
b) Potassium
c) Chloride
d) Calcium
Explanation: Because of high membrane permeability to K+, resting potential is closest to potassium equilibrium potential. Correct answer: b) Potassium.
Keyword Definitions
• Taste transduction: Mechanisms by which chemical stimuli are converted to neural signals.
• ENaC: Epithelial sodium channels mediating salty taste via Na+ influx.
• Gustducin: Taste G-protein involved in sweet, umami, and bitter signalling cascades.
• PKD2L1: Proton-sensitive channel implicated in sour taste transduction.
• Chorda tympani: Facial nerve branch (VII) carrying anterior two-thirds taste.
• Nucleus tractus solitarius (NTS): Medullary gustatory relay receiving cranial nerve afferents.
• VPM nucleus: Thalamic relay for facial/gustatory sensory information to cortex.
• Dysgeusia: Distorted taste perception commonly seen in disease or after drugs.
• Ageusia: Loss of taste sensation.
• Taste cell turnover: Continuous replacement of taste receptor cells from basal progenitors.
Chapter: Neurophysiology
Topic: Gustation (Taste Physiology)
Subtopic: Taste Transduction Mechanisms and Clinical Correlates
Lead Question – 2012
Salty taste is due to?
a) Ca+2 channels
b) Na+ channels
c) G-protein
d) H+ channels
Explanation: Salt taste transduction primarily occurs via epithelial sodium channels on taste receptor cells which allow Na+ influx, depolarizing the cell and triggering neurotransmitter release to gustatory nerves. This receptor mechanism explains perception of salty stimuli. Answer: b) Na+ channels. Clinically, sodium channel blockers reduce salty perception in experimental settings commonly.
Question 2
Sour taste transduction is primarily mediated by?
a) G-protein coupled receptors
b) Voltage-gated Ca2+ channels
c) ENaC channels
d) H+ (proton) channels
Explanation: Sour taste arises from H+ ions entering taste receptor cells through proton-sensitive channels (e.g., PKD2L1 or HCN modulation), causing depolarization and neurotransmitter release to gustatory afferents. This transduction distinguishes acidity in foods and guides ingestion or rejection. Answer: d) H+ channels. Clinically, sour detection may be reduced in zinc deficiency.
Question 3
Bitter taste receptors transduce signals via which mechanism?
a) ENaC-mediated depolarization
b) Ionotropic glutamate receptors
c) G-protein coupled T2R receptors
d) Direct H+ gating
Explanation: Bitter taste perception relies on G-protein–coupled T2R receptors activating gustducin and PLCβ2, increasing intracellular calcium and neurotransmitter release, signaling potential toxins and causing aversive responses. Genetic variability affects sensitivity to bitter compounds clinically. Answer: c) G-protein. Pharmacologic blockade of these pathways blunts bitter detection during drug therapy in some patients.
Question 4
Sweet taste transduction occurs through?
a) ENaC channels
b) Ionotropic receptors only
c) G-protein coupled T1R receptors
d) H+ channels
Explanation: Sweet taste is mediated by heterodimeric T1R2/T1R3 G-protein–coupled receptors activating gustducin and second messenger cascades, increasing intracellular calcium to depolarize taste cells and signal pleasant carbohydrate-rich nutrition. Artificial sweeteners selectively activate these receptors. Answer: c) G-protein. Clinical disorders like diabetes may alter sweet perception via receptor and central processing changes.
Question 5
Umami (savory) taste primarily uses which receptors?
a) ENaC only
b) Ionotropic serotonin receptors
c) T1R1/T1R3 G-protein receptors or mGluRs
d) Voltage-gated Na+ channels
Explanation: Umami taste responds to L-glutamate via T1R1/T1R3 G-protein–coupled receptors or mGluR receptors, enhancing savory flavor perception and signaling protein-rich foods. Monosodium glutamate exemplifies this transduction. Answer: c) G-protein. Clinical taste disturbances in chemotherapy can reduce umami sensitivity, contributing to anorexia and weight loss requiring dietary counseling often for patient recovery.
Question 6
Taste from anterior two-thirds of tongue is carried by?
a) Chorda tympani (facial nerve VII)
b) Glossopharyngeal nerve (IX)
c) Vagus nerve (X)
d) Hypoglossal nerve (XII)
Explanation: Taste from anterior two-thirds of tongue is transmitted by the chorda tympani branch of facial nerve (VII), carrying modality-specific signals to nucleus of solitary tract. Lesions produce ipsilateral ageusia and dysgeusia impacting appetite and nutrition. Answer: a) Chorda tympani (facial nerve). Testing assesses gustatory function clinically and guides management decisions.
Question 7
First central relay for taste afferents is?
a) Ventral posterolateral nucleus (VPL)
b) Nucleus tractus solitarius (NTS) in medulla
c) Insular cortex directly
d) Hypothalamus
Explanation: Primary central relay for gustatory afferents is the nucleus of the solitary tract in the medulla, receiving inputs from facial, glossopharyngeal, and vagus nerves and projecting to thalamus and cortex for taste perception and reflexes like salivation. Answer: b) Nucleus tractus solitarius (NTS). Lesions impair gustatory reflexes and taste perception.
Question 8
Which pharmacologic agent reduces salty taste by blocking ENaC experimentally?
a) Lidocaine
b) Amiloride
c) Ondansetron
d) Scopolamine
Explanation: Epithelial sodium channel (ENaC) blockers such as amiloride reduce perception of salty taste by inhibiting Na+ entry into taste cells, demonstrating pharmacologic modulation of taste transduction. This informs pathophysiology and potential therapies for dysgeusia. Answer: b) Na+ channels. Clinical trials assess amiloride's effect on taste alteration in various disorders today.
Question 9
Which condition commonly causes ipsilateral anterior two-thirds taste loss?
a) Bell's palsy
b) Stroke of occipital lobe
c) Otitis externa only
d) Myasthenia gravis
Explanation: Bell's palsy commonly causes ipsilateral anterior two-thirds taste loss due to chorda tympani fiber involvement within the facial nerve; patients report dysgeusia and ageusia with associated facial weakness. Distinguishing peripheral facial palsy from central lesions guides prognosis and therapy, often including corticosteroids. Answer: a) Bell's palsy improving recovery in many.
Question 10
Approximate turnover time of taste receptor cells is?
a) Several years
b) Ten to fourteen days
c) Months
d) Hours
Explanation: Taste receptor cells have a high turnover, regenerating from basal progenitors approximately every ten to fourteen days, maintaining gustatory sensitivity and repair after injury; disrupted regeneration from chemotherapy or aging contributes to chronic dysgeusia and nutritional problems. Answer: b) ~10 days. Monitoring taste during chemotherapy aids patient counseling and management.
Question 11
Thalamic relay for taste to cortex is which nucleus?
a) VPL nucleus
b) VPM nucleus
c) Lateral geniculate nucleus
d) Medial geniculate nucleus
Explanation: Gustatory signals ascend to the ventral posteromedial nucleus of the thalamus, which relays taste information to the insular and frontal opercular cortex for conscious perception, discrimination, and hedonic valuation, integrating with olfactory input for flavor. Lesions produce contralateral taste deficits. Answer: b) VPM nucleus. Taste testing aids localization of lesions.
Keyword Definitions
• Vomiting centre: Brainstem nuclei coordinating emesis reflex integrating multisource inputs.
• Area postrema: Chemoreceptor trigger zone at floor of fourth ventricle, outside BBB.
• Nucleus tractus solitarius (NTS): Primary visceral sensory nucleus relaying vagal afferents.
• Chemoreceptor trigger zone (CTZ): Detects blood-borne emetic agents and drugs.
• Vestibular nuclei: Brainstem centers mediating motion and balance inputs causing motion sickness.
• Reticular formation: Medullary network housing central pattern generator for vomiting.
• Ondansetron: 5-HT3 receptor antagonist used for chemotherapy and postoperative nausea.
• Scopolamine: Antimuscarinic antiemetic effective for motion sickness via vestibular blockade.
• Apomorphine: Dopamine agonist that stimulates CTZ and induces vomiting pharmacologically.
• Projectile vomiting: Forceful vomiting often from raised intracranial pressure or posterior fossa lesions.
• NK1 antagonist (Aprepitant): Blocks substance P to prevent chemotherapy-induced nausea and vomiting.
Chapter: Neurophysiology
Topic: Brainstem Reflexes
Subtopic: Vomiting Mechanisms and Clinical Correlates
Lead Question – 2012
Vomiting centre is situated in the: (September 2008)
a) Hypothalamus
b) Midbrain
c) Pons
d) Medulla
Explanation: Vomiting is coordinated by a reflex center located in the medulla oblongata, integrating signals from chemoreceptor trigger zone, vestibular system, GI tract, and higher centers. Lesions or irritants trigger emesis via medullary nuclei. Answer: d) Medulla. This clinically explains why brainstem lesions often produce persistent vomiting and autonomic disturbances.
Question 2
Which structure functions as the chemoreceptor trigger zone for emesis?
a) Nucleus ambiguus
b) Nucleus tractus solitarius
c) Area postrema
d) Dorsal motor nucleus of vagus
Explanation: The chemoreceptor trigger zone lies in the area postrema of the dorsal medulla at the floor of the fourth ventricle, outside the blood-brain barrier, detecting blood-borne emetic agents and drugs. It relays to the vomiting center to initiate emesis. Answer: c) Area postrema. This localization explains sensitivity to chemotherapeutic agents.
Question 3
Visceral afferents from the gastrointestinal tract synapse primarily in which nucleus relevant to vomiting?
a) Hypoglossal nucleus
b) Nucleus tractus solitarius
c) Inferior olivary nucleus
d) Dorsal motor nucleus of vagus
Explanation: Visceral afferents from gastrointestinal tract travel via vagus and glossopharyngeal nerves to the nucleus tractus solitarius in the medulla, which integrates sensory input and projects to the vomiting center and reticular formation. This pathway mediates reflex emesis from gastric irritation or inflammation. Answer: b) Nucleus tractus solitarius clinically important centrally.
Question 4
Which antiemetic class blocks serotonin-mediated vagal and CTZ signals effectively?
a) Dopamine antagonists
b) Anticholinergics
c) 5-HT3 receptor antagonists
d) NK1 receptor antagonists
Explanation: 5-HT3 receptor antagonists such as ondansetron block serotonin-mediated stimulation of vagal afferents and the chemoreceptor trigger zone, effectively preventing chemotherapy-induced and postoperative nausea. They act centrally and peripherally with good efficacy and tolerability and are first-line antiemetics in many protocols. Answer: a) Ondansetron. Widely used clinically for nausea control effectively.
Question 5
Motion sickness and vestibular-induced vomiting primarily involve which structures?
a) Area postrema only
b) Vestibular nuclei
c) Cerebellar vermis only
d) Hypothalamus exclusively
Explanation: Vestibular apparatus and vestibular nuclei in brainstem detect motion and send signals to vomiting center and cerebellum; conflicts between visual and vestibular input provoke motion sickness and emesis via connections to nucleus tractus solitarius and area postrema. Antihistamines reduce vestibular input. Answer: b) Vestibular nuclei. Used antiemetics target this pathway.
Question 6
Which drug class is known to directly stimulate the CTZ and produce emesis historically?
a) Anticholinergics
b) Serotonin antagonists
c) Dopamine agonists (e.g., apomorphine)
d) NK1 antagonists
Explanation: Apomorphine, a dopamine agonist, stimulates D2 receptors in the chemoreceptor trigger zone (area postrema), provoking profound emesis. Historically used as an emetic, it demonstrates pharmacologic activation of vomiting circuits. Dopamine antagonists block this reflex therapeutically. Answer: c) Apomorphine. Now replaced by safer antiemetics in teaching.
Question 7
Strong risk factors for postoperative nausea and vomiting include which of the following?
a) Male sex and smoking
b) Female sex and opioid use
c) Elderly age exclusively
d) Short duration surgeries only
Explanation: Risk factors for postoperative nausea and vomiting include female sex, history of motion sickness or prior PONV, nonsmoking status, use of volatile anesthetics or opioids, lengthy surgery, and younger age. Multimodal prophylaxis reduces incidence by targeting multiple pathways. Answer: b) Female sex and opioid exposure are significant risk contributors clinically.
Question 8
Best prophylactic agent for motion sickness is?
a) Ondansetron
b) Metoclopramide
c) Domperidone
d) Scopolamine
Explanation: Anticholinergic scopolamine applied transdermally blocks muscarinic receptors in vestibular nuclei and central vomiting pathways, preventing motion-induced nausea and vomiting. Histamine H1 antagonists like promethazine also help. Side effects include dry mouth, blurred vision, and sedation. Answer: d) Scopolamine. It is recommended prophylactically for susceptible patients before travel or procedures commonly.
Question 9
The central pattern generator coordinating emesis resides in which region?
a) Medullary reticular formation
b) Hypothalamus
c) Midbrain periaqueductal gray
d) Pontine tegmentum exclusively
Explanation: Emesis results from activation of a central pattern generator located in the medullary reticular formation and adjacent reticular nuclei, coordinating respiratory, upper GI, and pharyngeal muscles to produce vomiting. This network receives multisensory inputs including chemoreceptor trigger zone and vestibular signals. Answer: a) Medullary reticular formation critical for protective reflexes.
Question 10
Projectile vomiting without nausea often indicates which pathology?
a) Gastroenteritis
b) Metabolic alkalosis only
c) Posterior fossa lesion compressing medulla
d) Peripheral vestibular neuritis
Explanation: Projectile vomiting without preceding nausea suggests increased intracranial pressure or posterior fossa lesion compressing medullary centers. Vomiting may be forceful and predominantly nocturnal. Early recognition mandates neuroimaging to identify obstructive hydrocephalus or tumor. Answer: c) Posterior fossa lesion causing medullary compression requiring urgent neurosurgical decompression to prevent herniation and death.
Question 11
Which agent is recommended to prevent both acute and delayed chemotherapy-induced emesis when combined with others?
a) Ondansetron alone
b) Aprepitant (NK1 antagonist)
c) Metoclopramide alone
d) Scopolamine patch
Explanation: Aprepitant, an NK1 receptor antagonist, blocks substance P signaling in vomiting pathways, reducing acute and delayed chemotherapy-induced nausea and vomiting when combined with 5-HT3 antagonists and corticosteroids. It improves control of emesis after highly emetogenic chemotherapy. Answer: b) Aprepitant. Recommended in guidelines for high emetic risk regimens to reduce vomiting.
Keyword Definitions
• Spinocerebellar tract: Pathways conveying unconscious proprioception to cerebellum for coordination.
• Dorsal spinocerebellar: Ipsilateral lower limb proprioceptive tract entering via inferior peduncle.
• Ventral spinocerebellar: Tract that double-crosses and conveys integrated movement signals to cerebellum.
• Cuneocerebellar: Upper limb equivalent of dorsal spinocerebellar, via accessory cuneate nucleus.
• Clarke’s column: Nucleus dorsalis (T1–L2) origin of dorsal spinocerebellar fibres.
• Inferior cerebellar peduncle: Major cerebellar input for dorsal spinocerebellar and cuneocerebellar tracts.
• Unconscious proprioception: Automatic sensory feedback used to adjust movement without awareness.
• Dysmetria: Overshoot or undershoot of target during voluntary movement, sign of cerebellar dysfunction.
• Intention tremor: Tremor appearing during voluntary movement, characteristic of cerebellar disease.
• Romberg sign: Sway or fall on eye closure from proprioceptive loss (dorsal column), not cerebellar typically.
• Heel-to-shin: Bedside test for lower limb cerebellar coordination and spinocerebellar function.
Chapter: Neurophysiology
Topic: Cerebellar Systems
Subtopic: Spinocerebellar Tracts and Function
Lead Question – 2012
True about spinocerebellar tract is?
a) Equilibrium
b) Smoothens and coordinates movement
c) Learning induced by change in vestibulo ocular reflex
d) Planning and programming
Explanation: Spinocerebellar tracts carry unconscious proprioceptive information from muscles and joints to the cerebellum, enabling real-time adjustment of ongoing movements and posture. They assist coordination and timing rather than motor planning or voluntary initiation. Therefore they smooth and coordinate movement. Answer: b) Smoothens and coordinates movement for precise limb control continuously.
Question 2
Dorsal spinocerebellar tract originates from which nucleus?
a) Clarke’s column
b) Accessory cuneate nucleus
c) Inferior olivary nucleus
d) Red nucleus
Explanation: The dorsal spinocerebellar tract arises from Clarke’s column (nucleus dorsalis) in spinal segments T1 to L2, conveying ipsilateral proprioceptive information from lower limbs to the cerebellum via the inferior cerebellar peduncle. It does not decussate. Answer: a) Clarke’s column. This tract is essential for unconscious proprioception and limb coordination clinically.
Question 3
A lesion of spinocerebellar tract produces which clinical sign?
a) Ipsilateral limb ataxia
b) Contralateral weakness
c) Loss of vibration sense only
d) Sensory level with aneasthesia
Explanation: Spinocerebellar tract lesions produce ipsilateral limb ataxia because most cerebellar afferents enter the cerebellum without crossing or double-cross, preserving same-side representation. Patients show dysmetria, decomposition of movement, and intention tremor on the affected side. Answer: a) Ipsilateral limb ataxia. Coordination deficits worsen with eyes closed and during rapid alternating movements.
Question 4
Which is true about ventral spinocerebellar tract?
a) It never crosses
b) It conveys conscious proprioception
c) It double-crosses
d) It terminates in thalamus
Explanation: The ventral spinocerebellar tract transmits integrated proprioceptive and interneuronal activity related to ongoing limb movement. It decussates twice: once in the spinal cord and again within the cerebellum, resulting in ipsilateral cerebellar representation ultimately. Answer: c) It double-crosses to reach the cerebellum. This anatomical feature explains localization of cerebellar signs.
Question 5
Primary modality carried by spinocerebellar tracts is?
a) Conscious proprioception
b) Unconscious proprioception
c) Pain and temperature
d) Fine tactile discrimination
Explanation: Spinocerebellar pathways convey unconscious proprioception from muscle spindles and Golgi tendon organs to cerebellar cortex, enabling automatic postural adjustments and gait coordination. They are distinct from dorsal columns that mediate conscious proprioception. Answer: b) Unconscious proprioception. Clinical lesions produce ataxia yet preserve conscious position sense; coordination testing reveals deficits often.
Question 6
Finger-to-nose test primarily assesses which system?
a) Cerebellar coordination including spinocerebellar input
b) Dorsal column conscious proprioception only
c) Spinothalamic tract function
d) Pyramidal tract strength
Explanation: Finger-to-nose test evaluates cerebellar coordination and proprioceptive integration including spinocerebellar inputs. Dysmetria, intention tremor, and decomposition of movement during this test indicate cerebellar dysfunction. It does not differentiate conscious from unconscious proprioception but assesses functional output of cerebellum. Answer: a) True. Clinically helps localize lesion to hemisphere or vermis region.
Question 7
Which hereditary disease affects spinocerebellar tracts prominently?
a) Multiple sclerosis
b) Amyotrophic lateral sclerosis
c) Friedreich ataxia
d) Myasthenia gravis
Explanation: Friedreich ataxia causes degeneration of spinocerebellar tracts, dorsal columns, and corticospinal tracts due to frataxin deficiency. Patients present with progressive gait ataxia, loss of vibration and proprioception, areflexia, and cardiomyopathy. Genetic testing confirms GAA repeat expansion. Answer: c) Friedreich ataxia. Onset usually adolescence; progression causes severe disability needing supportive care.
Question 8
Dorsal spinocerebellar fibres enter cerebellum via which peduncle?
a) Inferior cerebellar peduncle
b) Middle cerebellar peduncle
c) Superior cerebellar peduncle
d) None of the above
Explanation: Dorsal spinocerebellar fibers ascend ipsilaterally and enter cerebellum through the inferior cerebellar peduncle, carrying lower limb proprioceptive information. Ventral spinocerebellar fibers primarily enter via superior peduncle after double crossing. Knowledge of peduncle entry assists lesion localization. Answer: a) Inferior cerebellar peduncle. Distinguishing peduncle entry aids accurate lesion localization clinically rapidly.
Question 9
Romberg sign in spinocerebellar or cerebellar lesions is usually?
a) Positive only with eyes open
b) Negative (does not depend on vision)
c) Positive only with vibration loss
d) Always bilateral sensory level
Explanation: Romberg sign becomes positive when proprioceptive input via dorsal columns is lost, causing increased sway with eye closure. Cerebellar or spinocerebellar lesions produce ataxia independent of visual input, so patients remain unstable with eyes open and closed; Romberg is typically negative. Answer: b) Negative. Clinical testing distinguishes lesion location effectively.
Question 10
Best bedside test for lower limb spinocerebellar function is?
a) Romberg test alone
b) Vibration at toe only
c) Rapid alternating foot movements only
d) Heel-to-shin test
Explanation: Heel-to-shin maneuver tests lower limb coordination and cerebellar integration of proprioceptive input including spinocerebellar feedback. Patients with spinocerebellar tract or cerebellar hemisphere lesions exhibit dysmetria and inability to maintain a smooth, straight movement along the shin. Answer: d) Heel-to-shin test. It detects ipsilateral coordination deficits and helps lateralize lesions accurately.
Question 11
Unconscious proprioception from the upper limb is conveyed by?
a) Dorsal spinocerebellar tract
b) Cuneocerebellar tract
c) Ventral spinothalamic tract
d) Lateral corticospinal tract
Explanation: Cuneocerebellar tract carries unconscious proprioceptive input from upper limbs via accessory cuneate nucleus to the cerebellum through inferior peduncle, analogous to dorsal spinocerebellar tract for lower limbs. Lesions impair ipsilateral upper limb coordination and contribute to ataxia. Answer: b) Cuneocerebellar tract. Clinically causes dysmetria and intention tremor during voluntary tasks.
Keyword Definitions
• Proprioception: Sense of position and movement from muscles and joints.
• Vibration sense: Perception of oscillatory stimuli via large myelinated fibers.
• Dorsal columns: Ascending pathway for fine touch, vibration, and proprioception.
• Medial lemniscus: Brainstem tract formed by decussated dorsal column fibers.
• Fasciculus gracilis: Dorsal column for lower limb and trunk below T6.
• Fasciculus cuneatus: Dorsal column for upper limb and trunk above T6.
• VPL nucleus: Thalamic relay for body somatosensation to cortex.
• Romberg sign: Instability on eye closure indicating proprioceptive loss.
• Brown-Séquard syndrome: Hemisection causing ipsilateral dorsal column loss, contralateral pain loss.
• Tabes dorsalis: Neurosyphilis causing posterior column degeneration and sensory ataxia.
• Syringomyelia: Central canal cavity causing bilateral pain/temperature loss with spared dorsal columns.
• Asterognosis: Inability to recognize objects by touch despite intact basic sensation.
• Large-fiber neuropathy: Peripheral nerve disorder affecting vibration and position sense early.
Chapter: Neurophysiology
Topic: Somatosensory Pathways
Subtopic: Dorsal Column–Medial Lemniscus System
Lead Question – 2012
Loss of proprioception & fine touch ?
a) Anterior spinothalamic tract
b) Lateral spinothalamic tract
c) Dorsal column
d) Corticospinal tract
Explanation: Loss of proprioception, vibration, and fine discriminative touch indicates dorsal column–medial lemniscus pathway dysfunction. Large myelinated fibers ascend ipsilaterally to gracile and cuneate nuclei, then decussate to medial lemniscus and VPL. Answer: c) Dorsal column. Spinothalamic tracts carry pain and temperature; corticospinal mediates voluntary movement, not somatosensory modalities, primarily pathways.
Question 2
A 55-year-old with numb feet, gait unsteadiness, and positive Romberg has impaired vibration at toes. Which pathway is damaged?
a) Dorsal columns
b) Lateral corticospinal tract
c) Spinothalamic tract
d) Vestibulospinal tract
Explanation: Subacute combined degeneration from vitamin B12 deficiency damages large myelinated posterior column fibers, producing sensory ataxia, impaired vibration, and proprioceptive loss in legs. Answer: a) Dorsal columns. Lateral corticospinal damage causes weakness and spasticity; spinothalamic lesions impair pain and temperature; vestibulospinal tracts mediate balance reflexes without conveying discriminative touch signals.
Question 3
After a knife injury causing right T10 hemisection, which deficit occurs on the right below the lesion?
a) Loss of pain and temperature
b) Loss of vibration and proprioception
c) Flaccid paralysis below lesion
d) Bilateral pain loss
Explanation: Brown-Séquard hemisection causes ipsilateral loss of dorsal column modalities below the lesion from uncrossed ascent, and contralateral pain/temperature loss after spinothalamic decussation. Answer: b) Loss of vibration and proprioception. Flaccid paralysis occurs at the level from anterior horn involvement, not below. Bilateral pain loss suggests central cord lesions, not hemisection.
Question 4
Which thalamic nucleus relays body fine touch, vibration, and proprioception to cortex?
a) VPL nucleus
b) VPM nucleus
c) Lateral geniculate nucleus
d) Medial geniculate nucleus
Explanation: The ventral posterolateral thalamic nucleus relays somatosensory information from body—both medial lemniscus and spinothalamic—to the primary somatosensory cortex. Lesions impair discriminative touch, vibration, and proprioception contralaterally. Answer: a) VPL nucleus. VPM handles facial sensation; LGN vision; MGN audition. Precise localization of body sensation depends critically on intact VPL relay neurons.
Question 5
A patient with lightning pains, wide-based gait, and positive Romberg likely has damage to which structure?
a) Dorsal columns
b) Spinocerebellar tracts
c) Ventral horn cells
d) Substantia nigra
Explanation: Tabes dorsalis from neurosyphilis degenerates dorsal columns and roots, causing lightning pains, sensory ataxia, impaired vibration, and positive Romberg sign. Answer: a) Dorsal columns. Spinocerebellar tract disease produces limb ataxia without Romberg positivity; ventral horn disease causes lower motor neuron weakness; substantia nigra degeneration produces Parkinsonism, not sensory ataxia, classically.
Question 6
Fine touch from the right hand ascends initially in which tract?
a) Spinothalamic tract
b) Fasciculus gracilis
c) Fasciculus cuneatus
d) Dorsal spinocerebellar tract
Explanation: Fine touch and proprioceptive signals from the upper limb ascend in the ipsilateral fasciculus cuneatus to synapse in the cuneate nucleus before crossing as internal arcuate fibers. Answer: c) Fasciculus cuneatus. Fasciculus gracilis conveys lower limb input; spinothalamic carries pain and temperature; dorsal spinocerebellar conveys unconscious proprioception, not discriminative touch.
Question 7
A patient cannot identify a key by touch in the left hand, yet basic touch is intact. Likely lesion?
a) Cerebellar hemisphere
b) Postcentral gyrus
c) Precentral gyrus
d) Dorsal horn
Explanation: Inability to recognize objects by touch with intact primary modalities indicates cortical sensory loss—astereognosis—from a contralateral parietal lesion, usually postcentral gyrus (primary somatosensory cortex). Answer: b) Postcentral gyrus. Precentral gyrus is motor; cerebellum coordinates movement but not stereognosis; dorsal columns carry signals, yet cortical interpretation is required for object recognition.
Question 8
Bilateral loss of pain and temperature over shoulders with preserved vibration suggests which tract is spared?
a) Spinothalamic tract
b) Lateral corticospinal tract
c) Anterior horn cells
d) Dorsal columns
Explanation: Syringomyelia damages decussating anterior commissural spinothalamic fibers in the cervical cord, causing bilateral cape-like pain and temperature loss while sparing dorsal column modalities. Answer: d) Dorsal columns are spared. Thus vibration and proprioception remain intact. Lateral corticospinal may be affected later causing weakness; dorsal spinocerebellar mediates unconscious proprioception effectively overall.
Question 9
A medial medullary infarct damaging the medial lemniscus causes which deficit?
a) Ipsilateral pain and temperature loss
b) Loss of contralateral discriminative touch
c) Ipsilateral loss of vibration
d) Bilateral pain loss
Explanation: A medial medullary lesion involving the medial lemniscus produces contralateral loss of fine touch, vibration, and proprioception from body due to disruption of dorsal column fibers. Answer: b) Loss of contralateral discriminative touch. Pain and temperature are carried by spinothalamic tract located laterally; hypoglossal involvement would cause ipsilateral tongue weakness.
Question 10
Which modality is typically earliest impaired in large-fiber diabetic neuropathy?
a) Impaired vibration sense
b) Spasticity
c) Hyperalgesia
d) Nystagmus
Explanation: Large-fiber peripheral neuropathy in diabetes affects vibration and position sense earliest, causing positive Romberg and sensory ataxia. Answer: a) Impaired vibration sense. Pain and temperature rely on small fibers; strength may be preserved; hyperreflexia suggests upper motor neuron disease, not peripheral neuropathy, which typically shows reduced or absent ankle reflexes.
Question 11
Which bedside test best assesses dorsal column proprioception?
a) Graphesthesia on palm
b) Vibration at medial malleolus
c) Great toe position sense
d) Hot/cold discrimination
Explanation: Testing joint position at the great toe assesses conscious proprioception via dorsal columns and medial lemniscus. Eyes are closed to remove visual cues. Answer: c) Great toe position sense. Tuning fork tests vibration, not position; pinprick examines spinothalamic pain; plantar response assesses corticospinal integrity, unrelated to dorsal column proprioceptive function.
Keyword Definitions
• Dopamine: Catecholamine neurotransmitter crucial for motor control, motivation, and reward pathways.
• Nigrostriatal pathway: Dopaminergic pathway projecting from substantia nigra to striatum, vital for movement regulation.
• Serotonin: Neurotransmitter involved in mood, sleep, and appetite regulation.
• Cholinergic neurons: Use acetylcholine, important in learning, memory, and motor circuits.
• Adrenergic neurons: Release norepinephrine, essential for arousal, vigilance, and autonomic functions.
• Substantia nigra: Midbrain nucleus producing dopamine, degeneration causes Parkinsonism.
• Basal ganglia: Group of nuclei modulating movement initiation and suppression.
• Extrapyramidal system: Motor system controlling posture, tone, and coordination.
• Parkinson’s disease: Neurodegenerative disorder due to dopaminergic loss in nigrostriatal pathway.
• Dyskinesia: Involuntary abnormal movements due to neurotransmitter imbalance.
• Levodopa: Dopamine precursor used as therapy in Parkinson’s disease.
Chapter: Neurophysiology
Topic: Basal Ganglia
Subtopic: Nigrostriatal Pathway
Lead Question – 2012
Neurotransmitter involved in nigrostriatal pathway is?
a) Serotonin
b) Dopamine
c) Cholinergic
d) Adrenergic
Explanation: The nigrostriatal pathway is a dopaminergic tract connecting substantia nigra pars compacta with the striatum. It regulates voluntary movement by balancing excitatory and inhibitory signals in basal ganglia circuits. Loss of dopamine here causes Parkinsonism. Answer: b) Dopamine. Other neurotransmitters modulate but dopamine is the principal one involved.
Question 2
Which brain structure degenerates in Parkinson’s disease?
a) Substantia nigra pars compacta
b) Globus pallidus externa
c) Red nucleus
d) Subthalamic nucleus
Explanation: Parkinson’s disease arises from dopaminergic neuronal loss in substantia nigra pars compacta, leading to striatal dopamine deficiency. This impairs basal ganglia modulation, causing bradykinesia, rigidity, and tremor. Answer: a) Substantia nigra pars compacta. Subthalamic nucleus lesions cause hemiballismus, while pallidal and red nucleus lesions show different deficits.
Question 3
Which dopamine receptor subtype facilitates the direct pathway in basal ganglia?
a) D1 receptors
b) D2 receptors
c) D3 receptors
d) D4 receptors
Explanation: D1 receptors in striatum stimulate the direct pathway, enhancing movement by exciting striatal neurons projecting to internal globus pallidus. Dopamine binding here increases activity, disinhibiting thalamus and promoting cortical excitation. Answer: a) D1 receptors. D2 receptors inhibit indirect pathway, while D3 and D4 are extrastriatal predominantly.
Question 4
Which clinical feature is not typical of Parkinson’s disease?
a) Rest tremor
b) Bradykinesia
c) Rigidity
d) Spastic paralysis
Explanation: Parkinson’s disease is characterized by rest tremor, bradykinesia, rigidity, and postural instability. Spastic paralysis occurs in upper motor neuron lesions, not basal ganglia dysfunction. Answer: d) Spastic paralysis. Distinguishing Parkinsonism from pyramidal tract damage clinically relies on absence of spasticity and hyperreflexia, despite motor difficulties and tremors.
Question 5
Which neurotransmitter imbalance causes Huntington’s disease?
a) Loss of GABA and acetylcholine
b) Excess dopamine
c) Loss of dopamine
d) Increased serotonin
Explanation: Huntington’s disease features degeneration of striatal GABAergic and cholinergic neurons, combined with relative dopaminergic overactivity. This imbalance produces choreiform hyperkinetic movements. Answer: a) Loss of GABA and acetylcholine. Dopamine blockade may reduce symptoms, unlike Parkinson’s disease where dopamine replacement is therapeutic and symptomatically beneficial clinically.
Question 6
Which drug increases brain dopamine by crossing blood-brain barrier?
a) Levodopa
b) Dopamine
c) Carbidopa
d) Bromocriptine
Explanation: Dopamine itself cannot cross the blood-brain barrier. Levodopa, its precursor, is converted to dopamine in brain. Carbidopa prevents peripheral breakdown, enhancing central availability. Answer: a) Levodopa. Bromocriptine is a dopamine agonist, while dopamine injection only acts peripherally without improving Parkinson’s motor symptoms effectively within CNS.
Question 7
Which basal ganglia lesion produces hemiballismus?
a) Subthalamic nucleus
b) Putamen
c) Caudate nucleus
d) Globus pallidus interna
Explanation: Hemiballismus, a flinging hyperkinetic movement disorder, occurs due to contralateral subthalamic nucleus lesion. Subthalamus normally excites globus pallidus interna, inhibiting thalamus. Its damage reduces inhibition, causing excessive cortical motor output. Answer: a) Subthalamic nucleus. Other basal ganglia nuclei lesions cause Parkinsonism or chorea, not violent ballistic movements.
Question 8
Which dopaminergic pathway is associated with reward and addiction?
a) Nigrostriatal pathway
b) Mesolimbic pathway
c) Tuberoinfundibular pathway
d) Mesocortical pathway
Explanation: Mesolimbic pathway projects from ventral tegmental area to nucleus accumbens, mediating reward, reinforcement, and addiction. Answer: b) Mesolimbic pathway. Nigrostriatal controls movement, mesocortical regulates cognition and emotion, and tuberoinfundibular inhibits prolactin secretion. Dopamine thus has multiple distinct functional pathways in the central nervous system overall.
Question 9
Blockade of which dopamine pathway leads to drug-induced Parkinsonism?
a) Mesolimbic
b) Mesocortical
c) Nigrostriatal
d) Tuberoinfundibular
Explanation: Antipsychotic drugs blocking D2 receptors in the nigrostriatal pathway cause extrapyramidal symptoms resembling Parkinson’s disease. Answer: c) Nigrostriatal. Mesolimbic blockade improves psychosis, mesocortical blockade causes cognitive dulling, and tuberoinfundibular blockade elevates prolactin. Understanding pathway selectivity helps minimize antipsychotic side effects clinically during patient treatment overall effectively.
Question 10
Stimulation of which dopamine receptor subtype inhibits indirect pathway activity?
a) D1
b) D2
c) D3
d) D5
Explanation: D2 receptors inhibit striatal neurons of the indirect pathway, reducing thalamic suppression and promoting movement. Answer: b) D2. D1 receptors activate direct pathway, D3 and D5 have roles in limbic and cortical areas. Balanced D1/D2 signaling ensures smooth motor control within basal ganglia circuits clinically.
Question 11
Which hypothalamic hormone secretion is inhibited by tuberoinfundibular dopamine pathway?
a) Growth hormone
b) Cortisol
c) Prolactin
d) Thyroxine
Explanation: Dopaminergic neurons of tuberoinfundibular pathway inhibit prolactin release from anterior pituitary lactotrophs. Blockade or damage increases prolactin, causing galactorrhea and infertility. Answer: c) Prolactin. Dopamine agonists treat hyperprolactinemia, while antagonists may induce it. Other hypothalamic hormones are regulated differently by respective hypothalamic releasing factors clinically overall.
Keyword Definitions
• Purkinje fibres: Large inhibitory neurons of cerebellar cortex using GABA as neurotransmitter.
• Deep cerebellar nuclei: Primary output centres of cerebellum receiving inhibitory Purkinje input.
• Climbing fibres: Excitatory inputs from inferior olivary nucleus synapsing on Purkinje cells.
• Mossy fibres: Excitatory afferents from spinal cord and brainstem projecting to granule cells.
• Basket cells: Inhibitory interneurons forming axo-somatic synapses on Purkinje cells.
• Stellate cells: Inhibitory interneurons acting on Purkinje dendrites in molecular layer.
• Spinocerebellar tracts: Convey unconscious proprioceptive information from muscles and joints.
• Granule cells: Excitatory interneurons giving rise to parallel fibres synapsing on Purkinje cells.
• GABA: Gamma-aminobutyric acid, main inhibitory neurotransmitter in CNS.
• Cerebellar cortex: Three-layered structure modulating motor coordination and balance.
• Motor learning: Cerebellar mechanism for adapting and fine-tuning skilled movements.
Chapter: Neurophysiology
Topic: Cerebellum
Subtopic: Purkinje Cell Function
Lead Question – 2012
Purkinje fibres are inhibitory for?
a) Deep cerebellar nuclei
b) Climbing fibre
c) Basket cells
d) Spinocerebellar tracts
Explanation: Purkinje cells are GABAergic neurons that project inhibitory signals to deep cerebellar nuclei, regulating motor output precision. They receive excitatory input from climbing and mossy fibres, while interneurons like basket and stellate cells refine their activity. Answer: a) Deep cerebellar nuclei. This inhibitory control ensures smooth coordination and balance.
Question 2
Which neurotransmitter is released by Purkinje cells?
a) Acetylcholine
b) Dopamine
c) GABA
d) Glutamate
Explanation: Purkinje cells are the sole output of the cerebellar cortex. They are inhibitory neurons releasing gamma-aminobutyric acid (GABA). This neurotransmitter suppresses activity of deep cerebellar nuclei, ensuring controlled modulation of motor output. Answer: c) GABA. Excitatory neurotransmitters like glutamate act via mossy and climbing fibre inputs.
Question 3
A patient has loss of coordination but preserved strength. Which structure is primarily affected?
a) Cerebellum
b) Basal ganglia
c) Motor cortex
d) Spinal cord anterior horn
Explanation: The cerebellum coordinates timing, precision, and smoothness of movement but does not initiate voluntary force generation. Lesions cause ataxia, dysmetria, and intention tremor without significant weakness. Answer: a) Cerebellum. Motor cortex lesions reduce strength, while basal ganglia dysfunction causes rigidity or tremor, not incoordination.
Question 4
Climbing fibres originate from which source?
a) Inferior olivary nucleus
b) Red nucleus
c) Vestibular nuclei
d) Pontine nuclei
Explanation: Climbing fibres arise exclusively from the inferior olivary nucleus and form powerful excitatory synapses directly on Purkinje cells. They regulate motor learning and coordination through long-term depression at parallel fibre synapses. Answer: a) Inferior olivary nucleus. Mossy fibres, instead, arise from pontine and spinal inputs.
Question 5
Damage to Purkinje cells would primarily result in?
a) Spastic paralysis
b) Ataxia
c) Rigidity
d) Hyporeflexia
Explanation: Purkinje cell loss disrupts cerebellar inhibitory control, impairing coordination of movement. This produces ataxia with unsteady gait, dysdiadochokinesia, and intention tremor. Answer: b) Ataxia. Spasticity results from corticospinal damage, rigidity from basal ganglia disease, and hyporeflexia from lower motor neuron lesions.
Question 6
Which interneuron inhibits Purkinje cells in cerebellar cortex?
a) Basket cells
b) Golgi cells
c) Pyramidal cells
d) Oligodendrocytes
Explanation: Basket cells provide inhibitory axo-somatic synapses directly on Purkinje neurons, limiting their firing. Stellate cells also inhibit dendrites. Golgi cells regulate granule cells. Answer: a) Basket cells. These interneurons fine-tune Purkinje output before it reaches deep cerebellar nuclei, optimizing cerebellar motor coordination and timing.
Question 7
Which cerebellar lesion leads to truncal ataxia and swaying while standing?
a) Vermis
b) Hemisphere
c) Flocculonodular lobe
d) Dentate nucleus
Explanation: Lesions in cerebellar vermis cause truncal ataxia with broad-based gait and inability to maintain upright posture. Answer: a) Vermis. Hemisphere lesions cause limb ataxia, flocculonodular lesions cause balance and nystagmus, while dentate involvement produces dysmetria and decomposition of movement. Clinical localization depends on specific cerebellar subdivisions.
Question 8
Mossy fibres synapse first on?
a) Purkinje cells
b) Basket cells
c) Granule cells
d) Stellate cells
Explanation: Mossy fibres relay information from spinal cord and brainstem. They terminate on granule cells in cerebellar cortex, which then give rise to parallel fibres. These parallel fibres excite Purkinje dendrites. Answer: c) Granule cells. Thus, mossy fibres indirectly influence Purkinje output by granule cell activation.
Question 9
Which symptom is most typical of cerebellar disease?
a) Rest tremor
b) Intention tremor
c) Hypokinesia
d) Spasticity
Explanation: Cerebellar lesions produce intention tremor, which appears during voluntary movement and worsens as target is approached. Answer: b) Intention tremor. Rest tremor suggests Parkinsonism, hypokinesia occurs in basal ganglia disease, and spasticity arises from pyramidal tract lesions. Cerebellum chiefly impairs timing and coordination of motor actions.
Question 10
Which cerebellar output nucleus is largest and projects to motor cortex via thalamus?
a) Fastigial nucleus
b) Globose nucleus
c) Dentate nucleus
d) Emboliform nucleus
Explanation: The dentate nucleus is the largest deep cerebellar nucleus, projecting to contralateral motor cortex via the ventrolateral thalamus. It coordinates planning, timing, and fine motor execution. Answer: c) Dentate nucleus. Fastigial controls posture, globose and emboliform modulate intermediate motor activities of limbs.
Question 11
Which tract conveys unconscious proprioception from muscles to cerebellum?
a) Corticospinal tract
b) Spinothalamic tract
c) Spinocerebellar tract
d) Rubrospinal tract
Explanation: Spinocerebellar tracts carry proprioceptive input from muscle spindles and Golgi tendon organs to cerebellum. This unconscious sensory feedback helps adjust movement in real time. Answer: c) Spinocerebellar tract. Corticospinal controls voluntary movement, spinothalamic transmits pain/temperature, rubrospinal influences flexor tone but not proprioception.
Keyword Definitions
• Two-point discrimination: Ability to distinguish two separate simultaneous tactile stimuli.
• Tactile acuity: Sharpness of touch perception depending on receptor density.
• Receptive field: Area of skin innervated by a single sensory neuron.
• Merkel cells: Slowly adapting mechanoreceptors specialized for shape and edges.
• Meissner corpuscles: Rapidly adapting mechanoreceptors detecting flutter and low-frequency vibration.
• Pacinian corpuscles: Rapidly adapting mechanoreceptors specialized for high-frequency vibration.
• Dorsal columns: Pathways carrying touch, vibration, and proprioception.
• Medial lemniscus: Brainstem tract formed by decussated dorsal column fibers.
• Somatosensory cortex: Postcentral gyrus area processing tactile information.
• Cortical magnification: Enlarged cortical representation of regions like lips and fingertips.
• Astereognosis: Inability to identify objects by touch.
Chapter: General Physiology
Topic: Sensory Physiology
Subtopic: Two-point Discrimination
Lead Question – 2012
The distance by which two touch stimuli must be separated to be perceived as two separate stimuli is greatest at?
a) The lips
b) The palm of the hand
c) The back of scapula
d) The dorsum of the hand
Explanation: Two-point discrimination threshold is largest where receptive fields are big and cortical representation is small. Proximal trunk regions have poorest tactile acuity. Therefore, the greatest minimum separable distance is on the back of the scapula. Answer: c) The back of scapula.
Question 2
Which receptor type contributes most to high-resolution two-point discrimination on fingertips?
a) Pacinian corpuscles
b) Merkel discs
c) Ruffini endings
d) Free nerve endings
Explanation: Edges and fine form are encoded by slowly adapting type I mechanoreceptors with small receptive fields. Merkel cell–neurite complexes provide the highest spatial resolution for static touch and contribute most to two-point discrimination on fingertips and lips. Answer: b) Merkel discs.
Question 3
A patient with a hemisection of the spinal cord loses two-point discrimination below the lesion. Which tract is involved?
a) Spinothalamic tract
b) Dorsal column pathway
c) Spinocerebellar tract
d) Corticospinal tract
Explanation: A hemisection damaging dorsal columns impairs ipsilateral discriminative touch, vibration sense, and conscious proprioception below the lesion. Two-point discrimination on the affected side is markedly reduced, while pain and temperature may remain spared. Answer: b) Dorsal column pathway.
Question 4
Where is the two-point discrimination threshold smallest in the body?
a) Fingertips
b) Palm
c) Back
d) Abdomen
Explanation: Two-point thresholds are smallest where receptor density is highest and receptive fields are tiniest. Fingertips have abundant Merkel and Meissner endings plus strong cortical magnification, enabling exquisite spatial acuity. Therefore, minimum separable distance is least at fingertips. Answer: a) Fingertips.
Question 5
Which pathway carries discriminative touch and vibration sense to the brain?
a) Spinothalamic tract
b) Corticospinal tract
c) Dorsal column–medial lemniscus pathway
d) Spinoreticular tract
Explanation: Discriminative touch, vibration, and conscious proprioception ascend ipsilaterally in the dorsal columns to nucleus gracilis and cuneatus, then decussate as internal arcuate fibers to form the medial lemniscus. They project to thalamic VPL and somatosensory cortex. Answer: c) Dorsal column–medial lemniscus pathway.
Question 6
In which cortical region is two-point discrimination primarily resolved?
a) Prefrontal cortex
b) Primary somatosensory cortex
c) Insular cortex
d) Cerebellum
Explanation: Two-point discrimination is ultimately resolved in the primary somatosensory cortex on the postcentral gyrus, especially area 3b, exhibiting cortical magnification for hands and lips. Lesions there cause astereognosis and impaired tactile acuity contralaterally. Answer: b) Primary somatosensory cortex.
Question 7
A patient has loss of two-point discrimination on the left hand. Lesion is most likely in?
a) Right primary somatosensory cortex
b) Left motor cortex
c) Right cerebellum
d) Left dorsal root ganglion
Explanation: Somatosensory pathways decussate before reaching the cortex. Loss of discriminative touch from the left hand arises with a lesion in the contralateral somatosensory cortex. Answer: a) Right primary somatosensory cortex.
Question 8
Which phenomenon sharpens spatial resolution in two-point discrimination by inhibiting neighboring neurons?
a) Rebound excitation
b) Temporal summation
c) Lateral inhibition
d) Referred sensation
Explanation: Lateral inhibition enhances sensory contrast by suppressing responses in adjacent receptive fields. This improves spatial acuity and is fundamental for resolving two-point discrimination. Answer: c) Lateral inhibition.
Question 9
Which clinical sign indicates impaired cortical processing of tactile stimuli despite intact primary sensory pathways?
a) Hyperalgesia
b) Allodynia
c) Astereognosis
d) Hyperreflexia
Explanation: Patients with cortical lesions affecting parietal sensory areas cannot identify objects by touch despite preserved basic tactile sensation. This condition is astereognosis. Answer: c) Astereognosis.
Question 10
A lesion in which thalamic nucleus impairs two-point discrimination from the contralateral body?
a) VPL nucleus
b) Medial geniculate nucleus
c) VPM nucleus
d) Lateral geniculate nucleus
Explanation: The ventral posterolateral (VPL) nucleus of the thalamus receives medial lemniscus inputs carrying discriminative touch, vibration, and proprioception from the contralateral body. Lesions here impair two-point discrimination. Answer: a) VPL nucleus.
Question 11
Two-point discrimination is impaired but pain sensation remains intact. Which tract remains unaffected?
a) Spinothalamic tract
b) Dorsal column–medial lemniscus pathway
c) Corticospinal tract
d) Reticulospinal tract
Explanation: Preservation of pain sensation indicates an intact spinothalamic tract. Impairment of two-point discrimination indicates dorsal column dysfunction. Answer: a) Spinothalamic tract.
Chapter: Central Nervous System Physiology | Topic: Neuronal Membrane & Action Potential | Subtopic: Voltage-Gated Sodium Channels
Keywords
Voltage-gated sodium channels — proteins that open on depolarization allowing Na⁺ influx to initiate action potentials.
Axon initial segment (AIS) / Axon hillock — region where action potentials are usually initiated due to high Na⁺ channel density.
Nodes of Ranvier — gaps in myelin with concentrated Na⁺ channels enabling saltatory conduction.
Soma — neuronal cell body; integrates synaptic inputs but has lower Na⁺ channel density than AIS.
Dendrites — receive inputs and may have Na⁺ channels for back-propagation, but fewer than AIS.
Action potential threshold — lowest depolarization required to open sufficient Na⁺ channels to trigger spike.
Saltatory conduction — rapid impulse propagation between nodes of Ranvier in myelinated axons.
Ankyrin-G — scaffold protein essential for clustering Na⁺ channels at the axon initial segment.
Local anaesthetics — block voltage-gated Na⁺ channels to prevent action-potential propagation.
Channelopathies — disorders caused by mutations in sodium channel genes affecting excitability and causing seizures or paralysis.
Lead Question - 2012
Sodium channels are maximum in which part of neuron ?
a) Soma
b) Axon hillock
c) Dendrites
d) Axon
Explanation: The axon hillock (axon initial segment) has the highest density of voltage-gated sodium channels and is the usual trigger zone for action potentials. This high channel concentration, organized by ankyrin-G and associated scaffolds, lowers the threshold for spike initiation. Correct answer: b) Axon hillock.
Q1. Where along myelinated axons are sodium channels highly concentrated to enable saltatory conduction?
a) Internodal myelin
b) Nodes of Ranvier
c) Soma membrane
d) Dendritic spines
Explanation: Nodes of Ranvier are unmyelinated gaps densely populated with voltage-gated sodium channels. Action potentials are regenerated at these nodes, allowing rapid saltatory conduction down the axon. This arrangement increases conduction velocity and metabolic efficiency. Correct answer: b) Nodes of Ranvier.
Q2. Which scaffolding protein is essential for clustering sodium channels at the axon initial segment?
a) Ankyrin-G
b) Tubulin
c) Actin
d) Spectrin
Explanation: Ankyrin-G anchors voltage-gated sodium channels and other membrane proteins to the axon initial segment cytoskeleton, maintaining high local channel density necessary for action-potential initiation. Disruption of ankyrin-G disperses channels and reduces neuronal excitability. Correct answer: a) Ankyrin-G.
Q3. Local anaesthetics such as lidocaine produce analgesia primarily by blocking which channels?
a) Voltage-gated potassium channels
b) Voltage-gated sodium channels
c) Voltage-gated calcium channels
d) Ligand-gated chloride channels
Explanation: Local anaesthetics bind to and block voltage-gated sodium channels, preventing initiation and propagation of action potentials in sensory fibers. Small nociceptive fibers are preferentially blocked, producing loss of pain and temperature sensation. Correct answer: b) Voltage-gated sodium channels.
Q4. A mutation that reduces sodium-channel availability in the axon hillock would most likely cause:
a) Increased neuronal firing
b) Decreased excitability and possible weakness
c) Faster action potentials
d) Enhanced synaptic transmission
Explanation: Reduced sodium-channel availability at the axon initial segment raises the threshold for spike initiation, decreasing neuronal excitability and impairing signal transmission. Clinically this may cause muscle weakness, conduction block, or epileptic phenotypes depending on neuronal population affected. Correct answer: b) Decreased excitability and possible weakness.
Q5. Dendritic sodium channels support which physiological process relevant to synaptic plasticity?
a) Action-potential back-propagation
b) Neurotransmitter synthesis
c) Axonal myelination
d) Vesicle recycling
Explanation: Voltage-gated sodium channels in dendrites allow action potentials to back-propagate into the dendritic tree, modulating calcium entry and synaptic strength. This back-propagation contributes to spike-timing-dependent plasticity and learning. Correct answer: a) Action-potential back-propagation.
Q6. During the relative refractory period, why is a larger stimulus required to elicit an action potential?
a) All Na⁺ channels are permanently removed
b) Many Na⁺ channels are inactivated and K⁺ conductance is increased
c) Membrane potential is more positive than threshold
d) Synaptic inputs are inhibited
Explanation: After an action potential, a subset of Na⁺ channels remains inactivated and K⁺ channels remain open, hyperpolarizing the membrane; a stronger depolarizing input is thus required to reach threshold. This defines the relative refractory period. Correct answer: b) Many Na⁺ channels are inactivated and K⁺ conductance is increased.
Q7. Which feature increases axonal conduction velocity most effectively?
a) Decreasing axon diameter
b) Increasing myelination and axon diameter
c) Reducing Na⁺ channel density at nodes
d) Increasing internodal capacitance
Explanation: Larger axon diameter and increased myelination raise conduction velocity by reducing internal resistance and membrane capacitance. Adequate sodium-channel density at nodes is also required. Correct answer: b) Increasing myelination and axon diameter.
Q8. Which antiepileptic medication exerts effects by stabilizing the inactivated state of sodium channels?
a) Phenytoin
b) Levodopa
c) Fluoxetine
d) Propranolol
Explanation: Phenytoin binds voltage-gated sodium channels, prolonging their inactivated state and limiting repetitive firing of neurons. This mechanism reduces seizure propagation in many epilepsy syndromes. Correct answer: a) Phenytoin.
Q9. Which region is the most common site for initiation of spontaneous epileptic discharges due to high excitability?
a) Axon hillock / initial segment
b) Distal axon terminals
c) Soma nucleus
d) Myelin sheath
Explanation: The axon initial segment’s high density of sodium channels and low threshold make it a frequent locus for abnormal spontaneous discharges in epilepsy. Pathologic increases in excitability here can produce paroxysmal firing. Correct answer: a) Axon hillock / initial segment.
Q10. Which pathological process directly reduces sodium-channel clustering at the AIS leading to reduced excitability?
a) Mutation or loss of ankyrin-G
b) Increased myelination
c) Enhanced Na⁺ channel synthesis
d) Elevated extracellular potassium only
Explanation: Loss or dysfunction of ankyrin-G disrupts anchoring of sodium channels at the AIS, dispersing them and impairing action-potential initiation. This reduces neuronal excitability and can contribute to neurological disease. Correct answer: a) Mutation or loss of ankyrin-G.
Chapter: Central Nervous System Physiology | Topic: Hypothalamic Control | Subtopic: Thermoregulation and Shivering
Keywords
Thermoregulation — physiological processes that maintain core body temperature.
Preoptic area (POA) — hypothalamic region sensing temperature and coordinating heat-loss responses.
Posterior hypothalamus — activates heat-production mechanisms including shivering and sympathetic vasoconstriction.
Shivering — involuntary rhythmic skeletal muscle contractions generating heat under hypothalamic drive.
Warm-sensitive neurons — in POA; stimulate heat-loss (sweating, vasodilation).
Cold-sensitive pathways — activate posterior hypothalamus to produce heat via shivering and autonomic output.
Pyrogens — raise hypothalamic set point producing fever (distinct from hyperthermia).
Thermal effector organs — skeletal muscle (shivering), skin vessels (vasomotor), sweat glands.
Behavioral responses — seeking shelter/clothing under hypothalamic and cortical influence.
Clinical relevance — hypothalamic lesions can produce hypothermia or hyperthermia and loss of shivering.
Lead Question - 2012
Shivering is controlled by: (also in September 2012, March 2013)
a) Dorsomedial nucleus
b) Posterior hypothalamus
c) Perifornical nucleus
d) Lateral hypothalamic area
Explanation: Shivering—involuntary rhythmic skeletal muscle contractions that generate heat—is driven by cold-sensitive pathways activating the posterior hypothalamus. The posterior hypothalamic area orchestrates motor and sympathetic outputs for heat production. Therefore the correct answer is b) Posterior hypothalamus, responsible for shivering and thermogenic responses.
Q1. Lesion of the preoptic area typically causes:
a) Hypothermia
b) Hyperthermia
c) Diabetes insipidus
d) Hyperphagia
Explanation: The preoptic area contains warm-sensitive neurons initiating heat-loss responses. Lesioning it abolishes heat-dissipation, producing uncontrolled rise in body temperature (hyperthermia). Thus the correct answer is b) Hyperthermia. This differs from DI or appetite disturbances tied to other hypothalamic nuclei.
Q2. Fever differs from hyperthermia because fever results from:
a) Ambient heat overload
b) Raised hypothalamic set point due to pyrogens
c) Failure of sweating
d) Posterior hypothalamic lesion
Explanation: Fever arises when pyrogens raise the hypothalamic thermoregulatory set point, causing the body to conserve and generate heat until the new set point is reached. This distinguishes fever from hyperthermia, which is failure of heat loss. Correct answer: b).
Q3. Which hypothalamic area promotes heat production when activated by cold?
a) Anterior hypothalamus
b) Posterior hypothalamus
c) Suprachiasmatic nucleus
d) Arcuate nucleus
Explanation: Cold signals activate cold-sensitive afferents that stimulate the posterior hypothalamus to increase thermogenesis by shivering and sympathetic activation. The anterior (preoptic) area mediates heat loss. Correct answer: b) Posterior hypothalamus, which triggers heat-generating mechanisms.
Q4. Which effector mediates most rapid heat production in humans?
a) Brown adipose tissue
b) Shivering (skeletal muscle activity)
c) Increased thyroid secretion
d) Skin vasodilation
Explanation: Shivering produces immediate heat via rhythmic skeletal muscle contractions under posterior hypothalamic control, providing rapid thermogenesis. Brown adipose tissue contributes in infants, while thyroid changes and vasomotor adjustments are slower. Correct answer: b) Shivering.
Q5. Which sign indicates activation of heat-loss mechanisms?
a) Vasoconstriction
b) Shivering
c) Sweating and cutaneous vasodilation
d) Piloerection
Explanation: Heat-loss responses include sweating and cutaneous vasodilation mediated by preoptic area signals. These lower core temperature by evaporative cooling and increased skin blood flow. Correct answer: c) Sweating and cutaneous vasodilation, opposite to shivering which produces heat.
Q6. A patient with impaired shivering after hypothalamic surgery most likely had damage to:
a) Ventromedial nucleus
b) Posterior hypothalamus
c) Suprachiasmatic nucleus
d) Lateral hypothalamus
Explanation: Surgical damage to the posterior hypothalamus abolishes cold-induced shivering and some sympathetic thermogenic responses. Therefore impaired shivering after hypothalamic surgery suggests posterior hypothalamic injury. Correct answer: b) Posterior hypothalamus.
Q7. Which autonomic response accompanies shivering to preserve core temperature?
a) Cutaneous vasodilation
b) Cutaneous vasoconstriction
c) Diaphoresis
d) Increased salivation
Explanation: To conserve heat during shivering, sympathetic-mediated cutaneous vasoconstriction reduces blood flow to the skin, minimizing heat loss. This complements muscular heat production. Correct answer: b) Cutaneous vasoconstriction.
Q8. Which hypothalamic nucleus is the master clock for circadian temperature rhythm?
a) Suprachiasmatic nucleus (SCN)
b) Paraventricular nucleus
c) Dorsomedial nucleus
d) Lateral hypothalamus
Explanation: The suprachiasmatic nucleus (SCN) entrains circadian rhythms including daily fluctuations in body temperature by signaling other hypothalamic areas. Lesions disrupt rhythmic temperature variations. Correct answer: a) Suprachiasmatic nucleus (SCN).
Q9. Which pharmacologic agent can reduce shivering by central action?
a) Acetaminophen (paracetamol)
b) Meperidine (pethidine)
c) Epinephrine
d) Dobutamine
Explanation: Meperidine centrally suppresses shivering via opioid and α2-adrenergic effects in the hypothalamus and brainstem. It is used to treat postoperative shivering. Correct answer: b) Meperidine (pethidine).
Q10. In hypothermia, which behavioral response is initiated by cortical and hypothalamic centers?
a) Removing clothing
b) Seeking warmth and adding clothing
c) Inducing sweat
d) Increasing water intake
Explanation: Behavioral thermoregulation includes seeking warmth and adding clothing to reduce heat loss; these actions are driven by hypothalamic signals integrated with cortical decision-making. Correct answer: b) Seeking warmth and adding clothing.
Chapter: Central Nervous System Physiology | Topic: Hypothalamic Functions | Subtopic: Preoptic Area & Homeostasis
Keyword Definitions
Preoptic nucleus — hypothalamic region with warm-sensitive neurons controlling heat-loss responses.
Thermoregulation — physiological processes maintaining core temperature via autonomic and behavioral responses.
Hyperthermia — abnormally high body temperature due to failed heat dissipation or excessive heat production.
Hyperphagia — excessive eating driven by hypothalamic or metabolic disturbances.
Hyperdipsia — excessive thirst and fluid intake, often osmotic or hypothalamic in origin.
Homeostasis — coordinated regulation of internal milieu (temperature, thirst, hunger, endocrine balance).
Autonomic output — hypothalamic control of sympathetic and parasympathetic tone influencing temperature and metabolism.
POA lesions — can disrupt fever responses, thermoregulatory set points, and heat-loss mechanisms.
Fever vs hyperthermia — fever raises set point via pyrogens; hyperthermia is failure of dissipation.
Clinical relevance — hypothalamic injury, stroke, tumors can produce dysautonomia and temperature dysregulation.
Lead Question - 2012
Lesion of preoptic nucleus of hypothalamus causes?
a) Hyperphagia
b) Hyperdypsia
c) Hyperthermia
d) Hyperglycemia
Explanation: The preoptic area contains warm-sensitive neurons that initiate heat-loss responses (vasodilation, sweating). Lesioning these neurons abolishes heat-loss mechanisms, producing uncontrolled rise in body temperature (hyperthermia). This is not primarily a feeding or thirst center. Correct answer: c) Hyperthermia.
Q1. Damage to the lateral hypothalamic area typically causes:
a) Anorexia
b) Hyperphagia
c) Polydipsia
d) Hypothermia
Explanation: The lateral hypothalamus is the feeding (hunger) center; lesions produce anorexia and weight loss, while stimulation causes hyperphagia. Thus damage causes lack of eating rather than increased appetite. Correct answer: a) Anorexia (lesion → anorexia; stimulation → hyperphagia).
Q2. A lesion of the supraoptic nucleus would most likely produce:
a) Diabetes insipidus (polyuria, polydipsia)
b) Cushing’s syndrome
c) Hyperthermia
d) Adipsia
Explanation: The supraoptic nucleus produces vasopressin (ADH); damage causes central diabetes insipidus with polyuria and compensatory polydipsia. This is a classic hypothalamic endocrine deficit. Correct answer: a) Diabetes insipidus (polyuria, polydipsia).
Q3. Which hypothalamic lesion produces hyperphagia and obesity in animals?
a) Ventromedial nucleus lesion
b) Lateral hypothalamic lesion
c) Preoptic lesion
d) Suprachiasmatic lesion
Explanation: The ventromedial hypothalamus is a satiety center; lesions remove restraining signals leading to hyperphagia and obesity. Lateral lesions cause anorexia. Correct answer: a) Ventromedial nucleus lesion.
Q4. Destruction of the suprachiasmatic nucleus (SCN) leads to:
a) Loss of circadian rhythms
b) Hyperthermia
c) Polyphagia
d) Diabetes insipidus
Explanation: The SCN is the master circadian pacemaker; lesions disrupt sleep-wake, hormonal, and temperature rhythms. This abolishes regular circadian patterns but does not directly cause fever or thirst disorders. Correct answer: a) Loss of circadian rhythms.
Q5. Fever (pyrogen-mediated) differs from hyperthermia because fever involves:
a) Raised hypothalamic set point
b) Failure of heat dissipation
c) Ambient heat overload
d) Direct injury to preoptic neurons
Explanation: Fever results from pyrogens raising the hypothalamic thermostat (set point), inducing chills and thermoregulatory defenses to reach the new set point. Hyperthermia is failure of heat loss without set-point change. Correct answer: a) Raised hypothalamic set point.
Q6. A patient with hypothalamic lesion presents with persistent hyperphagia and rage; which nucleus is likely affected?
a) Ventromedial nucleus
b) Preoptic nucleus
c) Paraventricular nucleus
d) Lateral hypothalamic area
Explanation: Ventromedial nucleus lesions remove satiety signals causing hyperphagia and aggression (sham rage). The lateral hypothalamus promotes feeding when stimulated. Paraventricular lesions affect autonomic and endocrine outputs. Correct answer: a) Ventromedial nucleus.
Q7. Lesion of preoptic area interferes with which autonomic thermoregulatory response?
a) Sweating and cutaneous vasodilation
b) Salivation
c) Pupillary constriction
d) Gastrointestinal motility
Explanation: The preoptic area triggers heat-loss responses such as sweating and vasodilation. Lesions abolish these mechanisms, leading to impaired heat dissipation and hyperthermia. Other autonomic functions are mediated by different hypothalamic regions. Correct answer: a) Sweating and cutaneous vasodilation.
Q8. Paraventricular nucleus (PVN) lesions primarily affect:
a) Oxytocin and CRH release influencing endocrine and autonomic functions
b) Visual processing
c) Primary motor control
d) Vestibular reflexes
Explanation: PVN neurons produce CRH and oxytocin and modulate sympathetic outflow; lesions disrupt HPA axis regulation and autonomic balance. This leads to endocrine and autonomic dysfunction rather than direct motor or visual deficits. Correct answer: a).
Q9. Central fever after hypothalamic hemorrhage is due to:
a) Disruption of preoptic heat-loss neurons
b) Bacterial infection
c) Peripheral inflammation only
d) Increased sweating
Explanation: Hypothalamic injury can cause central fever by damaging preoptic/POA neurons that mediate heat loss and set-point regulation; this produces sustained hyperthermia without infection. Correct answer: a) Disruption of preoptic heat-loss neurons.
Q10. A lesion of arcuate nucleus would most likely cause:
a) Disordered appetite regulation and altered GnRH/release control
b) Loss of temperature sensation
c) Loss of visual fields
d) Cerebellar ataxia
Explanation: The arcuate nucleus integrates peripheral metabolic signals (leptin, ghrelin) and influences appetite, prolactin and GnRH modulation. Lesions disrupt feeding and reproductive hormone regulation. It is not primarily involved in temperature sensation or motor coordination. Correct answer: a).
Chapter: Sensory Physiology | Topic: Visual Transduction | Subtopic: Photoreceptor Proteins
Keywords
Transducin — a heterotrimeric G-protein in photoreceptor cells involved in phototransduction.
Rhodopsin — light-sensitive pigment in rod outer segments that activates transducin.
Phototransduction — process converting photon absorption into electrical signals in retina.
cGMP phosphodiesterase — enzyme activated by transducin to lower cGMP and hyperpolarize photoreceptors.
Rods and cones — retinal photoreceptors for scotopic and photopic vision respectively.
Retinal — chromophore (11-cis-retinal) that changes conformation on photon absorption.
Hyperpolarization — photoreceptor response to light due to decreased cGMP-gated current.
Dark current — inward Na⁺/Ca²⁺ current in photoreceptors maintained by cGMP.
Visual cycle — enzymatic regeneration of 11-cis-retinal in retinal pigment epithelium.
G-protein coupled receptor (GPCR) — rhodopsin is a GPCR that activates transducin.
Lead Question - 2012
Transducin is a protein found in:
a) Glomerulus
b) Retina
c) Skeletal muscle
d) Adrenal medulla
Explanation: Transducin is a G-protein located in photoreceptor outer segments of the retina; it couples activated rhodopsin to cGMP phosphodiesterase. Upon photon capture transducin activates PDE, lowers cGMP, closes cGMP-gated channels and hyperpolarizes the photoreceptor. Correct answer: b) Retina.
Q1. Which pigment initiates phototransduction by activating transducin?
a) Hemoglobin
b) Melanin
c) Rhodopsin
d) Opsin in kidney
Explanation: Rhodopsin in rod outer segments absorbs photons, isomerizes 11-cis-retinal to all-trans-retinal, and activates the GPCR rhodopsin which then activates transducin, initiating the phototransduction cascade. Correct answer: c) Rhodopsin.
Q2. Activation of transducin leads directly to activation of which enzyme?
a) Adenylate cyclase
b) cGMP phosphodiesterase
c) Na⁺/K⁺ ATPase
d) Phospholipase C
Explanation: Activated transducin (Gαt) stimulates cGMP phosphodiesterase, decreasing cytoplasmic cGMP, closing cGMP-gated cation channels and hyperpolarizing photoreceptors. This is central to light signal transduction. Correct answer: b) cGMP phosphodiesterase.
Q3. Photoreceptor response to light is a:
a) Depolarization
b) Hyperpolarization
c) Action potential firing
d) No change
Explanation: Light activation leads to reduced cGMP, closure of cGMP-gated Na⁺ channels, decreased inward dark current and membrane hyperpolarization of photoreceptors. This graded hyperpolarization reduces glutamate release. Correct answer: b) Hyperpolarization.
Q4. Which retinal cells regenerate 11-cis-retinal as part of the visual cycle?
a) Müller glia
b) Retinal pigment epithelium (RPE)
c) Ganglion cells
d) Bipolar cells
Explanation: The retinal pigment epithelium (RPE) performs enzymatic steps to convert all-trans-retinal back to 11-cis-retinal, replenishing the chromophore for photopigments. This visual cycle is essential for sustained phototransduction. Correct answer: b) Retinal pigment epithelium (RPE).
Q5. Which photoreceptors primarily use transducin in their signal cascade?
a) Rods
b) Cones
c) Ganglion photoreceptors only
d) Both rods and cones
Explanation: Both rods and cones possess phototransduction cascades that employ G-proteins homologous to transducin (rod transducin Gαt1, cone transducins Gαt2), so both use transducin-like proteins to activate PDE. Correct answer: d) Both rods and cones.
Q6. A defect in transducin function would most likely cause:
a) Color blindness only
b) Night blindness and impaired phototransduction
c) Loss of accommodation
d) Elevated intraocular pressure
Explanation: Impaired transducin prevents effective activation of PDE, blunting photoreceptor hyperpolarization and reducing sensitivity, particularly affecting scotopic (rod-mediated) vision, causing night blindness and phototransduction defects. Correct answer: b) Night blindness and impaired phototransduction.
Q7. Which event follows activation of cGMP phosphodiesterase in photoreceptors?
a) Increased intracellular cGMP
b) Closure of cGMP-gated cation channels
c) Increased glutamate release
d) Depolarization
Explanation: PDE lowers cGMP levels, resulting in closure of cGMP-gated Na⁺/Ca²⁺ channels, decreased inward current and reduced glutamate release due to photoreceptor hyperpolarization. Correct answer: b) Closure of cGMP-gated cation channels.
Q8. Which molecule directly undergoes photoisomerization to start phototransduction?
a) 11-cis-retinal
b) Opsin protein backbone
c) cGMP
d) Transducin
Explanation: The chromophore 11-cis-retinal within rhodopsin photoisomerizes to all-trans-retinal upon photon absorption, changing rhodopsin conformation and activating transducin, initiating the cascade. Correct answer: a) 11-cis-retinal.
Q9. Which test assesses rod (scotopic) function most directly?
a) Photopic visual acuity
b) Dark adaptation test
c) Color vision test
d) Pupillary light reflex
Explanation: Dark adaptation measures recovery of visual sensitivity in low light, reflecting rod photoreceptor and transducin-PDE cascade function. Delayed or impaired dark adaptation suggests rod/transducin pathway dysfunction. Correct answer: b) Dark adaptation test.
Q10. Which class of receptors does rhodopsin belong to?
a) Ligand-gated ion channel
b) Tyrosine kinase receptor
c) G-protein coupled receptor (GPCR)
d) Nuclear receptor
Explanation: Rhodopsin is a GPCR embedded in photoreceptor membranes; upon photon-induced conformational change it activates transducin (a G-protein), classifying rhodopsin as a light-activated GPCR. Correct answer: c) G-protein coupled receptor (GPCR).
Chapter: Central Nervous System Physiology
Topic: Nerve Fibers and Conduction
Subtopic: Sensitivity to Pressure and Hypoxia
Keyword Definitions:
• Nerve Fibers: Axons classified based on diameter, conduction velocity, and function (A, B, C fibers).
• A Fibers: Large, myelinated fibers with rapid conduction, subdivided into alpha, beta, gamma, delta.
• B Fibers: Small, myelinated preganglionic autonomic fibers.
• C Fibers: Small, unmyelinated fibers, slow conduction, pain and temperature transmission.
• Hypoxia Sensitivity: Vulnerability of fibers to oxygen deprivation.
• Pressure Sensitivity: Susceptibility of fibers to mechanical compression.
• Neuropraxia: Temporary conduction block often due to compression.
• Paresthesia: Abnormal tingling or numb sensation due to nerve dysfunction.
Lead Question - 2012
A man slept with head over forearm, next morning he complains of tingling, numbness over forearm. It is caused by?
a) Sensitivity to hypoxia is A > B > C
b) Sensitivity to pressure is A > B > C
c) Sensitivity to hypoxia is C > B > A
d) Sensitivity to pressure is B > A > C
Explanation: Large myelinated A fibers are more susceptible to compression due to their size and myelin sheath. This explains temporary numbness or tingling after sleeping on a limb. Small unmyelinated C fibers are more resistant. Hence, sensitivity to pressure is A > B > C. Answer: b) Sensitivity to pressure is A > B > C
--- Guessed Question 1
Which nerve fibers are most sensitive to hypoxia?
a) A fibers
b) B fibers
c) C fibers
d) All equally
Explanation: Unmyelinated C fibers require continuous metabolic support and are highly sensitive to hypoxia. In oxygen deprivation, C fibers lose function first, causing early loss of pain and temperature sensation. Answer: c) C fibers
--- Guessed Question 2
Temporary conduction block without axonal damage due to compression is termed:
a) Axonotmesis
b) Neurotmesis
c) Neuropraxia
d) Wallerian degeneration
Explanation: Neuropraxia is a transient conduction block due to mechanical compression, as in the case of sleeping on an arm. Recovery is complete within days to weeks as no axonal damage occurs. Answer: c) Neuropraxia
--- Guessed Question 3
Which type of fibers mediate burning pain?
a) A alpha
b) A beta
c) A delta
d) C fibers
Explanation: Burning, dull, poorly localized pain is transmitted by unmyelinated C fibers. A delta fibers carry sharp, pricking pain. Thus, chronic tingling or burning after compression is mediated by C fibers. Answer: d) C fibers
--- Guessed Question 4
Which fibers are blocked earliest by local anesthetics?
a) A alpha
b) A delta
c) B fibers
d) C fibers
Explanation: Small, myelinated B fibers (preganglionic autonomic) are most sensitive to local anesthetics, followed by C fibers, then A delta, and lastly large motor A alpha fibers. Answer: c) B fibers
--- Guessed Question 5
Patient develops numbness after tight bandage. Most likely affected fibers are:
a) A fibers
b) B fibers
c) C fibers
d) None
Explanation: Mechanical compression preferentially affects large myelinated A fibers, leading to numbness and weakness. Unmyelinated C fibers remain relatively preserved. Answer: a) A fibers
--- Guessed Question 6
Which sensation is first affected during hypoxia?
a) Pain
b) Touch
c) Autonomic functions
d) Vibration
Explanation: Pain is mediated by C fibers, which are highly hypoxia-sensitive. Thus, pain sensation is often first impaired in hypoxic conditions. Answer: a) Pain
--- Guessed Question 7
Compression of radial nerve during deep sleep leads to:
a) Wrist drop
b) Foot drop
c) Claw hand
d) Facial palsy
Explanation: Radial nerve palsy due to compression in sleep ("Saturday night palsy") leads to weakness of wrist extensors, manifesting as wrist drop. Answer: a) Wrist drop
--- Guessed Question 8
Which nerve fiber type has the slowest conduction velocity?
a) A alpha
b) A beta
c) B fibers
d) C fibers
Explanation: Unmyelinated C fibers have the slowest conduction velocity (~0.5–2 m/s) compared to fast-conducting A alpha fibers (~100 m/s). Answer: d) C fibers
--- Guessed Question 9
Which fibers are most pressure-sensitive clinically leading to tingling?
a) A fibers
b) B fibers
c) C fibers
d) All equally
Explanation: Large, heavily myelinated A fibers are most pressure-sensitive, hence tingling and numbness are due to their dysfunction. Answer: a) A fibers
--- Guessed Question 10
Loss of touch and vibration but preserved pain after compression indicates damage to:
a) A alpha and beta fibers
b) A delta fibers
c) C fibers
d) B fibers
Explanation: Touch and vibration are carried by large A alpha and A beta fibers, which are most pressure-sensitive. C fibers carrying pain remain intact initially, explaining preserved pain sensation. Answer: a) A alpha and beta fibers
Chapter: Peripheral Nerve Physiology | Topic: Nociception & Pain Fibres | Subtopic: Sensory Fiber Types
Keywords
Peripheral nociceptors — sensory receptors that signal tissue-damaging stimuli.
Aδ fibres — thin myelinated fibres conducting fast sharp pain.
C fibres — small unmyelinated fibres conducting slow burning/dull pain.
Aβ fibres — large myelinated fibres for touch and vibration, not primary nociception.
Conduction velocity — speed of action potential propagation determined by diameter and myelination.
Spinothalamic tract — ascending pathway transmitting pain and temperature to thalamus.
Substance P / CGRP — neuropeptides released by nociceptors mediating pain and neurogenic inflammation.
Gate control theory — modulation of pain by non-nociceptive afferents at spinal level.
Central sensitization — heightened dorsal horn responsiveness after persistent nociceptive input.
Local anaesthetics — block sodium channels, preferentially affecting small diameter fibres first.
Lead Question - 2012
Burning pain is carried by which type of fibres ?
a) A alpha
b) A delta
c) A beta
d) C
Explanation: Burning, slow, poorly localized pain is typically transmitted by small unmyelinated C fibres that conduct at low velocity and carry polymodal nociceptive input. Aδ fibres convey fast sharp pain. Therefore the correct answer is d) C. C-fibre activity also mediates neurogenic inflammation via Substance P and CGRP.
Q1. Fast, well-localized sharp pain (first pain) is carried mainly by:
a) A alpha
b) A delta
c) C fibres
d) A beta
Explanation: First, sharp pain is mediated by thinly myelinated Aδ fibres that have higher conduction velocity than C fibres and project through the spinothalamic tract to somatosensory cortex, producing rapid, localized pain sensations. Hence the correct answer is b) A delta.
Q2. Which fibres primarily transmit touch and vibration?
a) A beta
b) C fibres
c) A delta
d) A gamma
Explanation: Large myelinated Aβ fibres carry discriminative touch, pressure, and vibration information via the dorsal column–medial lemniscal pathway. They are not primary nociceptors. Correct answer: a) A beta. Activation of Aβ fibres can modulate pain via gate control mechanisms in the dorsal horn.
Q3. Which ascending pathway carries pain and temperature to the brain?
a) Dorsal columns
b) Spinothalamic tract
c) Corticospinal tract
d) Spinocerebellar tract
Explanation: The anterolateral system, chiefly the spinothalamic tract, transmits nociceptive and thermoreceptive signals from spinal cord to thalamus and cortex. Dorsal columns carry vibration and proprioception. Correct answer: b) Spinothalamic tract.
Q4. Which neuropeptide released from nociceptors contributes to neurogenic inflammation?
a) GABA
b) Substance P
c) Dopamine
d) Serotonin
Explanation: Substance P and CGRP released from peripheral terminals of C fibres promote vasodilation, plasma extravasation, and immune cell recruitment, producing neurogenic inflammation and sensitization. This augments pain. Correct answer: b) Substance P.
Q5. Local anaesthetics block which channels to prevent nociception?
a) Calcium channels
b) Sodium channels
c) Potassium channels
d) Chloride channels
Explanation: Local anaesthetics inhibit voltage-gated sodium channels, preventing action potential initiation and propagation in sensory fibres. Small-diameter unmyelinated C and thin myelinated Aδ fibres are blocked preferentially, producing analgesia. Correct answer: b) Sodium channels.
Q6. Which clinical sign suggests small fibre (C/Aδ) neuropathy?
a) Loss of vibration sense
b) Burning distal pain with preserved reflexes
c) Pure motor weakness
d) Loss of proprioception
Explanation: Small-fibre neuropathy causes burning, shooting pain and dysesthesias in a distal stocking distribution with relatively preserved muscle strength and large-fibre modalities like vibration. Reflexes may be normal early. Correct answer: b) Burning distal pain with preserved reflexes.
Q7. Gate control theory proposes that activation of which fibres inhibits pain transmission?
a) C fibres
b) A beta fibres
c) A delta fibres
d) Sympathetic efferents
Explanation: Large-diameter Aβ fibres carrying touch input activate inhibitory interneurons in dorsal horn, reducing transmission from nociceptive Aδ/C fibres to projection neurons. This underlies analgesic effects of rubbing or TENS. Correct answer: b) A beta fibres.
Q8. Central sensitization results in which clinical phenomenon?
a) Hypoalgesia
b) Allodynia (pain to non-painful stimuli)
c) Loss of reflexes
d) Improved proprioception
Explanation: Persistent nociceptive input induces dorsal horn hyperexcitability and synaptic plasticity, producing allodynia and hyperalgesia where innocuous stimuli become painful. This is central sensitization seen in chronic pain syndromes. Correct answer: b) Allodynia.
Q9. Which fibre type has the slowest conduction velocity?
a) A alpha
b) A beta
c) A delta
d) C fibres
Explanation: Unmyelinated C fibres have the smallest diameter and slowest conduction velocity (~0.5–2 m/s), mediating slow burning pain and autonomic reflexes. Aα/Aβ are fastest. Correct answer: d) C fibres.
Q10. Which analgesic mechanism involves opioid receptors in the dorsal horn?
a) NSAID inhibition of COX
b) Activation of μ-opioid receptors reducing neurotransmitter release
c) Local anaesthetic sodium channel block
d) TRPV1 activation
Explanation: Opioids bind μ receptors on presynaptic nociceptive terminals and postsynaptic dorsal horn neurons, inhibiting substance P release and hyperpolarizing neurons, reducing pain transmission centrally. This is a principal mechanism for strong analgesics. Correct answer: b) Activation of μ-opioid receptors.
Chapter: Central Nervous System Physiology
Topic: Cerebrospinal Fluid (CSF)
Subtopic: Biochemical Properties of CSF
Keyword Definitions:
• CSF: Clear fluid in brain and spinal cord providing cushioning and nutrient exchange.
• Plasma: Liquid component of blood carrying cells, proteins, and nutrients.
• CSF/Plasma Glucose Ratio: A diagnostic marker comparing CSF glucose levels to plasma glucose.
• Blood-Brain Barrier: Selective barrier regulating passage of substances into CSF.
• Meningitis: Inflammation of meninges often causing altered CSF glucose.
• Hypoglycorrhachia: Abnormally low CSF glucose, seen in infections and tumors.
• Hyperglycemia: High plasma glucose leading to proportionally higher CSF glucose.
• CSF Analysis: Laboratory test to evaluate neurological diseases.
Lead Question - 2012
CSF/plasma glucose ratio is ?
a) 0.2 - 0.4
b) 0.6 - 0.8
c) 1.2 - 1.6
d) 1.6 - 2.2
Explanation: The normal CSF/plasma glucose ratio is about 0.6 to 0.8. CSF glucose is typically two-thirds of plasma glucose. Reduced ratios occur in bacterial and TB meningitis, while viral meningitis usually maintains normal values. Answer: b) 0.6 - 0.8
--- Guessed Question 1
In bacterial meningitis, the CSF/plasma glucose ratio is usually:
a) Normal
b) Increased
c) Decreased
d) Unchanged
Explanation: Bacterial meningitis reduces CSF glucose due to bacterial metabolism. The CSF/plasma glucose ratio often falls below 0.4. This is a key diagnostic indicator. Answer: c) Decreased
--- Guessed Question 2
Which CSF finding is most suggestive of tuberculous meningitis?
a) Normal CSF glucose
b) CSF glucose ↓
c) CSF protein normal
d) No pleocytosis
Explanation: Tuberculous meningitis shows markedly reduced glucose, elevated proteins, and lymphocytic pleocytosis. This pattern helps distinguish it from viral meningitis. Answer: b) CSF glucose ↓
--- Guessed Question 3
A patient with viral meningitis is most likely to show which CSF/plasma glucose ratio?
a) 0.6 - 0.8
b) c) >1.0
d) 0.2
Explanation: Viral meningitis does not significantly affect CSF glucose, so the CSF/plasma ratio remains in the normal range of 0.6–0.8. Answer: a) 0.6 - 0.8
--- Guessed Question 4
Which condition most commonly causes low CSF glucose with elevated protein and lymphocytes?
a) Viral meningitis
b) Tuberculous meningitis
c) Subarachnoid hemorrhage
d) Normal pressure hydrocephalus
Explanation: Tuberculous meningitis typically presents with low glucose, high protein, and lymphocytic predominance. Answer: b) Tuberculous meningitis
--- Guessed Question 5
Increased CSF glucose compared to plasma is seen in:
a) Hyperglycemia
b) Hypoglycemia
c) Meningitis
d) None
Explanation: CSF glucose reflects plasma levels. In hyperglycemia, CSF glucose increases but more slowly, keeping the ratio near normal. Answer: a) Hyperglycemia
--- Guessed Question 6
CSF/plasma glucose ratio helps primarily in diagnosis of:
a) Epilepsy
b) Stroke
c) Meningitis
d) Brain tumor
Explanation: The ratio is mainly valuable in meningitis. Bacterial and TB meningitis reduce the ratio, while viral meningitis keeps it normal. Answer: c) Meningitis
--- Guessed Question 7
A lumbar puncture shows CSF glucose 20 mg/dl, plasma glucose 100 mg/dl. What is the CSF/plasma ratio?
a) 0.2
b) 0.5
c) 0.8
d) 1.2
Explanation: Ratio = 20/100 = 0.2, which is abnormally low. This strongly suggests bacterial or TB meningitis. Answer: a) 0.2
--- Guessed Question 8
In which condition is CSF glucose usually normal?
a) Viral meningitis
b) Bacterial meningitis
c) TB meningitis
d) Fungal meningitis
Explanation: Viral meningitis maintains normal CSF glucose, unlike bacterial, TB, or fungal meningitis which lower glucose levels. Answer: a) Viral meningitis
--- Guessed Question 9
Which barrier controls glucose entry into CSF?
a) Meninges
b) Blood-brain barrier
c) Pia mater
d) Dural venous sinuses
Explanation: The blood-brain barrier regulates glucose entry into CSF by selective transport, ensuring stable CSF composition. Answer: b) Blood-brain barrier
--- Guessed Question 10
A patient with suspected bacterial meningitis has a CSF/plasma ratio of 0.3. What additional CSF finding is expected?
a) Low protein
b) Neutrophilic pleocytosis
c) Eosinophilia
d) Normal cell count
Explanation: Bacterial meningitis typically shows low glucose, high protein, and neutrophilic pleocytosis. This triad is highly diagnostic. Answer: b) Neutrophilic pleocytosis
Chapter: Central Nervous System | Topic: Visual Recognition | Subtopic: Face Perception & Agnosias
Keywords
Prosopagnosia — inability to recognize familiar faces despite intact vision.
Fusiform face area (FFA) — region in inferior temporal cortex specialized for face recognition.
Associative visual agnosia — failure to assign meaning to perceived objects despite intact perception.
Apperceptive agnosia — impaired object perception (shape/form) with intact elementary vision.
Right occipitotemporal cortex — often dominant for facial recognition tasks.
Visual associative cortex — links visual percepts to memory and meaning.
Alexia — loss of reading; can be visual-associative if cortex involved.
Topographic agnosia — inability to recognize familiar places/landmarks.
CFD (capgras) — delusional misidentification where face is recognized but person is believed to be impostor.
Face processing stream — ventral occipitotemporal pathway for object/face identification.
Lead Question - 2012
Pt. is able to recognise person by name but not by face. Lesion is in ?
a) Post parietal region
b) Occipital
c) Frontal lobe
d) Temporal lobe
Explanation: Inability to recognize faces (prosopagnosia) with preserved verbal identification indicates damage to the face-processing region — the fusiform face area in the inferior temporal (occipitotemporal) cortex, typically the right temporal lobe. Thus the correct answer is (d) Temporal lobe. This spares name retrieval via language networks.
Q2. Classic prosopagnosia most commonly results from lesion in which area?
a) Dorsal parietal cortex
b) Fusiform gyrus (inferior temporal)
c) Primary visual cortex (V1)
d) Broca’s area
Explanation: Acquired prosopagnosia typically follows lesions in the fusiform gyrus (inferior temporal/occipitotemporal region), especially on the right. The FFA processes holistic face information; damage disrupts face identity recognition while leaving basic vision and language intact. Correct answer: (b) Fusiform gyrus.
Q3. A patient sees an object but cannot name it though can describe its use. This suggests:
a) Apperceptive visual agnosia
b) Associative visual agnosia
c) Cortical blindness
d) Visual neglect
Explanation: Associative visual agnosia occurs when perceptual processing is adequate but the link to semantic knowledge is disrupted, so patients can describe object use but cannot name it. This localizes to higher-order ventral stream cortical areas. Correct answer: (b) Associative visual agnosia.
Q4. Which deficit indicates right occipitotemporal dysfunction rather than primary visual loss?
a) Hemianopia with macular sparing
b) Prosopagnosia with normal acuity
c) Complete blindness
d) Visual field neglect
Explanation: Prosopagnosia with preserved visual acuity and fields suggests cortical processing impairment in the right occipitotemporal region (FFA) rather than primary visual cortex damage. Hemianopia indicates V1 lesions; neglect implicates parietal cortex. Correct answer: (b).
Q5. Developmental (congenital) prosopagnosia is best characterized by:
a) Later-life stroke causing face blindness
b) Lifelong difficulty recognizing faces with normal IQ
c) Visual acuity loss from birth
d) Progressive dementia
Explanation: Developmental prosopagnosia presents from early life as a selective deficit in face recognition despite normal vision, intelligence, and no structural lesion. Patients rely on voice or context. Correct answer: (b). It reflects functional differences in face-processing networks.
Q6. Capgras syndrome differs from prosopagnosia because patients:
a) Cannot see faces
b) Recognize faces but believe they are impostors
c) Name faces accurately
d) Have primary visual loss
Explanation: In Capgras delusion, patients perceive faces and may name them but lack the normal affective familiarity, leading to belief that a known person is an impostor — a disconnection between recognition and emotional response. Correct answer: (b).
Q7. Which test best assesses prosopagnosia clinically?
a) Visual acuity chart
b) Benton Facial Recognition Test
c) Pupillary light reflex
d) Snellen chart
Explanation: The Benton Facial Recognition Test evaluates face perception and matching without requiring naming, useful to detect prosopagnosia. Visual acuity tests do not assess identity recognition. Correct answer: (b). Neuropsychological testing localizes processing deficits.
Q8. A lesion producing alexia without agraphia involves the visual word form area and typically spares:
a) Right inferior temporal lobe
b) Language output areas (e.g., Broca’s)
c) Primary visual cortex exclusively
d) Auditory comprehension
Explanation: Alexia without agraphia results from left occipitotemporal (visual word form area) lesions with intact language cortex, so patients can write but not read. It demonstrates modality-specific visual-associative deficits. Correct answer: (b).
Q9. Which hemisphere is more commonly dominant for face recognition in most right-handed people?
a) Left hemisphere
b) Right hemisphere
c) Both equally
d) Brainstem
Explanation: The right occipitotemporal region is typically dominant for holistic face processing in right-handed individuals; right-sided lesions more often produce prosopagnosia. Left-sided lesions can impair aspects of facial recognition but less commonly. Correct answer: (b) Right hemisphere.
Q10. Which rehabilitation strategy may help a patient with prosopagnosia?
a) Visual acuity correction only
b) Training to use non-face cues (voice, gait, context)
c) Surgical removal of fusiform gyrus
d) High-dose steroids
Explanation: Compensation training teaches reliance on non-facial cues (voice, clothing, context, unique features) to identify people, improving functioning despite persistent cortical deficit. There is no surgical or steroid cure for most acquired prosopagnosia. Correct answer: (b).
Q11. In a patient who recognizes names but not faces, which imaging finding is most likely?
a) Infarct in right inferior occipitotemporal cortex
b) Bilateral frontal lobe atrophy
c) Lesion of primary visual cortex
d) Left cerebellar infarct
Explanation: MRI showing a focal lesion or infarct in the right inferior occipitotemporal (fusiform) cortex fits classical acquired prosopagnosia with preserved language-based name recognition. Primary V1 lesions cause field defects, while frontal or cerebellar lesions produce different syndromes. Correct answer: (a).
Chapter: Autonomic Nervous System | Topic: Peripheral Autonomic Ganglia | Subtopic: Sympathetic Ganglia
Keywords
Sympathetic ganglia — clusters of postganglionic neuronal cell bodies in the sympathetic chain and prevertebral plexuses.
Multipolar neuron — neuron with one axon and multiple dendrites; typical of autonomic ganglia.
Preganglionic fiber — myelinated B fiber from thoracolumbar spinal cord that synapses in ganglia.
Postganglionic fiber — unmyelinated C fiber projecting to effector organs.
Neurotransmitters — acetylcholine (preganglionic); norepinephrine (postganglionic) for most sympathetic targets.
Paravertebral chain — bilateral sympathetic trunk alongside vertebral column.
Prevertebral ganglia — celiac, superior and inferior mesenteric ganglia supplying abdominal viscera.
Visceral reflexes — autonomic reflex arcs involving pre- and postganglionic neurons.
Chromaffin cells — adrenal medulla cells acting like sympathetic postganglionic neurons (release catecholamines into blood).
Autonomic dysreflexia — exaggerated sympathetic response seen with high spinal cord injury.
Lead Question - 2012
Neurons in sympathetic ganglia are ?
a) Unipolar
b) Bipolar
c) Pseudounipolar
d) Multipolar
Explanation: Sympathetic (autonomic) ganglia contain multipolar neurons with several dendrites and a single axon that receive preganglionic cholinergic input. These neurons form synapses within the ganglion and project postganglionic fibers to effectors. Therefore the correct answer is d) Multipolar.
Q1. Preganglionic sympathetic fibers originate from which spinal segments?
a) Cervical only
b) Thoracolumbar (T1–L2)
c) Sacral only
d) Craniosacral
Explanation: Preganglionic sympathetic neurons arise from the intermediolateral cell column of the spinal cord segments T1–L2 (thoracolumbar outflow). These fibers synapse in paravertebral or prevertebral ganglia. Correct answer: b) Thoracolumbar (T1–L2).
Q2. Postganglionic sympathetic fibers predominantly release which neurotransmitter at effector organs?
a) Acetylcholine
b) Norepinephrine
c) Dopamine
d) GABA
Explanation: Most sympathetic postganglionic neurons release norepinephrine acting on α and β receptors at target organs. Exceptions include sweat glands (sympathetic cholinergic) and adrenal medulla (releases epinephrine/norepinephrine into blood). Correct answer: b) Norepinephrine.
Q3. Which ganglia form the sympathetic chain alongside the vertebral column?
a) Paravertebral ganglia
b) Prevertebral ganglia
c) Dorsal root ganglia
d) Cranial parasympathetic ganglia
Explanation: Paravertebral (sympathetic chain) ganglia lie bilaterally along the vertebral column and connect segmentally. They mediate sympathetic distribution to body wall and limbs. Prevertebral ganglia are anterior near abdominal vessels. Correct answer: a) Paravertebral ganglia.
Q4. The adrenal medulla acts like a sympathetic ganglion because its chromaffin cells:
a) Are derived from neural crest and release catecholamines into blood
b) Contain multipolar neurons with axons
c) Release acetylcholine at distant organs
d) Form synapses with skeletal muscle
Explanation: Adrenal medullary chromaffin cells are neural-crest-derived and respond to preganglionic cholinergic input by secreting epinephrine and norepinephrine into the circulation, functioning as endocrine equivalents of postganglionic sympathetic neurons. Correct answer: a).
Q5. Which of the following is a feature of sympathetic ganglia histology?
a) Presence of synaptic boutons between ganglionic neurons
b) Pseudounipolar neuronal soma
c) No satellite cells
d) Myelinated postganglionic fibers only
Explanation: Sympathetic ganglia display multipolar neuronal somata receiving preganglionic synapses; satellite cells are present. Postganglionic fibers are typically unmyelinated. The distinguishing feature is intraganglionic synapses; correct answer: a) Presence of synaptic boutons between ganglionic neurons.
Q6. A lesion of the sympathetic chain at T1 (Horner’s syndrome) causes which features ipsilaterally?
a) Ptosis, miosis, anhidrosis
b) Mydriasis and hyperhidrosis
c) Flaccid paralysis
d) Loss of taste
Explanation: Interruption of sympathetic outflow to the face produces Horner’s syndrome: ipsilateral ptosis (levator palpebrae dysfunction), miosis (unopposed parasympathetic), and anhidrosis. Correct answer: a) Ptosis, miosis, anhidrosis.
Q7. Which embryologic origin is shared by sympathetic ganglion neurons?
a) Neural tube
b) Neural crest
c) Endoderm
d) Mesoderm
Explanation: Sympathetic ganglion neurons originate from migrating neural crest cells that differentiate into peripheral neurons and glia. Neural tube gives rise to CNS structures. Correct answer: b) Neural crest.
Q8. Which receptor type predominates on vascular smooth muscle mediating sympathetic vasoconstriction?
a) β1-adrenergic
b) α1-adrenergic
c) Muscarinic M2
d) Nicotinic
Explanation: Sympathetic vasoconstriction is mediated mainly by norepinephrine acting on α1-adrenergic receptors on vascular smooth muscle, causing increased intracellular calcium and contraction. Correct answer: b) α1-adrenergic.
Q9. Which pharmacologic agent blocks transmission at autonomic ganglia (both sympathetic and parasympathetic)?
a) Atropine
b) Hexamethonium
c) Propranolol
d) Phenylephrine
Explanation: Ganglionic blockers like hexamethonium antagonize nicotinic receptors at autonomic ganglia, interrupting both sympathetic and parasympathetic transmission. Atropine blocks muscarinic receptors at effector sites. Correct answer: b) Hexamethonium.
Q10. Which statement about sympathetic postganglionic fibers is correct?
a) They are myelinated and fast conducting
b) They are unmyelinated and form varicosities over targets
c) They synapse onto skeletal muscle endplates
d) They release GABA at target organs
Explanation: Postganglionic sympathetic fibers are typically thin, unmyelinated C fibers that form en passant varicosities along target tissues, releasing neurotransmitter diffusely. They do not innervate skeletal muscle motor endplates. Correct answer: b).
Q11. Which clinical condition results from excessive sympathetic activity causing sustained vasoconstriction?
a) Orthostatic hypotension
b) Raynaud’s phenomenon
c) Myasthenia gravis
d) Guillain–Barré syndrome
Explanation: Raynaud’s phenomenon involves exaggerated sympathetic-mediated vasoconstriction of digital arterioles in response to cold or stress, causing pallor and ischemia. Orthostatic hypotension is due to inadequate sympathetic compensation. Correct answer: b) Raynaud’s phenomenon.
Chapter: Central Nervous System
Topic: Sensory Pathways
Subtopic: Dorsal Root Ganglion (DRG) Neurons
Keywords
- Dorsal root ganglion (DRG): Cluster of primary sensory neuron cell bodies in intervertebral foramina.
- Pseudounipolar neuron: Single process bifurcating into peripheral and central branches; soma is not in the conduction path.
- Satellite (capsular) cells: Glia enveloping DRG neuronal soma, providing metabolic support.
- Neural crest: Embryologic origin of DRG neurons and satellite cells/Schwann cells.
- Lipofuscin: Yellow-brown wear-and-tear pigment accumulating with age in long-lived neurons.
- Nissl substance: Rough endoplasmic reticulum in neuronal soma/dendrites; disperses during chromatolysis.
- T-junction: DRG axonal bifurcation reducing ectopic transmission; important in sensory signaling.
- Aδ and C fibers: Small-diameter nociceptive fibers with somata in DRG (sharp and dull pain).
- Herpes zoster: Varicella-zoster virus latency/reactivation in DRG causing dermatomal rash and pain.
- Autonomic ganglion: Multipolar neurons with synapses; contrasts with DRG which lacks intraganglionic synapses.
Lead Question – 2012
All the following features are seen in neurons from dorsal root ganglia, EXCEPT:
a) They are multipolar
b) They contain lipofuscin granules
c) They have centrally located nuclei
d) They are derived from neural crest cells
Explanation: DRG neurons are characteristically pseudounipolar (not multipolar), with large round soma, centrally located nuclei, prominent nucleoli, frequent lipofuscin, and neural crest origin. They lack synapses within the ganglion and are wrapped by satellite cells. Therefore, the false statement is a) They are multipolar.
Guessed Questions
1) The typical morphological type of a DRG neuron is:
a) Multipolar
b) Bipolar
c) Pseudounipolar
d) Pyramidal
Explanation: Primary sensory neurons in DRG are pseudounipolar with a single process that splits into peripheral and central branches at a T-junction. This design allows rapid transmission without synapsing on the soma. Correct answer: c) Pseudounipolar. Multipolar neurons are characteristic of autonomic ganglia and many CNS nuclei.
2) The glial cells that directly envelope DRG neuronal somata are:
a) Oligodendrocytes
b) Astrocytes
c) Satellite (capsular) cells
d) Microglia
Explanation: Satellite (capsular) cells form a continuous sheath around DRG neuronal soma, regulating the microenvironment and participating in pain modulation. Oligodendrocytes myelinate CNS axons, while Schwann cells (not listed) myelinate PNS axons. Correct answer: c) Satellite (capsular) cells.
3) A biopsy from a paraspinal ganglion shows large neurons with central nuclei, Nissl substance, lipofuscin, and no synapses between neurons. The structure is:
a) Sympathetic chain ganglion
b) Dorsal root ganglion
c) Ciliary ganglion
d) Enteric plexus
Explanation: Lack of intraganglionic synapses with centrally placed nuclei favors DRG. Autonomic ganglia (sympathetic/parasympathetic) contain multipolar neurons receiving synapses. DRG neurons are sensory and pseudounipolar. Correct answer: b) Dorsal root ganglion.
4) Embryologic origin of DRG neurons is:
a) Neural tube
b) Notochord
c) Neural crest
d) Mesoderm
Explanation: DRG neurons, Schwann cells, and satellite cells arise from neural crest, which migrates from the dorsal neural tube to form peripheral sensory ganglia. The neural tube forms CNS neurons and glia. Correct answer: c) Neural crest.
5) After transection of a peripheral branch of a DRG neuron, the soma shows chromatolysis. Which change is most typical?
a) Nuclear hyperchromasia and centralization
b) Nissl dispersal with eccentric nucleus and cell body swelling
c) Condensed Nissl with shrunken soma
d) Apoptotic bodies immediately
Explanation: Chromatolysis features dissolution of Nissl substance, cell body swelling, and eccentric displacement of the nucleus due to upregulated protein synthesis for axonal repair. Correct answer: b) Nissl dispersal with eccentric nucleus and cell body swelling.
6) Sharp, well-localized first pain from a pinprick is carried by fibers whose cell bodies lie in the DRG. These fibers are:
a) Aβ fibers
b) Aδ fibers
c) C fibers
d) Ia spindle afferents
Explanation: Aδ fibers are small, thinly myelinated afferents mediating fast, sharp pain and cold. Their somata reside in DRG. C fibers mediate slow, dull pain; Aβ carry touch/vibration; Ia are muscle spindle afferents. Correct answer: b) Aδ fibers.
7) A 65-year-old with dermatomal vesicular rash and burning pain over T6 likely has reactivation of varicella-zoster virus in the:
a) Ventral horn
b) Dorsal root ganglion
c) Sympathetic chain ganglion
d) Spinal cord dorsal column
Explanation: Herpes zoster lies dormant in DRG neurons and reactivates to cause dermatomal neuritis and rash. This localizes to the sensory ganglion at the affected level. Correct answer: b) Dorsal root ganglion.
8) Myelination of the peripheral process of a DRG neuron is performed by:
a) Oligodendrocytes
b) Schwann cells
c) Astrocytes
d) Microglia
Explanation: In the peripheral nervous system, Schwann cells myelinate individual axonal internodes, including the peripheral branch of DRG neurons. Oligodendrocytes myelinate CNS axons (multiple internodes). Correct answer: b) Schwann cells.
9) Functionally, the DRG neuron’s soma primarily:
a) Actively conducts action potentials
b) Serves trophic and metabolic roles while the impulse bypasses the soma
c) Generates synaptic potentials with neighboring DRG neurons
d) Integrates dendritic inputs from spinal interneurons
Explanation: In pseudounipolar neurons, the action potential travels from peripheral to central process across a T-junction, largely bypassing the soma. The soma provides metabolic support; DRG lacks interneuronal synapses. Correct answer: b) Serves trophic and metabolic roles….
10) Which feature best distinguishes a sympathetic ganglion from a DRG histologically?
a) Presence of satellite cells
b) Multipolar neurons receiving synapses within the ganglion
c) Central nuclei in neurons
d) Lipofuscin granules
Explanation: Autonomic (sympathetic) ganglia contain multipolar neurons receiving preganglionic synapses; DRG neurons are pseudounipolar with no intraganglionic synapses. Both have satellite cells and may show lipofuscin. Nuclei are often eccentric in autonomic ganglia. Correct answer: b) Multipolar neurons receiving synapses within the ganglion.
11) A patient with radicular pain from L5 nerve root compression has primary sensory neuron cell bodies located in the:
a) Dorsal horn lamina II
b) Dorsal root ganglion at L5
c) Ventral root
d) Sympathetic chain at L5
Explanation: Primary sensory neuron somata reside in the DRG at the corresponding spinal level (here, L5). Their central processes enter the dorsal root to synapse in dorsal horn or ascend in dorsal columns. Correct answer: b) Dorsal root ganglion at L5.
Chapter: Central Nervous System | Topic: Motor System | Subtopic: Motor Planning & Postural Set
Keywords
Supplementary motor area (SMA) — medial frontal region involved in planning, initiating complex and bimanual movements and setting postural tone.
Premotor cortex — lateral frontal area organizing movements in response to external cues and sensory guidance.
Primary motor cortex (M1) — executes voluntary movements; somatotopically organized.
Postural set — anticipatory adjustment of posture before voluntary movement to maintain balance.
Motor planning — preparation and sequencing of movement components prior to execution.
Apraxia — impairment of learned purposeful movements despite intact strength and comprehension.
Basal ganglia — selection/gating of motor programs and modulation of movement initiation.
Cerebellum — timing, coordination, and adaptive control of movements and posture.
Feedforward control — anticipatory motor adjustments based on predicted outcomes.
Pharmacologic/lesion effects — focal lesions produce specific deficits in planning or execution.
Lead Question - 2012
Setting posture before planned movement ?
a) Premotor cortex
b) Motor cortex
c) Frontal
d) Supplementary motor cortex
Explanation: The supplementary motor area (SMA) is primarily responsible for internally generated movement planning and anticipatory postural adjustments (postural set) before voluntary actions, especially for bimanual and sequential tasks. Lesions cause impaired initiation and postural preparation. Correct answer: d) Supplementary motor cortex.
Q2. A patient cannot initiate a self-paced sequence of movements but moves normally to external cues. Which area is likely affected?
a) Primary motor cortex
b) Premotor cortex
c) Supplementary motor area
d) Somatosensory cortex
Explanation: SMA lesions impair internally generated, self-initiated sequences while externally cued movements remain relatively preserved due to premotor circuits. Patients show akinesia or difficulty initiating learned sequences. Correct answer: c) Supplementary motor area. Rehabilitation uses external cues to bypass SMA deficits.
Q3. Which structure provides timing and coordination for anticipatory postural adjustments?
a) Cerebellum
b) Broca’s area
c) Hippocampus
d) Occipital lobe
Explanation: The cerebellum refines timing and coordination of both movement execution and anticipatory postural adjustments by integrating sensory inputs and motor plans. Cerebellar lesions produce dysmetria and impaired postural control. Correct answer: a) Cerebellum. It works with SMA for smooth movement onset.
Q4. A lesion in the lateral premotor cortex most likely impairs:
a) Internally-generated bimanual sequencing
b) Response to external sensory cues
c) Primary muscle strength
d) Long-term memory
Explanation: The lateral premotor area is important for selecting and preparing movements guided by external sensory cues. Lesions reduce cue-driven responses and impair reaching based on visual instructions. Correct answer: b) Response to external sensory cues; strength (M1) and memory are not primarily affected.
Q5. Which clinical sign suggests SMA dysfunction?
a) Contralateral spastic weakness only
b) Difficulty performing learned sequences without cues
c) Pure sensory loss
d) Visual field defect
Explanation: SMA damage causes difficulty initiating learned motor sequences and impaired bimanual coordination; actions may be performed with external prompting. While M1 lesions cause weakness, SMA lesions mainly affect initiation and sequencing. Correct answer: b). Assess by asking patient to perform self-initiated tasks.
Q6. Deep brain structures that gate motor programs and influence postural set include:
a) Basal ganglia
b) Optic chiasm
c) Medulla oblongata only
d) Corpus callosum
Explanation: Basal ganglia circuits select and facilitate appropriate motor programs and modulate posture and initiation. Dysfunction causes bradykinesia, rigidity, and impaired preparatory postural adjustments. Correct answer: a) Basal ganglia. They interact with SMA and premotor areas for smooth motor control.
Q7. Which test assesses anticipatory postural adjustments related to SMA function?
a) Ask patient to raise one arm quickly while observing weight shift
b) Visual acuity chart
c) Pure tone audiometry
d) Deep tendon reflex testing
Explanation: Observing compensatory weight shift when a patient rapidly raises an arm evaluates anticipatory postural adjustments. SMA dysfunction yields inadequate preparatory shifts and imbalance. Correct answer: a). This bedside test reveals impaired feedforward control of posture.
Q8. A patient with SMA lesion may exhibit which of the following during bimanual tasks?
a) Improved coordination
b) Apraxia for learned bimanual sequences
c) Enhanced reflexes only
d) Loss of primary sensation
Explanation: SMA lesions impair planning and coordination of bimanual and sequential movements, causing apraxia for learned tasks. Reflexes and primary sensation are not the primary deficits. Correct answer: b). Rehabilitation focuses on externally cued retraining to bypass SMA.
Q9. Which neurotransmitter system in basal ganglia influences movement initiation that complements SMA function?
a) Dopaminergic
b) Cholinergic only
c) GABAergic only
d) Serotonergic only
Explanation: Dopaminergic input from the substantia nigra modulates basal ganglia output and facilitates movement initiation, interacting with SMA planning. Dopamine deficiency (Parkinson’s) causes impaired initiation and reduced anticipatory postural adjustments. Correct answer: a) Dopaminergic.
Q10. Lesion affecting the supplementary motor area bilaterally may cause:
a) Difficulty initiating voluntary movements (akinetic mutism)
b) Pure sensory loss
c) Hyperreflexia only
d) Visual agnosia
Explanation: Bilateral SMA damage can cause severe akinesia and reduced spontaneous movement, sometimes akinetic mutism, and impaired postural preparation. Sensory and visual functions are spared. Correct answer: a). Management may include dopaminergic and rehabilitative strategies.
Q11. Which cortical area is mainly responsible for execution of a precise voluntary finger movement?
a) Primary motor cortex (M1)
b) Supplementary motor area
c) Occipital cortex
d) Broca’s area
Explanation: Primary motor cortex (M1) contains the final corticospinal output neurons that execute fine, precise voluntary movements such as individual finger actions. SMA plans and primes posture; M1 performs the actual contraction. Correct answer: a) Primary motor cortex (M1).
Chapter: Central Nervous System | Topic: Somatosensory System | Subtopic: Cortical Sensory Functions
Keywords
Primary somatosensory cortex — postcentral gyrus; processes discriminative touch and proprioception.
Stereognosis — recognition of objects by touch; cortical function.
Two-point discrimination — spatial acuity mediated by S1.
Graphesthesia — recognizing writing on skin; cortical sensory test.
Astereognosis — inability to identify objects by touch; indicates cortical lesion.
Thalamus — relay station for somatic sensory pathways to cortex.
Spinothalamic tract — transmits pain and temperature to thalamus/cortex.
Proprioception — limb position sense; dorsal columns and cortex.
Neglect — parietal lobe dysfunction causing inattention to one side.
Localization — identifying site of tactile stimulus; a cortical discriminative ability.
Lead Question - 2012
Somatosensory cortex lesion will cause ?
a) Pain
b) Temperature
c) Localization
d) Vibration
Explanation: The primary somatosensory cortex is essential for discriminative touch tasks such as localization, two-point discrimination, stereognosis and graphesthesia. A cortical lesion impairs the ability to localize stimuli despite preserved basic pain and temperature sensation. Correct answer is c) Localization.
Q2. A patient cannot identify an object by touch but can feel it; this sign is called:
a) Anosmia
b) Astereognosis
c) Hemianopia
d) Agraphia
Explanation: Astereognosis is the inability to recognize objects by touch despite intact primary sensation, indicating contralateral parietal or postcentral gyrus dysfunction. It reflects impaired cortical processing of tactile information. Correct answer: b) Astereognosis. This helps localize lesions to somatosensory cortex.
Q3. Loss of two-point discrimination on the right hand suggests lesion in:
a) Left primary somatosensory cortex
b) Right dorsal column
c) Left cerebellum
d) Peripheral nerve only
Explanation: Two-point discrimination is a cortical function processed in the contralateral primary somatosensory cortex. Loss on the right hand indicates a lesion in the left postcentral gyrus. Peripheral lesions can reduce sensation but cortical loss specifically impairs spatial discrimination. Correct answer: a).
Q4. In a pure postcentral gyrus infarct, which sensation is most likely preserved?
a) Stereognosis
b) Pain perception
c) Two-point discrimination
d) Graphesthesia
Explanation: Basic pain perception often remains because spinothalamic pathways reach thalamus and brainstem centers; however discriminative tasks (stereognosis, two-point discrimination, graphesthesia) require cortical processing and are impaired. Thus pain perception may be relatively preserved; correct answer: b).
Q5. A lesion of the secondary somatosensory cortex most affects:
a) Conscious pain detection
b) Integration and recognition of complex tactile patterns
c) Spinal reflexes
d) Muscle tone
Explanation: Secondary somatosensory cortex integrates tactile information for higher functions like texture discrimination and object recognition. Lesions impair complex tactile perception but not basic detection. Correct answer: b). Clinical tests include stereognosis and graphesthesia to detect such deficits.
Q6. Hemineglect (inattention to one side) most commonly results from lesion in:
a) Dominant parietal lobe
b) Nondominant parietal lobe
c) Occipital lobe
d) Brainstem
Explanation: Hemineglect is typically due to damage of the nondominant (usually right) parietal cortex, causing inattention to the contralateral side. It affects awareness more than primary sensation. Correct answer: b). This is tested by cancellation tasks and sensory stimulation.
Q7. Graphesthesia testing assesses which function?
a) Pain localization
b) Ability to recognize writing on skin
c) Vibration sense
d) Proprioception
Explanation: Graphesthesia is recognizing letters or numbers traced on the skin and depends on intact cortical sensory areas. Loss suggests parietal lobe dysfunction. Correct answer: b). It complements stereognosis and two-point discrimination in cortical assessment.
Q8. A thalamic stroke most commonly causes which sensory deficit?
a) Pure motor weakness only
b) Contralateral hemisensory loss including pain and temperature
c) Ipsilateral loss of vibration only
d) Loss of smell
Explanation: The thalamus relays most somatic sensory modalities to cortex; a thalamic stroke causes contralateral hemisensory loss affecting pain, temperature, touch and proprioception. Correct answer: b). Thalamic pain syndrome can follow with chronic dysesthesia.
Q9. Dissociation of pain and touch (lost pain but preserved touch) indicates lesion in:
a) Dorsal columns
b) Spinothalamic tract
c) Peripheral nerves only
d) Primary motor cortex
Explanation: Loss of pain and temperature with preserved dorsal column modalities suggests spinal cord lesion affecting the spinothalamic tract (e.g., syringomyelia). Correct answer: b). Cortical lesions typically affect discriminative touch rather than abolish pain selectively.
Q10. A patient with cortical sensory loss will most likely fail which bedside test?
a) Reflex hammer tendon reflex
b) Two-point discrimination
c) Muscle strength testing
d) Pupillary light reflex
Explanation: Two-point discrimination depends on cortical sensory processing; cortical lesions impair this test. Tendon reflexes and muscle strength reflect spinal and motor pathways. Pupillary reflex is brainstem mediated. Correct answer: b). This helps distinguish cortical from peripheral sensory loss.
Q11. Which sign suggests parietal lobe (cortical) sensory dysfunction rather than peripheral neuropathy?
a) Stocking-glove numbness
b) Astereognosis
c) Diminished ankle reflex
d) Burning pain in feet
Explanation: Astereognosis (inability to recognize objects by touch) indicates cortical parietal dysfunction. Peripheral neuropathies produce distal symmetric sensory loss and reflex changes. Correct answer: b). Identifying astereognosis localizes lesion to somatosensory cortex.
Chapter: Central Nervous System
Topic: Basal Ganglia
Subtopic: Striatum and Memory Functions
Keywords
- Striatum: Part of basal ganglia involved in motor control and habit learning.
- Procedural memory: Memory for skills and habits, dependent on basal ganglia.
- Explicit memory: Conscious recall of facts and events, mediated by hippocampus.
- Short-term memory: Temporary information storage lasting seconds to minutes.
- Long-term memory: Stable memory stored for days to years.
- Parkinsonism: Clinical syndrome due to basal ganglia dysfunction.
Lead Question – 2012
Striatum damage affects primarily?
a) Procedural memory
b) Short term memory
c) Long term memory
d) Explicit memory
Explanation: The striatum, part of the basal ganglia, regulates procedural memory linked to skills and habits. Unlike hippocampus-driven explicit memory, striatal injury impairs motor learning such as riding a bicycle or typing, while short- and long-term declarative memories remain intact. Correct answer: (a) Procedural memory.
Guessed Questions
1) A Parkinson’s patient struggles with buttoning his shirt. Which memory type is impaired?
a) Procedural memory
b) Explicit memory
c) Short term memory
d) Episodic memory
Explanation: Parkinson’s disease impairs basal ganglia circuits, particularly the striatum, which controls learned motor skills. Patients lose smooth execution of habitual actions. Declarative and episodic recall remain intact. Correct answer: (a) Procedural memory.
2) A stroke involving the hippocampus mainly affects:
a) Habit learning
b) Procedural skills
c) Explicit memory
d) Reflex conditioning
Explanation: The hippocampus is essential for consolidation of declarative memories, including facts and events. Stroke injury here produces severe anterograde amnesia for explicit memory, but motor habits and reflex learning remain intact. Correct answer: (c) Explicit memory.
3) Which memory remains unaffected in striatal lesions?
a) Motor habits
b) Procedural skills
c) Explicit memory
d) Skill learning
Explanation: Striatal lesions disrupt motor habits and procedural learning. Explicit memory, mediated by hippocampus and temporal cortex, stays preserved in such patients. They can recall events but struggle with habit execution. Correct answer: (c) Explicit memory.
4) A patient can recall his wedding day but cannot play the piano anymore after basal ganglia injury. This reflects loss of:
a) Explicit memory
b) Procedural memory
c) Short term memory
d) Semantic memory
Explanation: Piano playing is a learned skill relying on procedural memory, dependent on striatal circuits. Episodic recall, like remembering wedding details, involves hippocampus and remains unaffected. Correct answer: (b) Procedural memory.
5) In Huntington’s disease, degeneration of the striatum causes early:
a) Loss of semantic memory
b) Loss of episodic recall
c) Impaired procedural memory
d) Impaired short-term storage
Explanation: Huntington’s disease selectively damages the caudate and putamen (striatum). Patients show impaired motor learning and skill execution due to loss of procedural memory, while semantic and episodic memory are relatively intact early. Correct answer: (c) Impaired procedural memory.
6) Procedural memory is best tested by:
a) Word recall
b) Mirror tracing task
c) Object naming
d) Sentence repetition
Explanation: Procedural memory is assessed through tasks requiring skill learning, such as mirror tracing or rotary pursuit. Word recall and object naming depend on explicit memory and language centers. Correct answer: (b) Mirror tracing task.
7) A patient retains ability to solve arithmetic problems but forgets new motor skills after basal ganglia injury. Which is intact?
a) Procedural memory
b) Habit learning
c) Explicit memory
d) Reflex motor learning
Explanation: Arithmetic skills and fact-based knowledge depend on explicit memory stored in the cortex and hippocampus. These remain intact despite striatal injury. Procedural learning is impaired. Correct answer: (c) Explicit memory.
8) Which brain structure primarily encodes explicit long-term memory?
a) Striatum
b) Hippocampus
c) Amygdala
d) Cerebellum
Explanation: The hippocampus consolidates explicit long-term memory such as facts and events. The striatum mediates procedural memory, the amygdala processes emotional memory, and the cerebellum handles motor coordination. Correct answer: (b) Hippocampus.
9) Striatal injury spares which of the following?
a) Habit learning
b) Skill acquisition
c) Declarative recall
d) Motor sequence learning
Explanation: Declarative recall (explicit memory) is dependent on hippocampal circuits and not the striatum. Therefore, patients with striatal lesions can still recall facts but fail to perform acquired habits. Correct answer: (c) Declarative recall.
10) A medical student learns to perform venipuncture. Which memory system is reinforced?
a) Procedural memory
b) Short term memory
c) Semantic memory
d) Episodic memory
Explanation: Skill-based learning such as venipuncture is stored in procedural memory, relying on striatal and cerebellar circuits. Over time, repetition strengthens habit execution independent of conscious recall. Correct answer: (a) Procedural memory.
11) A patient with amnesia can still play the guitar skillfully. Which memory is preserved?
a) Explicit memory
b) Procedural memory
c) Episodic memory
d) Semantic memory
Explanation: Amnesia typically impairs explicit (declarative) memory while sparing procedural memory. Thus, the patient cannot recall past events but continues to perform learned motor skills such as guitar playing. Correct answer: (b) Procedural memory.
Chapter: Neuroanatomy
Topic: Cerebellum
Subtopic: Cerebellar Cortex
Keywords:
Cerebellar cortex: Three-layered structure of cerebellum responsible for motor coordination.
Molecular layer: Outer layer containing stellate and basket cells.
Purkinje cells: Principal output neurons of cerebellar cortex.
Granule cells: Smallest excitatory neurons forming parallel fibers.
Golgi cells: Inhibitory interneurons regulating granule cell activity.
Clinical relevance: Damage to cerebellar cortex causes ataxia, tremor, and dysmetria.
Lead Question - 2012
What are the cellular contents of cerebellar cortex?
a) Cortical cells
b) Glomus cells
c) Principle cells
d) Intercalated cells
Explanation: The cerebellar cortex has three layers containing five neuron types: Purkinje cells, granule cells, basket cells, stellate cells, and Golgi cells. Purkinje cells are the principal output neurons. Correct answer is Principle cells referring to Purkinje cells, essential for inhibitory output to deep cerebellar nuclei.
Guessed Question 1
Which is the only excitatory neuron of the cerebellar cortex?
a) Purkinje cells
b) Granule cells
c) Basket cells
d) Golgi cells
Explanation: Among cerebellar neurons, granule cells are the only excitatory type, releasing glutamate. Purkinje, basket, stellate, and Golgi cells are inhibitory GABAergic neurons. Correct answer is Granule cells.
Guessed Question 2
Purkinje cells exert their effect through:
a) Excitatory input to thalamus
b) Inhibitory output to deep cerebellar nuclei
c) Excitatory connections with cortex
d) Inhibitory effect on spinal cord
Explanation: Purkinje cells are GABAergic and provide the sole output from the cerebellar cortex, inhibiting deep cerebellar nuclei. This helps fine-tune motor control. Correct answer is Inhibitory output to deep cerebellar nuclei.
Guessed Question 3
Which cells in molecular layer form synapses on Purkinje cell dendrites?
a) Basket and stellate cells
b) Granule cells
c) Golgi cells
d) Glial cells
Explanation: The molecular layer contains basket and stellate cells which are inhibitory interneurons. They synapse on Purkinje cell dendrites and modulate their activity. Correct answer is Basket and stellate cells.
Guessed Question 4
Which neurotransmitter is released by Purkinje cells?
a) Glutamate
b) GABA
c) Dopamine
d) Glycine
Explanation: Purkinje cells are large inhibitory neurons of cerebellum releasing GABA. This inhibition regulates output from deep cerebellar nuclei and maintains motor coordination. Correct answer is GABA.
Guessed Question 5
Damage to Purkinje cells results in:
a) Ataxia
b) Rigidity
c) Hemiballismus
d) Tremor at rest
Explanation: Purkinje cell loss impairs inhibitory regulation, causing cerebellar ataxia with uncoordinated gait, intention tremor, and dysmetria. Unlike Parkinsonism, rigidity and resting tremor are absent. Correct answer is Ataxia.
Guessed Question 6
Which layer of cerebellar cortex contains Purkinje cell bodies?
a) Molecular layer
b) Purkinje cell layer
c) Granular layer
d) White matter
Explanation: Purkinje cells lie in a single row between the molecular and granular layers, forming the Purkinje cell layer. Their dendrites extend into molecular layer. Correct answer is Purkinje cell layer.
Guessed Question 7
Golgi cells provide inhibitory input to:
a) Purkinje cells
b) Basket cells
c) Granule cells
d) Stellate cells
Explanation: Golgi cells are inhibitory interneurons located in the granular layer. They regulate granule cell activity through inhibitory synapses, modulating parallel fiber output. Correct answer is Granule cells.
Guessed Question 8
Which afferent fibers excite Purkinje cells via climbing fibers?
a) Mossy fibers
b) Corticospinal fibers
c) Vestibulospinal fibers
d) Olivocerebellar fibers
Explanation: Climbing fibers arise from inferior olivary nucleus and directly synapse on Purkinje cell dendrites with strong excitatory input. Mossy fibers excite granule cells instead. Correct answer is Olivocerebellar fibers.
Guessed Question 9
Mossy fibers primarily synapse with:
a) Purkinje cells
b) Granule cells
c) Golgi cells
d) Stellate cells
Explanation: Mossy fibers form excitatory synapses with granule cells in the cerebellar granular layer. These granule cells then send parallel fibers to excite Purkinje cells indirectly. Correct answer is Granule cells.
Guessed Question 10
Clinical feature of midline cerebellar lesion (vermis) is:
a) Truncal ataxia
b) Intention tremor
c) Hemiballismus
d) Resting tremor
Explanation: Lesions in vermis affect axial muscles leading to truncal ataxia, wide-based gait, and imbalance. Intention tremor is seen in hemispheric lesions. Correct answer is Truncal ataxia.
Chapter: Neuroanatomy
Topic: Cerebral Hemispheres
Subtopic: Corpus Callosum
Keywords:
Corpus callosum: Largest commissural fiber tract connecting right and left cerebral hemispheres.
Hemispheric connection: Corpus callosum unites the two hemispheres for integration.
Frontal lobe connection: Anterior part (genu) connects the two frontal lobes.
Commissural fibers: White matter tracts connecting similar cortical areas of both hemispheres.
Split-brain syndrome: Condition after corpus callosotomy leading to loss of hemispheric integration.
Lead Question - 2012
True about Corpus callosum :
a) Unite far area of two sides of brain
b) Connect two frontal lobe
c) Unite two hemisphere
d) All
Explanation: Corpus callosum is the major commissural bundle uniting the two hemispheres. It connects frontal lobes (via genu), parietal lobes (body), and occipital lobes (splenium). It enables interhemispheric communication. Hence, all the given statements are true, making the correct answer All.
Guessed Question 1
A lesion in the corpus callosum can lead to:
a) Split-brain syndrome
b) Horner’s syndrome
c) Parkinsonism
d) Hemiballismus
Explanation: Lesions in corpus callosum disrupt interhemispheric communication leading to split-brain syndrome. Patients may fail to name objects in the left visual field due to disconnection between hemispheres. Correct answer is Split-brain syndrome.
Guessed Question 2
Anterior part of corpus callosum (genu) primarily connects:
a) Occipital lobes
b) Frontal lobes
c) Temporal lobes
d) Thalamus
Explanation: The genu of corpus callosum bends forward and connects the two frontal lobes, enabling coordinated executive and motor function across hemispheres. Correct answer is Frontal lobes.
Guessed Question 3
The splenium of the corpus callosum connects:
a) Frontal lobes
b) Parietal lobes
c) Occipital lobes
d) Temporal lobes
Explanation: The posterior part of corpus callosum is the splenium, which connects occipital lobes and allows integration of visual information between hemispheres. Correct answer is Occipital lobes.
Guessed Question 4
Which imaging modality best visualizes corpus callosum abnormalities?
a) CT scan
b) MRI
c) Ultrasound
d) PET scan
Explanation: MRI is the most sensitive imaging modality for detecting corpus callosum malformations, agenesis, or demyelination. It clearly shows its structure and fiber connections. Correct answer is MRI.
Guessed Question 5
Congenital absence of corpus callosum is associated with:
a) Agenesis syndromes
b) Huntington’s disease
c) Amyotrophic lateral sclerosis
d) Multiple sclerosis
Explanation: Agenesis of corpus callosum is a congenital malformation, often linked with developmental delay, seizures, and midline anomalies. Correct answer is Agenesis syndromes.
Guessed Question 6
Which part of corpus callosum connects parietal lobes?
a) Genu
b) Body
c) Splenium
d) Rostrum
Explanation: The central part or body of corpus callosum mainly connects parietal lobes, allowing somatosensory integration across hemispheres. Correct answer is Body.
Guessed Question 7
Damage to corpus callosum may impair:
a) Interhemispheric communication
b) Reflex arcs
c) Spinal cord conduction
d) Basal ganglia circuits
Explanation: Corpus callosum is essential for communication between hemispheres. Its damage leads to disconnection syndromes, affecting coordinated tasks involving both sides of the body. Correct answer is Interhemispheric communication.
Guessed Question 8
Which condition is treated by partial corpus callosotomy?
a) Intractable epilepsy
b) Multiple sclerosis
c) Meningitis
d) Brain abscess
Explanation: In refractory epilepsy, partial callosotomy prevents seizure spread between hemispheres, reducing drop attacks. Correct answer is Intractable epilepsy.
Guessed Question 9
Which fibers are carried by corpus callosum?
a) Commissural fibers
b) Association fibers
c) Projection fibers
d) Reticular fibers
Explanation: Corpus callosum carries commissural fibers connecting identical cortical areas of both hemispheres. Association fibers connect areas within the same hemisphere, while projection fibers connect cortex with lower centers. Correct answer is Commissural fibers.
Guessed Question 10
In MRI, corpus callosum appears as:
a) Hypointense on T1, Hyperintense on T2
b) Hyperintense on T1, Hypointense on T2
c) Isointense on both T1 and T2
d) Variable with pathology
Explanation: On MRI, corpus callosum is typically hypointense on T1 and hyperintense on T2 due to its myelinated white matter. Signal changes vary with demyelination or agenesis. Correct answer is Hypointense on T1, Hyperintense on T2.
Chapter: Neuroanatomy
Topic: Cranial Nerves
Subtopic: Oculomotor Nerve (III)
Keywords:
Oculomotor nerve: The third cranial nerve, motor to most extraocular muscles.
Parasympathetic fibers: Carried to ciliary ganglion for pupil constriction.
Inferior oblique muscle: Supplied by oculomotor nerve, elevates eye in adduction.
Superior orbital fissure: Route by which oculomotor enters orbit.
Pupil constriction: Mediated by sphincter pupillae via oculomotor parasympathetic supply.
Lead Question - 2012
All the following are characteristics of oculomotor nerve except:
a) Carries parasympathetic nerve fibres
b) Supplies inferior oblique muscle
c) Enters orbit through the inferior orbital fissure
d) Causes constriction of pupil
Explanation: The oculomotor nerve enters the orbit through the superior orbital fissure, not the inferior orbital fissure. It supplies extraocular muscles and parasympathetics to sphincter pupillae, causing pupillary constriction. Thus, the incorrect statement is Enters orbit through the inferior orbital fissure.
Guessed Question 1
A lesion of the oculomotor nerve results in:
a) Ptosis, mydriasis, eye down and out
b) Loss of corneal reflex
c) Diplopia only in horizontal gaze
d) Isolated nystagmus
Explanation: Oculomotor palsy produces ptosis (levator palpebrae), mydriasis (parasympathetics), and eye deviation down and out (unopposed lateral rectus and superior oblique). Correct answer is Ptosis, mydriasis, eye down and out.
Guessed Question 2
Parasympathetic fibers of oculomotor nerve synapse in:
a) Ciliary ganglion
b) Pterygopalatine ganglion
c) Otic ganglion
d) Submandibular ganglion
Explanation: The oculomotor nerve carries preganglionic parasympathetics that synapse in the ciliary ganglion, from where short ciliary nerves innervate sphincter pupillae and ciliary muscle. Correct answer is Ciliary ganglion.
Guessed Question 3
A patient with diabetes develops acute third nerve palsy but pupil is spared. This suggests:
a) Compressive lesion
b) Ischemic neuropathy
c) Tumor invasion
d) Inflammatory neuritis
Explanation: In ischemic oculomotor palsy (like in diabetes), central fibers are affected while peripheral parasympathetic fibers are spared, preserving pupillary function. Compressive lesions usually affect the pupil. Correct answer is Ischemic neuropathy.
Guessed Question 4
Which extraocular muscle is NOT supplied by oculomotor nerve?
a) Superior rectus
b) Inferior rectus
c) Superior oblique
d) Inferior oblique
Explanation: Oculomotor supplies all extraocular muscles except lateral rectus (abducens) and superior oblique (trochlear). Thus, correct answer is Superior oblique.
Guessed Question 5
The nucleus of oculomotor nerve is located in:
a) Midbrain at superior colliculus level
b) Midbrain at inferior colliculus level
c) Pons
d) Medulla
Explanation: The oculomotor nucleus is located in the midbrain at the level of the superior colliculus, ventral to the aqueduct. Correct answer is Midbrain at superior colliculus level.
Guessed Question 6
A compressive aneurysm of posterior communicating artery typically causes:
a) Pupil-involving oculomotor palsy
b) Pupil-sparing oculomotor palsy
c) Isolated superior oblique weakness
d) Bilateral ptosis without diplopia
Explanation: Aneurysms compress the superficial parasympathetic fibers of oculomotor nerve, leading to early pupillary involvement along with third nerve palsy. Correct answer is Pupil-involving oculomotor palsy.
Guessed Question 7
Which clinical sign is most specific for oculomotor nerve palsy?
a) Ptosis
b) Miosis
c) Lateral gaze palsy
d) Nystagmus
Explanation: Ptosis caused by paralysis of levator palpebrae superioris is a hallmark feature of oculomotor nerve palsy, often seen with diplopia and pupil dilation. Correct answer is Ptosis.
Guessed Question 8
The Edinger–Westphal nucleus provides fibers for:
a) Accommodation and pupillary constriction
b) Extraocular muscle contraction
c) Taste perception
d) Facial sensation
Explanation: The Edinger–Westphal nucleus, part of oculomotor complex, gives parasympathetic fibers that control accommodation reflex and pupillary constriction via ciliary ganglion. Correct answer is Accommodation and pupillary constriction.
Guessed Question 9
A patient presents with eye deviated down and out with dilated pupil. The most likely cause is:
a) Oculomotor nerve palsy
b) Trochlear nerve palsy
c) Abducens nerve palsy
d) Optic nerve lesion
Explanation: Down-and-out eye with dilated pupil indicates oculomotor palsy as lateral rectus and superior oblique act unopposed. Correct answer is Oculomotor nerve palsy.
Guessed Question 10
Which clinical test best assesses oculomotor function?
a) Ask patient to look laterally
b) Check convergence and accommodation
c) Assess corneal reflex
d) Test jaw movement
Explanation: Convergence and accommodation require action of medial rectus and ciliary muscle, both supplied by oculomotor nerve. Hence, testing accommodation is an effective way to assess its function. Correct answer is Check convergence and accommodation.
Chapter: Neuroanatomy
Topic: Cerebral Cortex
Subtopic: Sulci and Gyri
Keywords:
Operculated sulcus: A sulcus covered partially by cortical opercula (frontal, parietal, temporal lobes).
Calcarine sulcus: Found in occipital lobe, related to primary visual cortex.
Collateral sulcus: Separates fusiform gyrus from parahippocampal gyrus.
Lunate sulcus: Seen in some primates, rare in humans.
Central sulcus: Separates frontal and parietal lobes.
Lead Question - 2012
Which of the following is an operculated sulcus ?
a) Calcarine
b) Collateral
c) Lunate
d) Central
Explanation: The central sulcus is an operculated sulcus, as parts of the frontal, parietal, and temporal lobes form opercula around the insula. Operculation is a covering phenomenon seen around the insula. Hence, the correct answer is Central sulcus.
Guessed Question 1
A lesion of the calcarine sulcus results in loss of:
a) Auditory perception
b) Visual field
c) Language comprehension
d) Motor function
Explanation: The calcarine sulcus contains the primary visual cortex (Brodmann area 17). A lesion leads to contralateral homonymous hemianopia. Thus, the answer is Visual field.
Guessed Question 2
The collateral sulcus is located in:
a) Occipital lobe
b) Temporal lobe
c) Parietal lobe
d) Frontal lobe
Explanation: The collateral sulcus is found in the temporal lobe, separating fusiform gyrus from parahippocampal gyrus. It plays a role in higher-order visual processing. Answer is Temporal lobe.
Guessed Question 3
Which sulcus separates motor and sensory cortices?
a) Calcarine
b) Central
c) Lunate
d) Collateral
Explanation: The central sulcus separates the precentral gyrus (motor cortex) from the postcentral gyrus (sensory cortex). This functional division is crucial in neurosurgery. Answer is Central sulcus.
Guessed Question 4
Lunate sulcus is considered a remnant of evolution, more prominent in:
a) Humans
b) Primates
c) Amphibians
d) Birds
Explanation: The lunate sulcus is more prominent in primates like apes and monkeys, rarely observed in humans. It demarcates visual areas in non-human primates. Answer is Primates.
Guessed Question 5
The insula is hidden deep to which sulcus?
a) Central
b) Lateral
c) Calcarine
d) Collateral
Explanation: The insula is buried deep within the lateral sulcus, covered by opercula of adjacent lobes. It is involved in autonomic and visceral functions. Answer is Lateral sulcus.
Guessed Question 6
Which artery supplies the region around the central sulcus?
a) Middle cerebral artery
b) Anterior cerebral artery
c) Posterior cerebral artery
d) Basilar artery
Explanation: The central sulcus is supplied by both anterior and middle cerebral arteries. The anterior cerebral supplies medial aspect, and MCA supplies lateral aspect. Answer is Anterior cerebral artery.
Guessed Question 7
A stroke involving the calcarine sulcus territory typically spares:
a) Central vision
b) Peripheral vision
c) Entire vision
d) Color vision
Explanation: A stroke involving posterior cerebral artery affecting calcarine cortex causes contralateral homonymous hemianopia with macular sparing, as macular area has dual supply. Answer is Central vision.
Guessed Question 8
The collateral sulcus is most closely associated with:
a) Olfactory processing
b) Visual memory
c) Auditory signals
d) Motor control
Explanation: The collateral sulcus is related to the fusiform and parahippocampal gyri, involved in recognition and visual memory processes. Answer is Visual memory.
Guessed Question 9
The central sulcus is also called:
a) Fissure of Rolando
b) Fissure of Sylvius
c) Fissure of Broca
d) Fissure of Wernicke
Explanation: The central sulcus is known as the fissure of Rolando, a landmark separating frontal and parietal lobes. Answer is Fissure of Rolando.
Guessed Question 10
Which sulcus lies in the occipital lobe and is crucial for vision?
a) Central
b) Calcarine
c) Collateral
d) Sylvian
Explanation: The calcarine sulcus in the occipital lobe contains the primary visual cortex. It is essential for processing vision. Answer is Calcarine sulcus.
Chapter: Neuroanatomy
Topic: Dorsal Column Nuclei & Medial Lemniscus Pathway
Subtopic: Nucleus Gracilis/Cuneatus (aka “fasciculate” nuclei), Sensory Decussation & Clinical Correlates
Keyword Definitions
Fasciculus gracilis — Medial dorsal column carrying fine touch, vibration, proprioception from lower limb/trunk.
Fasciculus cuneatus — Lateral dorsal column carrying similar modalities from upper limb/upper trunk.
Nucleus gracilis — Relay nucleus in caudal medulla for fasciculus gracilis; gives internal arcuate fibers.
Nucleus cuneatus — Relay nucleus in caudal medulla for fasciculus cuneatus; projects to medial lemniscus.
Internal arcuate fibers — Axons from dorsal column nuclei that decussate in caudal medulla (sensory decussation).
Medial lemniscus — Ascending tract after decussation to VPL thalamus conveying touch, vibration, proprioception.
Accessory cuneate nucleus — Lateral to cuneate; origin of cuneocerebellar tract (ipsilateral proprioception to cerebellum).
Proprioception — Sense of joint position/movement; tested by joint position sense, Romberg.
Romberg test — Instability with eyes closed suggests proprioceptive deficit (e.g., dorsal column disease).
Tabes dorsalis — Neurosyphilis causing dorsal column degeneration; impaired vibration/position sense, positive Romberg.
Lead Question - 2012
Nucleus fasciculatus is seen in?
a) Frontal lobe
b) Medulla
c) Temporal lobe
d) Midbrain
Explanation: The dorsal column nuclei (gracilis and cuneatus—sometimes collectively termed “fasciculate” nuclei) lie in the caudal medulla. They receive input from the fasciculi gracilis and cuneatus and send internal arcuate fibers that decussate to form the medial lemniscus. Answer: b) Medulla.
1. Primary sensory modality conveyed by dorsal columns includes:
a) Pain and temperature
b) Fine touch, vibration, proprioception
c) Crude touch only
d) Auditory input
Explanation: Dorsal columns (gracilis, cuneatus) transmit fine touch, vibration, and proprioception. Pain and temperature ascend in the spinothalamic tract. Lesions produce loss of vibration/position sense and positive Romberg sign. Answer: b) Fine touch, vibration, proprioception.
2. Site of sensory decussation for the dorsal column–medial lemniscus pathway:
a) Spinal cord anterior white commissure
b) Caudal medulla (internal arcuate fibers)
c) Pons tegmentum
d) Midbrain colliculi
Explanation: Second-order neurons from nucleus gracilis and cuneatus cross midline as internal arcuate fibers in the caudal medulla, forming the medial lemniscus. Spinothalamic fibers decussate in the spinal cord. Answer: b) Caudal medulla (internal arcuate fibers).
3. The medial lemniscus terminates primarily in:
a) VPL nucleus of thalamus
b) VPM nucleus of thalamus
c) Pulvinar
d) LGB (lateral geniculate body)
Explanation: The medial lemniscus carrying body sensation projects to the VPL thalamus. Face tactile sensation via trigeminal lemniscus reaches VPM. From VPL, third-order neurons ascend to primary somatosensory cortex. Answer: a) VPL nucleus of thalamus.
4. A lesion limited to fasciculus gracilis causes deficits most prominent in the:
a) Ipsilateral upper limb
b) Ipsilateral lower limb
c) Contralateral upper limb
d) Contralateral lower limb
Explanation: Fasciculus gracilis carries input from the ipsilateral lower limb and lower trunk (below T6). Spinal cord dorsal column lesions are ipsilateral to deficits because crossing occurs in the medulla, not the cord. Answer: b) Ipsilateral lower limb.
5. Accessory cuneate nucleus projects to cerebellum via the:
a) Dorsal spinocerebellar tract
b) Cuneocerebellar tract
c) Ventral spinocerebellar tract
d) Rubrospinal tract
Explanation: Proprioceptive input from the upper limb reaches the accessory cuneate nucleus and ascends ipsilaterally via the cuneocerebellar tract to the inferior cerebellar peduncle, informing cerebellar coordination. Answer: b) Cuneocerebellar tract.
6. Clinical: A patient with sensory ataxia, positive Romberg, and impaired vibration in feet most likely has pathology in:
a) Lateral spinothalamic tract
b) Dorsal columns
c) Corticospinal tract only
d) Vestibular nuclei
Explanation: Loss of vibration/position sense with positive Romberg points to dorsal column disease (e.g., B12 deficiency, tabes dorsalis). Spinothalamic lesions cause pain/temperature loss instead. Answer: b) Dorsal columns.
7. In the caudal medulla, the gracile and cuneate tubercles on dorsal surface correspond to:
a) Inferior olivary nuclei
b) Nucleus gracilis and nucleus cuneatus
c) Hypoglossal nucleus only
d) Spinal trigeminal nucleus
Explanation: The dorsal elevations, gracile and cuneate tubercles, overlie the respective dorsal column nuclei, landmarks for the site where internal arcuate fibers originate. Answer: b) Nucleus gracilis and nucleus cuneatus.
8. Stroke of VPL thalamus most characteristically produces:
a) Ipsilateral facial analgesia
b) Contralateral loss of body vibration and proprioception
c) Ipsilateral limb ataxia from cerebellar lesion
d) Bilateral anosmia
Explanation: VPL relays contralateral body somatosensation (including dorsal column modalities). VPM serves face; cerebellar lesions cause ipsilateral ataxia via peduncles. Thus VPL stroke → contralateral tactile/vibration deficits. Answer: b) Contralateral loss of body vibration and proprioception.
9. Subacute combined degeneration (B12 deficiency) initially affects:
a) Anterior horn cells only
b) Dorsal columns and lateral corticospinal tracts
c) Medial longitudinal fasciculus
d) Optic radiations
Explanation: B12 deficiency causes demyelination of dorsal columns (sensory ataxia) and lateral corticospinal tracts (UMN signs). Early recognition prevents irreversible deficits. Answer: b) Dorsal columns and lateral corticospinal tracts.
10. A hemisection (Brown-Séquard) at T10 produces which dorsal column deficit below the lesion?
a) Contralateral loss of vibration/proprioception
b) Ipsilateral loss of vibration/proprioception
c) Bilateral pain loss only
d) No sensory deficit
Explanation: Dorsal column fibers ascend ipsilaterally and cross in the medulla; thus spinal hemisection causes ipsilateral loss of vibration and proprioception below the lesion, with contralateral pain/temperature loss (spinothalamic). Answer: b) Ipsilateral loss of vibration/proprioception.
11. Graphesthesia (recognizing numbers traced on skin) mainly tests integrity of:
a) Dorsal column–medial lemniscus pathway and cortical processing
b) Spinothalamic tract only
c) Vestibulospinal tract
d) Rubrospinal tract
Explanation: Graphesthesia requires intact dorsal column–medial lemniscus input to somatosensory cortex and association areas. Lesions in dorsal columns or parietal cortex impair stereognosis/graphesthesia despite normal strength. Answer: a) Dorsal column–medial lemniscus pathway and cortical processing.
Chapter: Neurophysiology
Topic: Nerve Action Potentials & Nerve Conduction
Subtopic: Compound (Biphasic) Action Potential of Mixed Nerve
Keyword Definitions
Compound action potential (CAP) — Sum of many axons firing; extracellular recording from a mixed nerve; amplitude is graded.
Biphasic recording — Surface electrodes record a negative then positive deflection as the wave passes between and beyond them.
Monophasic recording — One electrode over injured/isoelectric region and one active; produces single main deflection.
All-or-none law — Property of single axons and muscle fibers; not of CAP, which is graded with recruitment.
Refractory period — Time after an AP when axons cannot (absolute) or need stronger stimuli (relative) to fire.
Mixed nerve — Contains myelinated and unmyelinated, motor and sensory fibers with different velocities and thresholds.
Recruitment — Progressive activation of more/larger fibers as stimulus strength increases, enlarging CAP.
Conduction velocity — Distance/time of AP propagation; higher in large, myelinated fibers (saltatory conduction).
Stimulus artifact — Brief deflection from the stimulus itself that precedes the true CAP.
Rheobase/Chronaxie — Minimal current for long duration (rheobase); and duration at 2× rheobase (chronaxie) describing excitability.
Lead Question - 2012
Biphasic action potential of mixed nerve except?
a) All or none phenomenon
b) Two or more positive peaks
c) Refractory period
d) Recorded on surface
Explanation: A compound (biphasic) action potential from a mixed nerve is recorded on the surface and often shows multiple peaks from groups of fibers with differing velocities. Although individual axons obey refractoriness, the CAP as a whole is graded and not all-or-none. Answer: a) All or none phenomenon.
1. CAP amplitude increases with stimulus strength primarily due to:
a) Bigger APs in each axon
b) Recruitment of additional axons
c) Shorter refractory period
d) Lower extracellular resistance
Explanation: Single axon AP size is constant (all-or-none). Increasing stimulus strength excites more axons (especially larger, lower-threshold myelinated fibers first), summating extracellularly to a larger CAP. This is recruitment, not bigger unit APs. Answer: b) Recruitment of additional axons.
2. Multiple peaks in a CAP reflect:
a) Temporal dispersion of fiber groups
b) Alternating depolarization and repolarization of one axon
c) Electrode artifact only
d) Hyperkalemia
Explanation: Mixed nerves contain fast large myelinated and slower small fibers. Their different conduction velocities cause temporal dispersion, producing distinct CAP peaks (e.g., Aα/β then Aδ). It is physiological, not merely artifact. Answer: a) Temporal dispersion of fiber groups.
3. Clinical: In demyelinating neuropathy, a motor nerve study most likely shows:
a) Increased conduction velocity
b) Temporal dispersion and conduction block
c) Higher CAP amplitude with faster latency
d) Normal distal latency
Explanation: Demyelination slows propagation, broadens the CAP (temporal dispersion), and may cause conduction block with reduced amplitude across segments. Distal latency is prolonged; velocity is reduced. Answer: b) Temporal dispersion and conduction block.
4. An extracellular biphasic CAP turns monophasic if:
a) Stimulus intensity is halved
b) One recording electrode is placed over an inactive/lesioned segment
c) Temperature increases
d) Ground electrode is removed
Explanation: Making one electrode indifferent (over electrically silent tissue) converts the recording to monophasic, producing a single main deflection. This is a classic teaching-lab maneuver (crush or ischemic block under one electrode). Answer: b) One recording electrode is placed over an inactive/lesioned segment.
5. Which statement about refractory period in nerve is TRUE?
a) CAP has no refractory behavior at any interval
b) Individual axons have absolute and relative refractory periods
c) Refractoriness depends only on extracellular K+
d) Refractory period occurs only in muscle
Explanation: Each axon shows absolute then relative refractoriness due to Na+ channel inactivation and K+ efflux. CAP refractoriness is less obvious because different axons recover at different times but can be demonstrated with double stimuli. Answer: b) Individual axons have absolute and relative refractory periods.
6. Local anesthetics reduce CAP amplitude by:
a) Blocking voltage-gated Na+ channels
b) Opening Cl− channels
c) Stimulating Na+/K+ pump
d) Inhibiting Ca2+ release from SR
Explanation: Local anesthetics (e.g., lignocaine) bind and block voltage-gated Na+ channels preferentially in small, myelinated pain fibers first, reducing the number of conducting axons and hence CAP amplitude and pain transmission. Answer: a) Blocking voltage-gated Na+ channels.
7. Strength–duration curve: a low chronaxie indicates:
a) Low tissue excitability
b) High tissue excitability
c) Only demyelination
d) Only temperature effect
Explanation: Chronaxie is the pulse duration needed at twice rheobase to excite tissue. Lower chronaxie signifies greater excitability (e.g., large myelinated axons). It is used to compare nerve/muscle excitability in disease and rehabilitation. Answer: b) High tissue excitability.
8. In a nerve conduction lab trace, the earliest deflection after the stimulus is most likely:
a) CAP negative peak
b) Stimulus artifact
c) F-wave
d) H-reflex
Explanation: The stimulus artifact is a brief, non-physiologic deflection due to the stimulus pulse that precedes the true CAP. F-waves and H-reflexes are later, long-loop responses. Recognizing artifact avoids misinterpretation. Answer: b) Stimulus artifact.
9. Cooling a nerve segment will:
a) Increase conduction velocity
b) Decrease conduction velocity and broaden CAP
c) Abolish refractory period
d) Convert biphasic to monophasic
Explanation: Lower temperature slows ion channel kinetics, reducing conduction velocity and increasing temporal dispersion, broadening the CAP. Extreme cooling can block conduction; it does not inherently change recording polarity. Answer: b) Decrease conduction velocity and broaden CAP.
10. Clinical: A patient with acute carpal tunnel shows reduced median motor CAP amplitude distally. This most likely reflects:
a) Primary demyelination only
b) Axonal loss or conduction block at the carpal tunnel
c) Pure muscle disease
d) Increased recruitment
Explanation: Reduced distal CMAP amplitude suggests fewer functioning axons reaching the muscle due to axonal loss or focal conduction block across the entrapment. Demyelination alone typically slows and prolongs latency with relative amplitude preservation. Answer: b) Axonal loss or conduction block at the carpal tunnel.
11. Antidromic sensory study records a larger CAP when:
a) The distance is shorter and fibers are well myelinated
b) The distance is longer only
c) Stimulation is subthreshold
d) Recording is across a joint in extreme flexion
Explanation: Shorter distances reduce temporal dispersion; intact myelination preserves synchrony, yielding larger sensory CAPs. Subthreshold stimulation fails to recruit fibers; joint extremes can compress nerves and reduce amplitude. Answer: a) The distance is shorter and fibers are well myelinated.
Chapter: Neuroanatomy
Topic: Cranial Nerves
Subtopic: Accessory Nerve
Keyword Definitions:
Accessory Nerve: Cranial nerve XI, with spinal and cranial parts.
Cranial Part: Joins vagus nerve to supply palatal, pharyngeal, and laryngeal muscles.
Tensor Veli Palatini: Supplied by mandibular nerve, not accessory nerve.
Palatoglossus: Supplied by cranial part of accessory via vagus.
Palatopharyngeus: Receives motor supply from accessory via vagus.
Tensor Veli Tympani: Supplied by mandibular nerve branch.
Lead Question – 2012
Cranial part of accessory nerve supplies all palatal muscles, EXCEPT?
a) Palatoglossus
b) Palatopharyngeus
c) Tensor veli palatini
d) Tensor veli tympani
Explanation: The cranial part of the accessory nerve joins the vagus nerve to supply most palatal muscles except tensor veli palatini, which is supplied by the mandibular division of the trigeminal nerve. Correct answer: c) Tensor veli palatini.
Question 2. A patient presents with nasal regurgitation after surgery. The most likely injured muscle supplied by cranial accessory nerve is?
a) Palatoglossus
b) Tensor veli palatini
c) Palatopharyngeus
d) Stylopharyngeus
Explanation: Palatopharyngeus elevates the pharynx and closes the nasopharynx during swallowing. Injury leads to nasal regurgitation. Correct answer: c) Palatopharyngeus.
Question 3. Which palatal muscle prevents food from entering the nasopharynx?
a) Tensor veli palatini
b) Palatopharyngeus
c) Palatoglossus
d) Levator veli palatini
Explanation: Levator veli palatini elevates the soft palate to prevent food from entering the nasopharynx during swallowing. Correct answer: d) Levator veli palatini.
Question 4. Which nerve supplies the stylopharyngeus muscle?
a) Glossopharyngeal
b) Accessory
c) Vagus
d) Mandibular
Explanation: Stylopharyngeus is the only muscle supplied by glossopharyngeal nerve (CN IX). Correct answer: a) Glossopharyngeal.
Question 5. In lesion of cranial accessory nerve, which symptom is seen?
a) Hoarseness
b) Tongue deviation
c) Shoulder droop
d) Loss of gag reflex
Explanation: Lesion affects muscles of larynx and pharynx via vagus, leading to hoarseness and dysphagia. Correct answer: a) Hoarseness.
Question 6. A tumor compressing jugular foramen damages which nerves?
a) IX, X, XI
b) VII, IX, XI
c) IX, X, XII
d) X, XI, XII
Explanation: The jugular foramen transmits glossopharyngeal, vagus, and accessory nerves. Correct answer: a) IX, X, XI.
Question 7. A 45-year-old patient has palatal droop and uvula deviation to the right. The lesion is on?
a) Right accessory nerve
b) Left vagus nerve
c) Right glossopharyngeal nerve
d) Left hypoglossal nerve
Explanation: Uvula deviates to the opposite side of lesion due to vagus involvement. Correct answer: b) Left vagus nerve.
Question 8. Which palatal muscle is supplied by mandibular nerve?
a) Tensor veli palatini
b) Levator veli palatini
c) Palatoglossus
d) Palatopharyngeus
Explanation: Tensor veli palatini is the only palatal muscle supplied by mandibular nerve (V3). Correct answer: a) Tensor veli palatini.
Question 9. Injury to spinal accessory nerve leads to weakness of?
a) Sternocleidomastoid and trapezius
b) Masseter and temporalis
c) Levator scapulae and rhomboid
d) Palatoglossus and tensor veli palatini
Explanation: The spinal part of accessory nerve supplies sternocleidomastoid and trapezius. Injury causes shoulder droop and weak head rotation. Correct answer: a) Sternocleidomastoid and trapezius.
Question 10. Which nerve provides motor supply to intrinsic laryngeal muscles (except cricothyroid)?
a) External branch of superior laryngeal nerve
b) Recurrent laryngeal nerve
c) Glossopharyngeal nerve
d) Spinal accessory nerve
Explanation: Recurrent laryngeal nerve, branch of vagus, supplies all intrinsic laryngeal muscles except cricothyroid. Correct answer: b) Recurrent laryngeal nerve.
Question 11. A patient with vagus nerve lesion develops aspiration during swallowing. Which muscle is most affected?
a) Palatopharyngeus
b) Cricopharyngeus
c) Tensor veli palatini
d) Stylopharyngeus
Explanation: Cricopharyngeus (upper esophageal sphincter) controlled by vagus is impaired, leading to aspiration. Correct answer: b) Cricopharyngeus.
Chapter: Head and Neck Anatomy
Topic: Autonomic Nervous System
Subtopic: Otic Ganglion – Location and Relations
Keyword Definitions
Otic ganglion: A parasympathetic ganglion located in the infratemporal fossa, associated with glossopharyngeal nerve.
Foramen ovale: Opening in sphenoid bone transmitting mandibular nerve.
Tensor veli palatini: Muscle of soft palate, medial to otic ganglion.
Mandibular nerve: Main trunk passes lateral to otic ganglion.
Middle meningeal artery: Artery from 1st part of maxillary artery, medial to otic ganglion.
Auriculotemporal nerve: Branch of mandibular nerve carrying secretomotor fibers from otic ganglion to parotid gland.
Glossopharyngeal nerve: Provides preganglionic parasympathetic fibers via lesser petrosal nerve to otic ganglion.
Parasympathetic ganglion: Collection of postganglionic neurons controlling glandular secretion.
Lead Question - 2012
All of the following are true about location of otic ganglia except:
a) Inferior to foramen ovale
b) Lateral to tensor veli palatini
c) Lateral to mandibular nerve
d) Anterior to middle meningeal artery
Explanation: The otic ganglion lies just inferior to foramen ovale, medial to mandibular nerve, and lateral to tensor veli palatini. It is medial, not anterior, to middle meningeal artery. Therefore, the incorrect statement is d) Anterior to middle meningeal artery.
Guessed Question 1
Preganglionic fibers reaching otic ganglion are derived from:
a) Auriculotemporal nerve
b) Chorda tympani
c) Lesser petrosal nerve
d) Facial nerve
Explanation: Preganglionic fibers from glossopharyngeal nerve travel via tympanic branch and lesser petrosal nerve to synapse at otic ganglion. Postganglionic fibers reach parotid gland through auriculotemporal nerve. Correct answer: c) Lesser petrosal nerve.
Guessed Question 2
Secretomotor fibers to parotid gland are carried by:
a) Lingual nerve
b) Buccal nerve
c) Auriculotemporal nerve
d) Inferior alveolar nerve
Explanation: Postganglionic parasympathetic fibers from otic ganglion are carried to the parotid gland by auriculotemporal nerve, a branch of mandibular nerve. Correct answer: c) Auriculotemporal nerve.
Guessed Question 3
A lesion in lesser petrosal nerve would affect secretion of:
a) Sublingual gland
b) Lacrimal gland
c) Submandibular gland
d) Parotid gland
Explanation: Lesser petrosal nerve carries parasympathetic fibers from glossopharyngeal nerve to otic ganglion, essential for parotid gland secretion. Lesion results in dry mouth due to parotid dysfunction. Correct answer: d) Parotid gland.
Guessed Question 4
The otic ganglion is functionally associated with:
a) Facial nerve
b) Hypoglossal nerve
c) Glossopharyngeal nerve
d) Vagus nerve
Explanation: Although anatomically attached to mandibular nerve, the otic ganglion is functionally linked with glossopharyngeal nerve via lesser petrosal branch. Correct answer: c) Glossopharyngeal nerve.
Guessed Question 5
Middle meningeal artery lies in relation to otic ganglion as:
a) Lateral
b) Medial
c) Anterior
d) Posterior
Explanation: The otic ganglion is located medial to the mandibular nerve and lateral to tensor veli palatini, with the middle meningeal artery lying medial to it. Correct answer: b) Medial.
Guessed Question 6
Which nerve carries postganglionic sympathetic fibers through otic ganglion without synapse?
a) Lesser petrosal nerve
b) Glossopharyngeal nerve
c) Auriculotemporal nerve
d) Facial nerve
Explanation: Sympathetic fibers from external carotid plexus pass through otic ganglion without synapsing and reach parotid gland via auriculotemporal nerve. Correct answer: c) Auriculotemporal nerve.
Guessed Question 7
The otic ganglion is located in which fossa?
a) Pterygopalatine fossa
b) Parapharyngeal space
c) Infratemporal fossa
d) Temporal fossa
Explanation: The otic ganglion lies in the infratemporal fossa, just below foramen ovale, closely related to mandibular nerve. Correct answer: c) Infratemporal fossa.
Guessed Question 8
Damage to auriculotemporal nerve after otic ganglion lesion would impair:
a) Lacrimal gland secretion
b) Parotid gland secretion
c) Submandibular gland secretion
d) Sublingual gland secretion
Explanation: Postganglionic fibers from otic ganglion to parotid are transmitted by auriculotemporal nerve. Injury leads to reduced parotid secretion. Correct answer: b) Parotid gland secretion.
Guessed Question 9
Which muscle lies medial to otic ganglion?
a) Masseter
b) Buccinator
c) Tensor veli palatini
d) Temporalis
Explanation: The otic ganglion lies lateral to tensor veli palatini muscle, which forms part of its medial relation. Correct answer: c) Tensor veli palatini.
Guessed Question 10
Which foramen transmits lesser petrosal nerve to otic ganglion?
a) Foramen rotundum
b) Foramen spinosum
c) Foramen ovale
d) Jugular foramen
Explanation: The lesser petrosal nerve passes through foramen ovale to reach otic ganglion in the infratemporal fossa. Correct answer: c) Foramen ovale.
Chapter: Neuroanatomy
Topic: Brainstem nuclei
Subtopic: Nucleus ambiguus
Keyword Definitions
Nucleus ambiguus: Motor nucleus in medulla supplying muscles of pharynx, larynx, and soft palate via CN IX, X, XI.
Cranial nerve IX (Glossopharyngeal): Provides motor fibers to stylopharyngeus and contributes to pharyngeal plexus.
Cranial nerve X (Vagus): Provides motor innervation to laryngeal and pharyngeal muscles.
Cranial nerve XI (Accessory): Cranial root joins vagus to supply pharyngeal and laryngeal muscles.
Cranial nerve XII (Hypoglossal): Purely motor, supplies intrinsic and extrinsic muscles of tongue, not nucleus ambiguus.
Lead Question - 2012
Nucleus ambiguus is not associated with which cranial nerve:
a) X
b) XI
c) IX
d) XII
Explanation: The nucleus ambiguus provides motor innervation via cranial nerves IX, X, and cranial part of XI, controlling swallowing and phonation. Cranial nerve XII (hypoglossal) arises from a separate hypoglossal nucleus, supplying tongue muscles. Hence, the correct answer is d) XII.
Guessed Question 1
A lesion of nucleus ambiguus leads to:
a) Loss of taste
b) Dysphagia
c) Loss of tongue movement
d) Loss of vision
Explanation: Nucleus ambiguus damage causes dysphagia due to paralysis of pharyngeal muscles. Taste is controlled by nucleus solitarius, and tongue movement by hypoglossal nucleus. Therefore, the correct answer is b) Dysphagia.
Guessed Question 2
The cranial root of accessory nerve joins which cranial nerve?
a) IX
b) X
c) XI
d) XII
Explanation: The cranial root of accessory nerve merges with the vagus nerve (X) after emerging from medulla and contributes to pharyngeal and laryngeal innervation. Hence, the correct answer is b) X.
Guessed Question 3
A patient with hoarseness and difficulty swallowing most likely has a lesion affecting:
a) Hypoglossal nucleus
b) Nucleus solitarius
c) Nucleus ambiguus
d) Oculomotor nucleus
Explanation: Hoarseness and dysphagia point to pharyngeal and laryngeal muscle involvement, which are supplied via motor fibers from nucleus ambiguus. Correct answer is c) Nucleus ambiguus.
Guessed Question 4
Stylopharyngeus muscle receives motor fibers from:
a) CN IX
b) CN X
c) CN XI
d) CN XII
Explanation: Stylopharyngeus is the only muscle supplied directly by glossopharyngeal nerve (IX), receiving motor input from nucleus ambiguus. Correct answer is a) CN IX.
Guessed Question 5
Which cranial nerve nucleus is purely motor and controls tongue muscles?
a) Nucleus ambiguus
b) Hypoglossal nucleus
c) Solitary nucleus
d) Dorsal motor nucleus of vagus
Explanation: The hypoglossal nucleus (CN XII) exclusively supplies intrinsic and extrinsic tongue muscles, unlike nucleus ambiguus. Correct answer is b) Hypoglossal nucleus.
Guessed Question 6
Nucleus ambiguus contributes to which reflex?
a) Gag reflex motor limb
b) Light reflex
c) Corneal reflex
d) Pupillary accommodation reflex
Explanation: The motor limb of gag reflex is mediated by vagus via nucleus ambiguus, while the sensory limb is by glossopharyngeal. Correct answer is a) Gag reflex motor limb.
Guessed Question 7
A lesion of vagus nerve involving nucleus ambiguus may cause:
a) Tongue deviation
b) Uvula deviation
c) Jaw deviation
d) Facial palsy
Explanation: Vagus supplies soft palate muscles. Unilateral lesion causes uvula to deviate away from affected side. Correct answer is b) Uvula deviation.
Guessed Question 8
Which muscle is not innervated by nucleus ambiguus?
a) Cricothyroid
b) Pharyngeal constrictors
c) Intrinsic laryngeal muscles
d) Soft palate muscles
Explanation: Cricothyroid is supplied by external branch of superior laryngeal nerve (CN X) but motor nucleus is not nucleus ambiguus. Correct answer is a) Cricothyroid.
Guessed Question 9
Damage to nucleus ambiguus bilaterally can cause:
a) Complete anarthria and aspiration
b) Diplopia
c) Ataxia
d) Loss of smell
Explanation: Bilateral lesions result in paralysis of pharynx and larynx, leading to anarthria and aspiration pneumonia risk. Correct answer is a) Complete anarthria and aspiration.
Guessed Question 10
Motor fibers of vagus nerve arise from:
a) Nucleus solitarius
b) Nucleus ambiguus
c) Dorsal motor nucleus
d) Spinal trigeminal nucleus
Explanation: Motor fibers for pharynx, larynx, and palate in vagus nerve originate from nucleus ambiguus. Dorsal motor nucleus carries parasympathetic fibers. Correct answer is b) Nucleus ambiguus.
Chapter: Neuroanatomy
Topic: Cranial Nerves
Subtopic: Mandibular Nerve (V3) – Branches and Supply
Keyword definitions
Mandibular nerve (V3) — Third division of trigeminal nerve, mixed in function, carrying motor and sensory fibers.
Anterior division — Predominantly motor except for buccal nerve; supplies muscles of mastication (except medial pterygoid).
Posterior division — Mainly sensory, except nerve to mylohyoid which is motor.
Temporalis — Large fan-shaped muscle elevating and retracting mandible; supplied by deep temporal nerves (V3 anterior division).
Masseter — Powerful muscle for mastication; supplied by masseteric nerve (V3 anterior division).
Lateral pterygoid — Protracts mandible; supplied by nerve to lateral pterygoid (V3 anterior division).
Medial pterygoid — Elevates mandible; supplied by nerve to medial pterygoid (from main trunk of V3, not anterior division).
Buccal nerve — Sensory branch from anterior division of V3 supplying cheek mucosa and skin.
Nerve to mylohyoid — Motor branch from inferior alveolar nerve (posterior division) supplying mylohyoid and anterior digastric.
Otic ganglion — Small parasympathetic ganglion functionally related to V3, carrying fibers to parotid gland.
Lead Question - 2012
Which of the following is not supplied by the anterior division of mandibular nerve (V3)?
a) Temporalis
b) Medial pterygoid
c) Lateral pterygoid
d) Masseter
Explanation (50 words): The anterior division of V3 supplies temporalis, masseter, and lateral pterygoid muscles. The medial pterygoid, however, is supplied by the nerve to medial pterygoid, which arises directly from the main trunk of V3 before its anterior and posterior divisions. Answer: b) Medial pterygoid.
1. Which branch of the anterior division of mandibular nerve is purely sensory?
a) Deep temporal nerve
b) Buccal nerve
c) Masseteric nerve
d) Nerve to lateral pterygoid
Explanation (50 words): The buccal nerve is the only sensory branch from the anterior division of V3. It supplies sensation to the mucosa and skin of the cheek, while other branches are motor to muscles of mastication. Answer: b) Buccal nerve.
2. A patient with inability to protract the mandible likely has damage to:
a) Temporalis
b) Masseter
c) Lateral pterygoid
d) Medial pterygoid
Explanation (50 words): The lateral pterygoid is the only muscle of mastication responsible for protraction of the mandible. Damage to its nerve supply (nerve to lateral pterygoid from anterior division of V3) impairs forward movement of the jaw. Answer: c) Lateral pterygoid.
3. Which of the following muscles receives innervation from the nerve to medial pterygoid?
a) Tensor veli palatini
b) Lateral pterygoid
c) Temporalis
d) Masseter
Explanation (50 words): The nerve to medial pterygoid not only supplies the medial pterygoid muscle but also gives twigs to tensor tympani and tensor veli palatini. Answer: a) Tensor veli palatini.
4. Lesion of mandibular nerve at foramen ovale will produce all except:
a) Loss of sensation anterior 2/3 tongue (general)
b) Paralysis of temporalis
c) Loss of taste anterior 2/3 tongue
d) Paralysis of masseter
Explanation (50 words): Mandibular nerve carries general sensation but not taste from the anterior two-thirds of tongue (taste carried by chorda tympani via facial nerve). Hence taste is spared in V3 lesion. Answer: c) Loss of taste anterior 2/3 tongue.
5. The masseteric nerve passes through which structure to reach the masseter?
a) Foramen ovale
b) Mandibular notch
c) Pterygopalatine fossa
d) Infratemporal crest
Explanation (50 words): The masseteric nerve, branch of anterior division of V3, passes laterally through the mandibular notch to enter and supply the masseter muscle. Answer: b) Mandibular notch.
6. A fracture of mandibular condyle damaging the auriculotemporal nerve will cause:
a) Loss of taste
b) Loss of salivary secretion from parotid
c) Paralysis of masseter
d) Inability to protrude mandible
Explanation (50 words): Auriculotemporal nerve carries postganglionic parasympathetic secretomotor fibers from otic ganglion to the parotid gland. Injury reduces parotid secretion, not motor paralysis, as it is a sensory and secretomotor nerve. Answer: b) Loss of salivary secretion from parotid.
7. Which muscle of mastication lies in the temporal fossa and is innervated by deep temporal nerves?
a) Masseter
b) Temporalis
c) Lateral pterygoid
d) Medial pterygoid
Explanation (50 words): Temporalis is a large fan-shaped muscle in the temporal fossa, supplied by anterior and posterior deep temporal nerves from anterior division of V3. Answer: b) Temporalis.
8. Injury to lingual nerve before it is joined by chorda tympani will result in:
a) Loss of general and taste sensation
b) Loss of general sensation only
c) Loss of taste sensation only
d) Loss of salivary secretion only
Explanation (50 words): The lingual nerve carries general sensation from anterior 2/3 tongue. Before joining chorda tympani, it has no taste fibers. Therefore injury causes loss of general sensation only. Answer: b) Loss of general sensation only.
9. The mandibular nerve exits the skull through:
a) Foramen spinosum
b) Foramen ovale
c) Jugular foramen
d) Stylomastoid foramen
Explanation (50 words): The mandibular nerve passes through the foramen ovale to enter the infratemporal fossa where it divides into anterior and posterior divisions. Answer: b) Foramen ovale.
10. Which nerve supplies the mylohyoid and anterior belly of digastric?
a) Lingual nerve
b) Nerve to medial pterygoid
c) Nerve to mylohyoid
d) Buccal nerve
Explanation (50 words): The nerve to mylohyoid is a motor branch of the inferior alveolar nerve (posterior division of V3). It supplies the mylohyoid and anterior belly of digastric muscles. Answer: c) Nerve to mylohyoid.
Chapter: Upper Limb
Topic: Nerve supply of hand
Subtopic: Cutaneous innervation of palm
Keyword definitions
Median nerve — supplies lateral palm, palmar aspect of lateral 3½ fingers, and dorsal tips of the same fingers.
Ulnar nerve — supplies medial 1½ fingers and medial palm and dorsum of hand.
Radial nerve — supplies dorsum of lateral hand, but no palmar branches.
Palmar cutaneous branch — arises from median and ulnar nerves, supplying central and medial palm.
Musculocutaneous nerve — supplies lateral forearm, not palm.
Carpal tunnel — passage for median nerve and flexor tendons beneath flexor retinaculum.
Guyon’s canal — fibro-osseous tunnel for ulnar nerve and artery at wrist.
Dermatomes — C6 supplies thumb, C7 middle finger, C8 little finger.
Thenar eminence — supplied by recurrent branch of median nerve.
Hypothenar eminence — supplied by deep branch of ulnar nerve.
Lead Question - 2012
Sensory supply of the palm is from which nerves -
a) Median nerve and Radial nerve
b) Radial nerve and Ulnar nerve
c) Ulnar nerve and Median nerve
d) Musculocutaneous nerve and Radial nerve
Explanation (50 words): The palm receives sensory innervation mainly from the median and ulnar nerves. Median nerve supplies the lateral 3½ digits and central palm, while ulnar nerve supplies the medial 1½ digits and medial palm. Radial nerve contributes dorsally only. Answer: c) Ulnar nerve and Median nerve.
1. Which nerve is compressed in carpal tunnel syndrome?
a) Ulnar nerve
b) Radial nerve
c) Median nerve
d) Musculocutaneous nerve
Explanation (50 words): Carpal tunnel syndrome results from compression of the median nerve beneath the flexor retinaculum. It causes tingling, numbness, and weakness in the lateral 3½ digits and thenar muscles. Ulnar and radial nerves are unaffected at this site. Answer: c) Median nerve.
2. Sensory loss over hypothenar eminence indicates damage to?
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Axillary nerve
Explanation (50 words): The hypothenar eminence is supplied by the superficial branch of the ulnar nerve. Injury results in sensory loss over medial palm and little finger. Median nerve affects thenar eminence, radial nerve affects dorsum, and axillary nerve supplies shoulder region. Answer: b) Ulnar nerve.
3. Loss of sensation in thumb and index finger palmar aspect indicates lesion of?
a) Median nerve
b) Radial nerve
c) Ulnar nerve
d) Musculocutaneous nerve
Explanation (50 words): The median nerve supplies palmar aspect of thumb, index, middle finger, and radial half of ring finger. A lesion, especially at the wrist, produces sensory loss in these areas. Ulnar supplies medial fingers, radial dorsum, musculocutaneous forearm. Answer: a) Median nerve.
4. Which nerve injury causes sensory loss over dorsum of first web space?
a) Median nerve
b) Radial nerve
c) Ulnar nerve
d) Axillary nerve
Explanation (50 words): The superficial branch of radial nerve supplies dorsum of the first web space. Injury causes sensory loss here without motor deficit. This finding is pathognomonic of radial nerve involvement. Median and ulnar nerves do not supply this area, axillary supplies shoulder. Answer: b) Radial nerve.
5. In claw hand, sensory loss occurs mainly over?
a) Lateral 3½ fingers
b) Medial 1½ fingers
c) Palm center
d) Dorsum first web
Explanation (50 words): Claw hand results from ulnar nerve palsy, producing sensory loss over the medial 1½ fingers and medial palm. Median nerve lesions cause ape thumb and lateral finger sensory loss. Radial lesions affect dorsum, not palm. Answer: b) Medial 1½ fingers.
6. A patient with wrist laceration near pisiform loses sensation over medial palm. Which nerve is cut?
a) Median
b) Ulnar
c) Radial
d) Musculocutaneous
Explanation (50 words): Near pisiform, the ulnar nerve enters the hand via Guyon’s canal. Laceration here damages its superficial branch, producing sensory loss over medial palm and digits. Median nerve supplies lateral palm, radial dorsum, musculocutaneous forearm. Answer: b) Ulnar.
7. Which nerve gives palmar cutaneous branch before carpal tunnel, sparing central palm in CTS?
a) Ulnar nerve
b) Radial nerve
c) Median nerve
d) Musculocutaneous nerve
Explanation (50 words): The median nerve gives off a palmar cutaneous branch proximal to the carpal tunnel. Thus, in carpal tunnel syndrome, the central palm sensation is preserved, though digits are affected. Ulnar and radial also give palmar branches, but this clinical distinction is key for median nerve. Answer: c) Median nerve.
8. A knife injury at medial wrist leads to loss of finger abduction and sensory loss of medial palm. Which nerve is injured?
a) Median
b) Ulnar
c) Radial
d) Axillary
Explanation (50 words): The ulnar nerve supplies interossei (responsible for finger abduction/adduction) and sensory supply to medial palm. Damage at wrist causes motor and sensory loss as described. Median nerve supplies thenar, radial dorsum is radial, axillary shoulder. Answer: b) Ulnar.
9. Which nerve injury leads to loss of precision grip due to loss of thenar sensation and motor supply?
a) Median nerve
b) Ulnar nerve
c) Radial nerve
d) Musculocutaneous nerve
Explanation (50 words): The median nerve supplies thenar muscles (via recurrent branch) and lateral palm. Loss of sensation and motor control causes impaired precision grip, a hallmark of median nerve injury at wrist. Ulnar affects power grip, radial wrist extension, musculocutaneous forearm. Answer: a) Median nerve.
10. Which nerve supplies both dorsal and palmar surfaces of the medial 1½ fingers?
a) Median
b) Radial
c) Ulnar
d) Axillary
Explanation (50 words): The ulnar nerve supplies sensory innervation to medial 1½ fingers on both palmar and dorsal aspects. Median nerve covers lateral fingers, radial dorsum, axillary upper arm. Clinical lesions produce characteristic sensory loss over these areas. Answer: c) Ulnar nerve.
Chapter: Neuroanatomy
Topic: Cranial Nerves
Subtopic: Facial Nerve – Chorda Tympani
Keyword Definitions:
Chorda tympani: Branch of facial nerve carrying taste and parasympathetic fibers.
Preganglionic parasympathetic: Autonomic fibers synapsing in ganglia before reaching target organs.
Postganglionic parasympathetic: Fibers arising from parasympathetic ganglia to supply target organs.
Preganglionic sympathetic: Fibers from spinal cord to sympathetic ganglia.
Postganglionic sympathetic: Fibers from sympathetic ganglia to target structures.
Submandibular ganglion: Parasympathetic ganglion controlling submandibular & sublingual glands.
Lingual nerve: Mandibular nerve branch carrying sensation & taste fibers.
Anterior two-thirds of tongue: Supplied by lingual nerve (general sensation) and chorda tympani (taste).
Facial nerve: 7th cranial nerve carrying motor, sensory, and parasympathetic fibers.
Petrotympanic fissure: Exit point of chorda tympani from middle ear.
Lead Question – 2012
1) What is true about chorda tympani?
a) Postganglionic sympathetic
b) Preganglionic sympathetic
c) Preganglionic parasympathetic
d) Postganglionic parasympathetic
Explanation: The chorda tympani carries preganglionic parasympathetic fibers from the facial nerve to the submandibular ganglion and taste fibers from the anterior two-thirds of the tongue. These parasympathetic fibers later supply submandibular and sublingual glands. Hence, the correct answer is c) Preganglionic parasympathetic.
2) A patient loses taste sensation in the anterior two-thirds of the tongue. The most likely injured structure is:
a) Glossopharyngeal nerve
b) Lingual nerve before joining chorda tympani
c) Chorda tympani
d) Hypoglossal nerve
Explanation: Taste sensation from the anterior two-thirds of the tongue is carried by the chorda tympani via the facial nerve. Loss of this function suggests chorda tympani damage. The glossopharyngeal nerve supplies posterior tongue, while hypoglossal carries only motor fibers. Correct answer: c) Chorda tympani.
3) Parasympathetic fibers from chorda tympani synapse in:
a) Otic ganglion
b) Submandibular ganglion
c) Pterygopalatine ganglion
d) Ciliary ganglion
Explanation: Chorda tympani carries preganglionic parasympathetic fibers that synapse in the submandibular ganglion. Postganglionic fibers then supply the submandibular and sublingual glands. Otic is for parotid, pterygopalatine for lacrimal/nasal, and ciliary for ocular muscles. Correct answer: b) Submandibular ganglion.
4) A lesion at the petrotympanic fissure affects which fibers?
a) General sensory
b) Taste and parasympathetic
c) Purely motor
d) Sympathetic
Explanation: The chorda tympani exits through the petrotympanic fissure, carrying taste and parasympathetic fibers. Damage here results in loss of taste (anterior 2/3 tongue) and reduced salivation. Correct answer: b) Taste and parasympathetic.
5) A patient with dry mouth due to loss of submandibular and sublingual gland secretion likely has a lesion in:
a) Auriculotemporal nerve
b) Lingual nerve after joining chorda tympani
c) Hypoglossal nerve
d) Glossopharyngeal nerve
Explanation: Chorda tympani joins the lingual nerve and carries parasympathetic fibers to submandibular ganglion. Lesion here reduces salivary secretion. Auriculotemporal is for parotid, glossopharyngeal supplies posterior tongue/parotid. Correct answer: b) Lingual nerve after joining chorda tympani.
6) Preganglionic parasympathetic fibers of chorda tympani originate from:
a) Superior salivatory nucleus
b) Inferior salivatory nucleus
c) Edinger–Westphal nucleus
d) Dorsal motor nucleus of vagus
Explanation: Preganglionic parasympathetic fibers of chorda tympani arise from the superior salivatory nucleus in the brainstem. They travel via the facial nerve to synapse in the submandibular ganglion. Correct answer: a) Superior salivatory nucleus.
7) Which nerve carries both taste fibers and parasympathetic fibers to glands?
a) Chorda tympani
b) Greater petrosal nerve
c) Auriculotemporal nerve
d) Hypoglossal nerve
Explanation: The chorda tympani uniquely carries taste (anterior 2/3 tongue) and parasympathetic fibers to submandibular/sublingual glands. Greater petrosal carries parasympathetic for lacrimal/nasal glands but no taste. Correct answer: a) Chorda tympani.
8) Which middle ear structure is closely related to the chorda tympani?
a) Stapes
b) Malleus
c) Incus
d) Tensor tympani
Explanation: The chorda tympani passes through the middle ear, running close to the medial surface of the malleus and incus before exiting. Hence, surgical damage to ossicles may injure it. Correct answer: b) Malleus.
9) A patient with facial nerve palsy sparing lacrimation but with loss of taste (anterior 2/3) has lesion distal to:
a) Geniculate ganglion
b) Stylomastoid foramen
c) Origin of greater petrosal nerve
d) Nucleus ambiguus
Explanation: Taste loss with preserved lacrimation indicates lesion distal to greater petrosal but proximal to chorda tympani origin. This localizes the lesion at/beyond the geniculate ganglion but before stylomastoid foramen. Correct answer: a) Geniculate ganglion.
10) Injury to chorda tympani in middle ear surgery causes:
a) Loss of general sensation posterior tongue
b) Loss of taste anterior tongue and reduced salivation
c) Loss of lacrimation
d) Paralysis of tongue muscles
Explanation: Middle ear surgery can damage chorda tympani, causing loss of taste (anterior 2/3) and decreased salivation from submandibular/sublingual glands. General sensation is lingual nerve, lacrimation via greater petrosal, tongue muscles via hypoglossal. Correct answer: b) Loss of taste anterior tongue and reduced salivation.
11) Which ganglion damage reproduces chorda tympani lesion effects?
a) Submandibular
b) Otic
c) Pterygopalatine
d) Ciliary
Explanation: Submandibular ganglion is the relay site for chorda tympani fibers. Damage here leads to reduced salivation and taste loss, mimicking chorda tympani lesion. Correct answer: a) Submandibular.
Keywords
* Posterior communicating artery (PCOM) — A vessel connecting the internal carotid artery to the posterior cerebral artery, part of the circle of Willis.
* Internal carotid artery (ICA) — Major intracranial artery that gives rise to the ophthalmic, posterior communicating, anterior cerebral, and middle cerebral branches.
* External carotid artery (ECA) — Supplies extracranial head and neck structures; not a primary intracranial circle of Willis branch.
* Middle cerebral artery (MCA) — Continuation of ICA supplying lateral cerebral convexity; important in stroke syndromes.
* Posterior inferior cerebellar artery (PICA) — Branch of vertebral artery supplying posteroinferior cerebellum; related to Wallenberg syndrome.
* Circle of Willis — Collateral arterial anastomotic ring at the base of the brain linking anterior and posterior circulations.
* PCOM aneurysm — Frequent site for saccular aneurysms; may compress oculomotor nerve causing ptosis and pupil changes.
* Oculomotor nerve palsy — Presents with ptosis, "down and out" eye, pupil involvement suggests compressive lesion (e.g., PCOM aneurysm).
* Subarachnoid hemorrhage (SAH) — Sudden severe headache; common presentation of ruptured intracranial saccular aneurysm including PCOM aneurysms.
* Cerebral angiography — Gold standard imaging for diagnosing aneurysms and arterial anatomy; CT angiography is commonly used as initial test.
Chapter: Neuroanatomy — Topic: Cerebral Circulation — Subtopic: Circle of Willis & Posterior Communicating Artery
Lead Question - 2012
Posterior communicating artery a branch of
a) Internal carotid
b) External carotid
c) Middle cerebral
d) Posterior superior cerebellar
Explanation & answer: The posterior communicating artery arises from the internal carotid artery and connects to the posterior cerebral artery, forming part of the circle of Willis. It is not a branch of the external carotid, MCA, or cerebellar arteries. Correct answer: (a) Internal carotid. This artery is clinically important for PCOM aneurysms and oculomotor palsy. (≈50 words)
1.A patient presents with acute third nerve palsy with pupil involvement. Which vascular lesion is most likely?
a) Posterior communicating artery aneurysm
b) Lacunar infarct in the internal capsule
c) Middle cerebral artery thrombosis
d) Superior sagittal sinus thrombosis
Explanation & answer: A compressive PCOM aneurysm classically produces oculomotor nerve palsy with pupil dilation due to parasympathetic fiber compression. Ischemic microvascular palsies typically spare the pupil. MCA stroke causes cortical deficits, not isolated pupil-involving third nerve palsy. Correct answer: (a) Posterior communicating artery aneurysm. (≈50 words)
2. Which artery completes the posterior circulation connection to the anterior circulation via the PCOM?
a) Posterior cerebral artery
b) Anterior communicating artery
c) Basilar artery branch to PICA
d) Superficial temporal artery
Explanation & answer: The PCOM links the internal carotid system anteriorly to the posterior cerebral artery, which arises from the basilar artery posteriorly; this forms part of the posterior-anterior collateral route in the circle of Willis. The anterior communicating artery links the two anterior cerebral arteries. Correct answer: (a) Posterior cerebral artery. (≈50 words)
3. Best noninvasive initial imaging to detect a suspected PCOM aneurysm after SAH is:
a) CT angiography (CTA)
b) Plain skull X-ray
c) Ultrasound Doppler of carotids only
d) Electroencephalogram (EEG)
Explanation & answer: After subarachnoid hemorrhage, CT angiography is a rapid, noninvasive test to visualize intracranial aneurysms including PCOM aneurysms. Digital subtraction cerebral angiography remains gold standard but CTA is commonly used initially for detection and surgical planning. Correct answer: (a) CT angiography (CTA). (≈50 words)
4. Which embryologic vessel contributes to formation of the posterior communicating artery?
a) Fetal carotid-basilar anastomosis
b) Stapedial artery
c) External maxillary artery
d) Vitelline artery
Explanation & answer: The PCOM represents persistence of embryologic carotid–basilar anastomoses connecting the internal carotid to the posterior circulation. These fetal connections normally regress as posterior communicating and posterior cerebral arteries mature. Stapedial and vitelline arteries are unrelated. Correct answer: (a) Fetal carotid-basilar anastomosis. (≈50 words)
5. A ruptured PCOM aneurysm typically causes SAH with blood deposition in which cistern most prominently?
a) Interpeduncular cistern
b) Cisterna magna only
c) Cavernous sinus
d) Sigmoid sinus
Explanation & answer: A PCOM aneurysm rupture often produces subarachnoid blood in the interpeduncular cistern and basal cisterns around the circle of Willis due to its location at the ICA–PCOM junction. Cavernous sinus or venous sinuses are not primary subarachnoid spaces. Correct answer: (a) Interpeduncular cistern. (≈50 words)
6. Which clinical sign suggests a compressive third nerve palsy rather than ischemic microvascular palsy?
a) Early pupil dilation (mydriasis)
b) Isolated finger weakness
c) Pure sensory loss in a dermatomal pattern
d) Pure cerebellar ataxia
Explanation & answer: Pupil-involving oculomotor palsy with early mydriasis points to compression of peripheral parasympathetic fibers, as in a PCOM aneurysm. Microvascular ischemic palsies typically spare the pupil because central somatic fibers are affected but peripheral parasympathetic fibers are preserved. Correct answer: (a) Early pupil dilation (mydriasis). (≈50 words)
7. Which artery is NOT a direct branch of the internal carotid artery in the intracranial segment?
a) Ophthalmic artery (intracranial origin)
b) Posterior communicating artery
c) Middle cerebral artery
d) External carotid artery
Explanation & answer: The external carotid artery is a separate extracranial terminal branch; it does not arise from the intracranial internal carotid. The ophthalmic artery, PCOM, and MCA are intracranial branches or continuations of the ICA. Correct answer: (d) External carotid artery. (≈50 words)
8. In surgical clipping of a PCOM aneurysm, which neural structure must be protected to avoid postoperative diplopia and ptosis?
a) Oculomotor nerve (III)
b) Facial nerve (VII) extracranial branch
c) Hypoglossal nerve (XII)
d) Vagus nerve (X) trunk
Explanation & answer: The oculomotor nerve runs adjacent to the PCOM and posterior cerebral artery; it can be compressed by aneurysms or injured during clipping, causing ptosis and extraocular movement deficits. Facial, hypoglossal, and vagus nerves are remote from the PCOM region. Correct answer: (a) Oculomotor nerve (III). (≈50 words)
9. Which anatomical variation increases risk of anterior circulation collateral failure if PCOM is hypoplastic?
a) Hypoplastic PCOM with inadequate posterior flow
b) Bilateral large PCOM vessels providing robust collateralization
c) Prominent anterior communicating artery bridging ACAs
d) Redundant ophthalmic artery branches
Explanation & answer: A hypoplastic PCOM limits posterior-to-anterior collateral flow, increasing risk of ischemia if ICA flow is compromised. Large bilateral PCOMs or a robust anterior communicating artery improve collateral resilience. Thus hypoplastic PCOM predisposes to collateral failure. Correct answer: (a) Hypoplastic PCOM with inadequate posterior flow. (≈50 words)
10. Which therapeutic option is commonly considered for a saccular PCOM aneurysm not suitable for clipping?
a) Endovascular coiling (with or without stent-assisted technique)
b) Oral anticoagulation alone
c) High-dose systemic corticosteroids only
d) Carotid endarterectomy
Explanation & answer: Endovascular coiling, sometimes stent-assisted, is a standard treatment for saccular intracranial aneurysms including PCOM aneurysms when clipping is unfeasible. Anticoagulation, steroids, or carotid endarterectomy are inappropriate as primary aneurysm treatments. Correct answer: (a) Endovascular coiling. (≈50 words)
Chapter: Autonomic Nervous System
Topic: Coeliac Plexus Block
Subtopic: Clinical Applications
Keywords:
Coeliac Plexus: A nerve plexus located in the upper abdomen around the origin of the celiac trunk, supplying abdominal viscera.
Pain Block: An injection that interrupts pain signals in a specific nerve plexus or pathway.
Retroperitoneal: Anatomical space behind the peritoneum where structures like kidneys and major vessels lie.
Hypotension: Abnormally low blood pressure due to vasodilation or decreased cardiac output.
Diarrhea: Increased frequency of loose stools caused by autonomic imbalance in intestines after nerve block.
Lead Question – 2012
Which of the following is true about coeliac plexus block?
a) Located retroperitoneally at the level of L3
b) Usually done unilaterally
c) Useful for the painful conditions of lower abdomen
d) Most common side effect is diarrhea and hypotension
Explanation: The coeliac plexus lies retroperitoneally at the level of T12–L1, not L3. It is performed bilaterally, not unilaterally. It is mainly useful for pain relief in upper abdominal malignancies such as pancreatic cancer. The most common side effects are diarrhea and hypotension. Answer: d)
Q2. Coeliac plexus block is most commonly indicated in:
a) Renal colic
b) Pancreatic cancer pain
c) Chronic appendicitis
d) Hernia pain
Explanation: Coeliac plexus block is primarily indicated for intractable upper abdominal pain, especially due to pancreatic cancer. It is not used for lower abdominal or somatic pain. Answer: b)
Q3. Which vertebral level corresponds to the coeliac plexus?
a) T6–T7
b) T10–T11
c) T12–L1
d) L3–L4
Explanation: The coeliac plexus is located around the origin of the celiac trunk, corresponding to the vertebral level T12–L1. This location allows innervation to abdominal viscera. Answer: c)
Q4. Which imaging technique is commonly used for coeliac plexus block guidance?
a) MRI
b) Ultrasound
c) CT Scan
d) X-ray
Explanation: CT scan guidance is often used for precise needle placement during coeliac plexus block, ensuring accurate delivery and minimizing complications. Answer: c)
Q5. Which artery is closely related to the coeliac plexus?
a) Superior mesenteric artery
b) Inferior mesenteric artery
c) Celiac trunk
d) Renal artery
Explanation: The coeliac plexus surrounds the origin of the celiac trunk, which arises from the abdominal aorta at T12. This anatomical relation is crucial for block procedure. Answer: c)
Q6. A 50-year-old male with pancreatic cancer undergoes coeliac plexus block. What is the likely immediate effect?
a) Relief of upper abdominal pain
b) Increased heart rate
c) Paralysis of lower limb
d) Relief of pelvic pain
Explanation: Coeliac plexus block specifically reduces visceral pain from upper abdominal organs such as the pancreas, liver, stomach. Answer: a)
Q7. Which is the most serious complication of coeliac plexus block?
a) Diarrhea
b) Hypotension
c) Vascular injury
d) Nausea
Explanation: Though diarrhea and hypotension are common, the most serious complication is vascular injury, which may cause bleeding or ischemia. Answer: c)
Q8. Which sympathetic fibers are mainly targeted in coeliac plexus block?
a) Thoracic splanchnic nerves
b) Lumbar splanchnic nerves
c) Sacral splanchnic nerves
d) Cervical sympathetic trunk
Explanation: The thoracic splanchnic nerves (greater, lesser, least) converge on the coeliac plexus, carrying visceral pain signals. Answer: a)
Q9. A patient develops severe hypotension after a coeliac plexus block. What is the immediate management?
a) IV atropine
b) IV fluids and vasopressors
c) Oral rehydration solution
d) Wait for spontaneous recovery
Explanation: Sudden hypotension results from sympathetic blockade. Management involves IV fluid resuscitation and vasopressors to restore hemodynamic stability. Answer: b)
Q10. Which of the following conditions is least likely to benefit from a coeliac plexus block?
a) Gastric cancer pain
b) Pancreatic cancer pain
c) Chronic pancreatitis pain
d) Acute appendicitis pain
Explanation: Coeliac plexus block is beneficial for chronic visceral pain of upper abdominal organs, but not for somatic pain like acute appendicitis. Answer: d)
Q11. After coeliac plexus block, a patient complains of persistent diarrhea. What is the cause?
a) Parasympathetic overactivity
b) Vagus nerve block
c) Somatic nerve injury
d) Loss of sympathetic inhibition
Explanation: Sympathetic blockade removes inhibitory control over the intestines, leading to unopposed parasympathetic activity and diarrhea. Answer: d)
Chapter: Pelvis and Perineum
Topic: Nerves and Vessels
Subtopic: Relations of Ischial Spine
Keywords:
Ischial spine: A bony projection on the ischium important as a landmark in pelvic anatomy.
Pudendal nerve: Main nerve of perineum, crosses posterior to ischial spine.
Internal pudendal vessels: Artery and vein accompanying pudendal nerve.
Nerve to obturator internus: Motor nerve crossing ischial spine with pudendal bundle.
Obturator nerve: Runs along lateral pelvic wall, does not cross ischial spine.
Lead Question - 2012
Structure crossing dorsal surface of ischial spine are A/E:
a) Internal pudendal vessel
b) Pudendal nerve
c) Obturator nerve
d) Nerve to obturator internus
Explanation: The pudendal nerve, internal pudendal vessels, and nerve to obturator internus cross the ischial spine. The obturator nerve runs along the pelvic sidewall and exits via obturator canal, not over the ischial spine. Answer: c) Obturator nerve
1) A 35-year-old female during childbirth suffered injury to the structure crossing the ischial spine. Which function is most likely affected?
a) Sensation of perineum
b) Hip adduction
c) Quadriceps contraction
d) Knee extension
Explanation: The pudendal nerve crosses ischial spine and provides sensory supply to perineum. Injury causes perineal sensory loss. Hip adduction involves obturator nerve which does not cross spine. Answer: a) Sensation of perineum
2) Which vessel accompanies pudendal nerve while crossing ischial spine?
a) Inferior gluteal artery
b) Internal pudendal artery
c) Superior gluteal artery
d) Obturator artery
Explanation: Pudendal nerve crosses ischial spine along with internal pudendal vessels. Inferior and superior gluteal arteries do not directly cross spine. Answer: b) Internal pudendal artery
3) A surgeon performing pudendal block locates which landmark near ischial spine?
a) Sacral promontory
b) Coccyx tip
c) Ischial spine via vaginal exam
d) Iliac crest
Explanation: Pudendal block is given by palpating ischial spine transvaginally where pudendal nerve passes. Coccyx and iliac crest are not related landmarks. Answer: c) Ischial spine via vaginal exam
4) Which nerve does not cross ischial spine?
a) Pudendal nerve
b) Nerve to obturator internus
c) Internal pudendal vessels
d) Obturator nerve
Explanation: Obturator nerve runs through obturator canal and does not cross ischial spine. Others cross spine dorsally. Answer: d) Obturator nerve
5) Pudendal nerve block provides anesthesia for which procedure?
a) Episiotomy
b) Appendectomy
c) Inguinal hernia repair
d) Cholecystectomy
Explanation: Pudendal block is mainly used in obstetrics for episiotomy and perineal repair by anesthetizing pudendal nerve at ischial spine. Answer: a) Episiotomy
6) Nerve to obturator internus after crossing ischial spine enters which region?
a) Perineum
b) Gluteal region
c) Obturator canal
d) Femoral canal
Explanation: The nerve to obturator internus crosses the ischial spine dorsally and enters the gluteal region before supplying obturator internus muscle. Answer: b) Gluteal region
7) Which muscle acts as close relation of structures crossing ischial spine?
a) Piriformis
b) Coccygeus
c) Obturator externus
d) Psoas major
Explanation: Coccygeus muscle lies in relation to ischial spine, providing support to crossing pudendal bundle. Piriformis is higher, obturator externus and psoas are not related. Answer: b) Coccygeus
8) Clinical feature of pudendal nerve entrapment near ischial spine is:
a) Loss of knee reflex
b) Perineal pain and numbness
c) Foot drop
d) Loss of Achilles reflex
Explanation: Pudendal entrapment near ischial spine causes perineal pain, numbness, and sphincter dysfunction. Reflexes and foot drop are unrelated. Answer: b) Perineal pain and numbness
9) In pelvic fracture involving ischial spine, which function is spared?
a) Perineal sensation
b) Anal sphincter tone
c) Hip adduction
d) External urethral sphincter
Explanation: Hip adduction is mediated by obturator nerve, which does not cross ischial spine, hence spared. Pudendal functions are compromised. Answer: c) Hip adduction
10) The pudendal nerve is derived from which spinal segments?
a) L2-L4
b) L4-S1
c) S2-S4
d) S1-S3
Explanation: Pudendal nerve originates from sacral plexus segments S2, S3, S4. These supply perineum and external sphincters. Answer: c) S2-S4
Chapter: Abdomen
Topic: Autonomic Nervous System of Abdomen
Subtopic: Celiac Plexus Block
Keyword Definitions:
Celiac Plexus: A network of nerves around the abdominal aorta supplying abdominal viscera.
Retrocrural Approach: Classic posterior approach to reach the celiac plexus.
Visceral Pain: Pain arising from internal organs, often dull and poorly localized.
Hypotension: Decrease in blood pressure, common after sympathetic block.
Anesthesia vs Analgesia: Anesthesia blocks sensation including touch and pain, while analgesia only blocks pain.
Lead Question – 2012
Celiac plexus block all the following is true except?
a) Relieved pain from gastric malignancy
b) Cause hypotention
c) Can be used to provide anesthesia for intra abdominal surgery
d) Can be given only by retrocrural (classic) approach
Explanation: The celiac plexus block is useful for pain relief in gastric and pancreatic malignancy and may cause hypotension due to sympathetic block. It is not used to provide complete anesthesia for intra-abdominal surgery. Multiple approaches (retrocrural, anterior, endoscopic) exist, so option c is correct.
Guessed Questions for NEET PG:
1) Celiac plexus block is most commonly used for pain relief in:
a) Chronic appendicitis
b) Pancreatic cancer
c) Gallbladder stones
d) Peptic ulcer disease
Explanation: Pancreatic cancer produces severe intractable pain, which is effectively relieved by celiac plexus block. It reduces narcotic use and improves quality of life. Hence option b is correct.
2) Complication of celiac plexus block includes:
a) Hypertension
b) Hypotension
c) Tachycardia
d) None of the above
Explanation: The sympathetic fibers in the celiac plexus regulate vascular tone. Their block causes vasodilation and hypotension, not hypertension. Tachycardia may be compensatory, but main complication is hypotension. Answer: b.
3) Approach not used for celiac plexus block:
a) Retrocrural
b) Anterior transabdominal
c) Endoscopic ultrasound-guided
d) Transoral
Explanation: The block can be done by retrocrural (classic posterior), anterior percutaneous, or endoscopic methods. Transoral is not a described route. Hence option d is correct.
4) Which type of nerve fibers are blocked by celiac plexus block?
a) Parasympathetic
b) Sympathetic
c) Somatic sensory
d) Motor
Explanation: The celiac plexus contains sympathetic fibers supplying abdominal viscera. Blocking these fibers reduces visceral pain. Parasympathetic and somatic motor fibers remain unaffected. Hence option b is correct.
5) A patient with unresectable pancreatic carcinoma complains of severe epigastric pain. Best palliative option is:
a) Celiac plexus block
b) Cholecystectomy
c) Gastrectomy
d) Splenectomy
Explanation: Celiac plexus block provides long-term relief of upper abdominal visceral pain, especially in pancreatic carcinoma. Surgical options are not indicated. Answer: a.
6) Hypotension after celiac plexus block occurs due to:
a) Increased vagal tone
b) Sympathetic blockade and vasodilation
c) Blood loss
d) Reflex bradycardia
Explanation: Sympathetic blockade leads to vasodilation of splanchnic vessels, reducing systemic vascular resistance and causing hypotension. Hence option b is correct.
7) Duration of analgesia after celiac plexus block using alcohol is:
a) Few hours
b) Days
c) Weeks to months
d) Lifetime
Explanation: Neurolytic agents like alcohol or phenol produce long-lasting destruction of sympathetic fibers, giving pain relief for weeks to months. Answer: c.
8) Clinical sign of successful celiac plexus block:
a) Increased heart rate
b) Warmth and vasodilation in lower limbs
c) Warmth and vasodilation in upper abdomen
d) Sweating in face
Explanation: Blocking sympathetic fibers causes vasodilation in splanchnic circulation, presenting as warmth in the upper abdomen. Thus option c is correct.
9) Contraindication for celiac plexus block:
a) Coagulopathy
b) Chronic pain of pancreas
c) Severe malignancy pain
d) Endoscopic procedure planned
Explanation: Coagulopathy increases the risk of retroperitoneal hemorrhage, hence is a contraindication. Chronic pain and malignancy are indications. Answer: a.
10) A patient undergoing celiac plexus block develops sudden severe back pain with leg weakness. Most likely cause is:
a) Alcohol neurotoxicity to somatic nerves
b) Hypotension
c) Pneumothorax
d) Allergy
Explanation: Neurolytic agents may spread to somatic nerves like lumbar plexus, leading to back pain and transient leg weakness. Hence option a is correct.
Chapter: Anatomy
Topic: Nerves of Perineum
Subtopic: Ischiorectal Abscess and Nerve Supply
Keyword Definitions:
Ischiorectal Abscess: A pus collection in ischiorectal fossa, usually due to anal gland infection.
Inferior Rectal Nerve: Branch of pudendal nerve, supplies external anal sphincter and perianal skin.
Superior Rectal Nerve: Branch of inferior mesenteric plexus, supplies rectal mucosa.
Inferior Gluteal Nerve: Supplies gluteus maximus muscle.
Superior Gluteal Nerve: Supplies gluteus medius, minimus, tensor fascia lata.
Pudendal Nerve: Main nerve of perineum, gives inferior rectal branches.
Clinical Correlation: Abscess drainage can damage inferior rectal nerve causing anal incontinence.
Lead Question – 2012
During incision & drainage of ischiorectal abscess, which nerve is/are affected/injured:
a) Superior rectal nerve
b) Inferior rectal nerve
c) Superior gluteal nerve
d) Inferior gluteal nerve
Explanation: The ischiorectal fossa contains branches of pudendal nerve, mainly inferior rectal nerves. Incision and drainage can damage these nerves, leading to sensory loss in perianal skin and possible sphincter dysfunction. Correct answer: Inferior rectal nerve.
Guessed Questions for NEET PG
Q1. Which structure forms the medial boundary of the ischiorectal fossa?
a) Levator ani
b) Obturator internus
c) Gluteus maximus
d) Piriformis
Explanation: The ischiorectal fossa lies between levator ani medially and obturator internus laterally. Medial boundary is levator ani muscle, covered by anal fascia. Correct answer: Levator ani.
Q2. A patient with ischiorectal abscess drainage later develops perianal sensory loss. The most likely injured nerve is:
a) Superior hypogastric plexus
b) Inferior rectal nerve
c) Sciatic nerve
d) Coccygeal plexus
Explanation: Perianal sensory loss after ischiorectal abscess surgery indicates inferior rectal nerve injury, which supplies perianal skin and external sphincter. Correct answer: Inferior rectal nerve.
Q3. Inferior rectal nerve is a branch of:
a) Pudendal nerve
b) Obturator nerve
c) Sacral plexus directly
d) Coccygeal nerve
Explanation: The inferior rectal nerve arises from the pudendal nerve, providing motor supply to external anal sphincter and sensory supply to perianal skin. Correct answer: Pudendal nerve.
Q4. Which vessel accompanies the inferior rectal nerve in the ischiorectal fossa?
a) Superior rectal artery
b) Middle rectal artery
c) Inferior rectal artery
d) Internal pudendal artery
Explanation: The inferior rectal nerve is accompanied by inferior rectal vessels, branches of internal pudendal vessels, within the ischiorectal fossa. Correct answer: Inferior rectal artery.
Q5. A 40-year-old with ischiorectal abscess presents with fecal incontinence post-surgery. Which muscle is most likely affected?
a) Internal anal sphincter
b) External anal sphincter
c) Puborectalis
d) Levator ani
Explanation: The inferior rectal nerve supplies external anal sphincter. Injury causes sphincter weakness leading to incontinence. Correct answer: External anal sphincter.
Q6. The pudendal nerve exits the pelvis through:
a) Greater sciatic foramen
b) Lesser sciatic foramen
c) Obturator canal
d) Sacral hiatus
Explanation: Pudendal nerve exits pelvis via greater sciatic foramen, curves around sacrospinous ligament, and enters perineum through lesser sciatic foramen. Correct answer: Greater sciatic foramen.
Q7. Which nerve is spared in ischiorectal abscess incision?
a) Inferior rectal nerve
b) Superior gluteal nerve
c) Perineal branch of posterior femoral cutaneous
d) Pudendal nerve
Explanation: Superior gluteal nerve is high in gluteal region, away from perianal surgery. Hence, spared in ischiorectal abscess drainage. Correct answer: Superior gluteal nerve.
Q8. Clinical sign of inferior rectal nerve damage is:
a) Loss of rectal mucosal sensation
b) Weakness of internal sphincter
c) Fecal incontinence
d) Urinary incontinence
Explanation: Inferior rectal nerve supplies external sphincter; injury leads to fecal incontinence, not urinary. Correct answer: Fecal incontinence.
Q9. Which of the following is NOT located in the ischiorectal fossa?
a) Fat
b) Inferior rectal vessels
c) Inferior rectal nerve
d) Superior rectal nerve
Explanation: Superior rectal nerve is from inferior mesenteric plexus and lies higher, not in ischiorectal fossa. Correct answer: Superior rectal nerve.
Q10. During perianal surgery, surgeon avoids deep lateral dissection to prevent injury to:
a) Pudendal canal structures
b) Sciatic nerve
c) Inferior gluteal nerve
d) Coccygeal plexus
Explanation: Pudendal canal contains pudendal nerve and internal pudendal vessels; deep lateral dissection risks injury. Correct answer: Pudendal canal structures.
Topic: Cavernous Sinus
Subtopic: Structures within the Cavernous Sinus
Keyword Definitions:
Cavernous Sinus: A venous sinus located on either side of the pituitary fossa, containing cranial nerves and the internal carotid artery.
Internal Carotid Artery: Artery passing through cavernous sinus, giving off ophthalmic artery and sympathetic plexus.
Oculomotor Nerve (CN III): Passes through lateral wall of cavernous sinus, controls most extraocular muscles.
Trochlear Nerve (CN IV): Lies in lateral wall, innervates superior oblique muscle.
Ophthalmic Nerve (V1): Branch of trigeminal nerve in lateral wall, sensory to upper face and cornea.
Maxillary Nerve (V2): Passes in lateral wall, sensory to midface, upper teeth.
Mandibular Nerve (V3): Does not pass through cavernous sinus; exits skull via foramen ovale.
Abducens Nerve (CN VI): Runs through sinus near ICA, controls lateral rectus muscle.
Facial Nerve (CN VII): Not present in cavernous sinus; exits via stylomastoid foramen.
Clinical Relevance: Cavernous sinus thrombosis affects cranial nerves III, IV, V1, V2, VI and internal carotid artery.
Lead Question – 2012
Which of the following structures seen in the cavernous sinus?
a) Maxillary division of V nerve
b) Mandibular division of V nerve
c) Internal carotid artery
d) Facial nerve
Explanation: The internal carotid artery courses through the cavernous sinus along with cranial nerves III, IV, V1, V2 (maxillary), and VI. The mandibular nerve (V3) and facial nerve (CN VII) are not present. Therefore, the correct answer is c) Internal carotid artery. Understanding anatomy is critical in cavernous sinus thrombosis and aneurysms.
1. Which cranial nerve passes through the lateral wall of the cavernous sinus?
a) Abducens (CN VI)
b) Oculomotor (CN III)
c) Mandibular (V3)
d) Facial (CN VII)
Explanation: Cranial nerves III, IV, V1, and V2 pass in the lateral wall of the cavernous sinus. CN VI runs centrally near ICA. Mandibular (V3) and facial nerve do not traverse the sinus. Correct answer: b) Oculomotor (CN III).
2. Abducens nerve (CN VI) is located:
a) In lateral wall
b) Medial to ICA
c) Outside sinus
d) With facial nerve
Explanation: The abducens nerve (CN VI) runs adjacent to the internal carotid artery within the sinus. It is most vulnerable in cavernous sinus thrombosis. Correct answer: b) Medial to ICA.
3. Which trigeminal branch passes through cavernous sinus?
a) Ophthalmic (V1)
b) Maxillary (V2)
c) Mandibular (V3)
d) Both a and b
Explanation: V1 (ophthalmic) and V2 (maxillary) traverse the lateral wall of cavernous sinus, providing sensory innervation to face. V3 exits via foramen ovale, outside sinus. Correct answer: d) Both a and b.
4. Facial nerve (CN VII) exits skull through:
a) Foramen ovale
b) Jugular foramen
c) Stylomastoid foramen
d) Superior orbital fissure
Explanation: The facial nerve (CN VII) exits via stylomastoid foramen, not through cavernous sinus. Lesions in sinus do not affect CN VII. Correct answer: c) Stylomastoid foramen.
5. Cavernous sinus thrombosis can affect all EXCEPT:
a) CN III
b) CN IV
c) CN VII
d) CN VI
Explanation: Thrombosis of cavernous sinus involves CN III, IV, V1, V2, and VI. CN VII (facial nerve) is not affected because it is outside the sinus. Correct answer: c) CN VII.
6. Internal carotid artery in cavernous sinus gives off:
a) Ophthalmic artery
b) Maxillary artery
c) Middle cerebral artery
d) Vertebral artery
Explanation: The internal carotid artery within cavernous sinus gives rise to ophthalmic artery and branches to carotid sympathetic plexus. Middle cerebral and vertebral arteries arise more proximally. Correct answer: a) Ophthalmic artery.
7. Superior orbital fissure transmits which structures in relation to cavernous sinus?
a) CN III, IV, V1, VI
b) V2 and V3
c) CN VII and VIII
d) ICA only
Explanation: Cranial nerves III, IV, V1, VI leave the cavernous sinus to enter orbit through superior orbital fissure. This pathway explains clinical ophthalmoplegia in cavernous sinus lesions. Correct answer: a) CN III, IV, V1, VI.
8. Maxillary nerve (V2) exits skull via:
a) Foramen rotundum
b) Foramen ovale
c) Superior orbital fissure
d) Jugular foramen
Explanation: Maxillary nerve (V2) passes through lateral wall of cavernous sinus and exits via foramen rotundum to reach pterygopalatine fossa. Correct answer: a) Foramen rotundum.
9. Mandibular nerve (V3) is located:
a) Within cavernous sinus
b) Exits via foramen ovale
c) Lateral wall of sinus
d) With CN VI
Explanation: The mandibular nerve (V3) does not traverse the cavernous sinus. It exits skull via foramen ovale to supply lower face and muscles of mastication. Correct answer: b) Exits via foramen ovale.
10. Cavernous sinus is clinically important in:
a) Spread of facial infections
b) Thrombosis causing cranial nerve palsies
c) ICA aneurysms
d) All of the above
Explanation: The cavernous sinus is prone to thrombosis from facial infections (danger triangle), can compress CN III, IV, V1, V2, VI, and ICA aneurysms can occur. Clinical knowledge is crucial. Correct answer: d) All of the above.
Sympathetic Nervous System: Part of the autonomic nervous system responsible for 'fight or flight' responses.
Cardiac Sympathetic Supply: Nerves arising from thoracic spinal segments innervating the heart, increasing heart rate and contractility.
Spinal Segments: Sections of the spinal cord from which sympathetic fibers emerge (T1–L2).
SA Node: Sinoatrial node, pacemaker of the heart, receives sympathetic and parasympathetic innervation.
AV Node: Atrioventricular node, conduction relay, also influenced by autonomic inputs.
Thoracic Sympathetic Chain: Series of ganglia along thoracic vertebrae transmitting sympathetic fibers to organs including the heart.
Chapter: Cardiovascular Physiology
Topic: Autonomic Nervous Supply of Heart
Subtopic: Sympathetic Innervation
Lead Question 2012: Sympathetic supply to the heart arises from which of the following spinal segments?
a) T1 to T5
b) T2 to T6
c) T3 to T7
d) T4 to T8
Answer: a) T1 to T5
Explanation: Cardiac sympathetic fibers arise from the thoracic spinal segments T1 to T5. These preganglionic fibers synapse in the sympathetic chain and postganglionic fibers reach the SA node, AV node, and coronary vessels. They increase heart rate, contractility, and conduction velocity. Understanding this is crucial in autonomic cardiac physiology and clinical conditions like referred cardiac pain.
1. Which part of the autonomic nervous system increases heart rate?
a) Parasympathetic
b) Sympathetic
c) Enteric
d) Somatic
Answer: b) Sympathetic
Explanation: Sympathetic stimulation increases heart rate, contractility, and conduction through SA and AV nodes. Parasympathetic (vagal) stimulation decreases heart rate. This balance is essential for cardiac homeostasis and is clinically important in arrhythmias and heart failure.
2. Preganglionic sympathetic fibers to the heart synapse in which ganglia?
a) Cervical ganglia
b) Thoracic sympathetic chain
c) Dorsal root ganglia
d) Celiac ganglia
Answer: b) Thoracic sympathetic chain
Explanation: Preganglionic fibers from T1–T5 synapse in the thoracic sympathetic chain. Postganglionic fibers then reach cardiac structures. This pathway is clinically significant for cardiac sympathectomy and management of arrhythmias.
3. Sympathetic stimulation affects which part of the heart first?
a) SA node
b) AV node
c) Ventricular myocardium
d) Aorta
Answer: a) SA node
Explanation: Sympathetic fibers primarily influence the SA node, increasing heart rate. AV node conduction and ventricular contractility are also enhanced, demonstrating the widespread effect of sympathetic innervation on cardiac function.
4. Referred cardiac pain is transmitted through which spinal segments?
a) T1–T5
b) C3–C5
c) L1–L3
d) S1–S3
Answer: a) T1–T5
Explanation: Sympathetic afferents from the heart enter spinal cord segments T1–T5, producing referred pain in the chest and medial arm during myocardial ischemia. Knowledge of this pathway aids in diagnosing angina or myocardial infarction.
5. Which neurotransmitter is released by postganglionic sympathetic fibers at the heart?
a) Acetylcholine
b) Norepinephrine
c) Dopamine
d) Serotonin
Answer: b) Norepinephrine
Explanation: Postganglionic sympathetic fibers release norepinephrine, which binds to beta-1 adrenergic receptors, increasing heart rate and contractility. Pharmacologic modulation of this pathway is important in heart failure and arrhythmia management.
6. Sympathetic cardiac nerves also innervate which coronary structures?
a) Coronary arteries
b) Pulmonary veins
c) Aorta only
d) SA node exclusively
Answer: a) Coronary arteries
Explanation: Sympathetic nerves innervate coronary vessels, causing vasodilation via beta-2 receptors during increased cardiac activity, ensuring adequate myocardial perfusion during stress or exercise.
7. Beta-1 adrenergic receptors are predominantly located on:
a) SA and AV nodes
b) Smooth muscle of arteries
c) Lung alveoli
d) Skeletal muscle
Answer: a) SA and AV nodes
Explanation: Beta-1 receptors are located on nodal tissue and ventricular myocardium, mediating sympathetic effects like increased heart rate and conduction velocity. Beta-blockers act here to treat tachyarrhythmias and hypertension.
8. Cardiac sympathectomy may be performed to treat:
a) Refractory angina
b) GERD
c) Asthma
d) Liver cirrhosis
Answer: a) Refractory angina
Explanation: Cardiac sympathectomy reduces sympathetic input, lowering heart rate and oxygen demand in severe angina. T1–T5 segments are targeted to interrupt sympathetic supply while preserving parasympathetic tone.
9. Which spinal levels contribute to sympathetic innervation of both SA and AV nodes?
a) T1–T5
b) C1–C4
c) L1–L3
d) T6–T10
Answer: a) T1–T5
Explanation: Preganglionic fibers from T1–T5 synapse in the cervical and upper thoracic ganglia. Postganglionic fibers innervate both SA and AV nodes, coordinating cardiac rate and conduction, essential knowledge for cardiology exams.
10. Increased sympathetic activity to the heart results in:
a) Tachycardia and increased contractility
b) Bradycardia and decreased contractility
c) Vasodilation of systemic veins
d) No change in cardiac function
Answer: a) Tachycardia and increased contractility
Explanation: Sympathetic activation increases SA node firing rate, AV conduction, and myocardial contractility through norepinephrine action on beta-1 receptors. This response supports cardiac output during stress and is a core concept in autonomic cardiac physiology.
Chapter: Musculoskeletal Anatomy
Topic: Lower Limb Anatomy
Sub-topic: Gluteal Region – Muscles, Nerves, and Safe Injection Sites
Keyword Definitions:
Gluteus maximus: The largest muscle in the buttock, responsible for hip extension and external rotation.
Gluteus medius: A muscle important for hip abduction, covering part of the safe injection site.
Sciatic nerve: Major nerve running through the posterior thigh, can be injured by improper injection.
Safe injection site: The superolateral quadrant of the buttock to avoid nerve or vascular injury.
Trendelenburg gait: Abnormal gait caused by injury to the superior gluteal nerve.
Superior gluteal nerve: Nerve that supplies gluteus medius, gluteus minimus, and tensor fasciae latae.
Inferior gluteal nerve: Supplies the gluteus maximus muscle.
Intramuscular injection: Administration of drugs into the muscle tissue for rapid absorption.
Quadrants of buttock: Divisions used to identify safe anatomical injection sites.
Ischial tuberosity: Bony prominence of pelvis, landmark for hamstring muscle attachment.
1. Site of injection in the gluteus? (2012)
a) Inferomedial
b) Superomedial
c) Superolateral
d) Superomedial
Explanation: The correct answer is c) Superolateral. Intramuscular injections in the gluteal region should be given in the superolateral quadrant to avoid injury to the sciatic nerve and major vessels. This quadrant lies over the gluteus medius, which has good muscle bulk and minimal risk of nerve damage. Choosing other quadrants risks nerve injury or hematoma formation.
2. Which nerve is most at risk if a gluteal intramuscular injection is given in the inferomedial quadrant?
a) Femoral nerve
b) Sciatic nerve
c) Obturator nerve
d) Pudendal nerve
Explanation: The correct answer is b) Sciatic nerve. The sciatic nerve passes through the lower and medial portions of the gluteal region. Improper injections here can cause severe neuropathic pain, weakness in the leg, and even permanent paralysis in severe cases. Hence, the inferomedial quadrant is strictly avoided for injections.
3. A patient develops Trendelenburg gait after hip surgery. Which nerve was likely injured?
a) Superior gluteal nerve
b) Inferior gluteal nerve
c) Sciatic nerve
d) Femoral nerve
Explanation: The correct answer is a) Superior gluteal nerve. This nerve innervates gluteus medius and minimus. Injury leads to weakness in hip abduction, causing the pelvis to drop on the opposite side during walking. This is commonly tested clinically and can occur after injections or surgery near the greater sciatic foramen.
4. Which muscle is primarily used for safe gluteal intramuscular injections?
a) Gluteus maximus
b) Gluteus medius
c) Piriformis
d) Tensor fasciae latae
Explanation: The correct answer is b) Gluteus medius. The muscle has a thick bulk in the superolateral quadrant, providing a safe site for intramuscular injections while avoiding important neurovascular structures. Gluteus maximus is avoided due to the underlying sciatic nerve pathway.
5. The piriformis muscle exits the pelvis through which structure?
a) Lesser sciatic foramen
b) Greater sciatic foramen
c) Obturator canal
d) Inguinal canal
Explanation: The correct answer is b) Greater sciatic foramen. The piriformis muscle is a key landmark in the gluteal region, dividing the greater sciatic foramen into superior and inferior parts for neurovascular structures. Its relationship is clinically important in avoiding nerve injury during injections.
6. Which artery accompanies the sciatic nerve in the gluteal region?
a) Inferior gluteal artery
b) Superior gluteal artery
c) Obturator artery
d) Femoral artery
Explanation: The correct answer is a) Inferior gluteal artery. This artery, along with the sciatic nerve, exits the pelvis below the piriformis. Injury to this artery during wrong injection placement can cause significant hematoma formation.
7. Which nerve passes above the piriformis muscle?
a) Sciatic nerve
b) Superior gluteal nerve
c) Inferior gluteal nerve
d) Pudendal nerve
Explanation: The correct answer is b) Superior gluteal nerve. It exits the pelvis above piriformis and is at risk in superomedial injections, leading to Trendelenburg gait. This is why even the superomedial quadrant is avoided for injections.
8. A patient complains of buttock pain radiating down the thigh after a fall. Which nerve is most likely injured?
a) Sciatic nerve
b) Femoral nerve
c) Obturator nerve
d) Pudendal nerve
Explanation: The correct answer is a) Sciatic nerve. This nerve supplies the posterior thigh and all muscles below the knee. Injury causes pain, weakness, and sensory loss along its distribution. It is the most commonly injured nerve in the gluteal region from trauma or improper injections.
9. Which muscle is innervated by the inferior gluteal nerve?
a) Gluteus maximus
b) Gluteus medius
c) Gluteus minimus
d) Piriformis
Explanation: The correct answer is a) Gluteus maximus. This muscle is important for hip extension, especially in rising from sitting or climbing stairs. Injury to its nerve reduces hip extension power but does not affect walking significantly.
10. Which landmark is used to locate the superolateral gluteal injection site?
a) Anterior superior iliac spine and greater trochanter
b) Ischial tuberosity and coccyx
c) Pubic symphysis and femoral head
d) Sacrum and iliac crest
Explanation: The correct answer is a) Anterior superior iliac spine and greater trochanter. Drawing an imaginary line between these two landmarks and selecting the upper outer quadrant ensures safe injection placement.
Keyword Definitions:
Tibial Nerve: A branch of the sciatic nerve that innervates the posterior compartment of the leg and plantar surface of the foot.
Palsy: Weakness or paralysis of a muscle group due to nerve damage.
Plantar Flexion: Movement of the foot downward at the ankle joint.
Dorsiflexion: Upward movement of the foot at the ankle joint.
Anterior Compartment of Leg: Muscles responsible for dorsiflexion of the foot and extension of the toes.
Posterior Compartment of Leg: Muscles responsible for plantar flexion and toe flexion.
Sciatic Nerve: Largest nerve in the body, branching into tibial and common peroneal nerves.
Medial Plantar Nerve: Branch of the tibial nerve supplying the medial aspect of the sole.
Lateral Plantar Nerve: Branch of the tibial nerve supplying the lateral aspect of the sole.
Clinical Examination: Bedside evaluation of nerve injury using motor, sensory, and reflex testing.
Chapter: Neuroanatomy Topic: Peripheral Nervous System Subtopic: Tibial Nerve Injury
Lead Question (2012):
Tibial nerve injury/palsy causes:
a) Dorsiflexion of foot at ankle joint
b) Plantar flexion of the foot at ankle joint
c) Loss of sensation of dorsum of foot
d) Paralysis of muscles of anterior compartment of leg
Explanation: The tibial nerve supplies the posterior compartment of the leg, responsible for plantar flexion and toe flexion. Injury leads to loss of plantar flexion, weakened inversion, and sensory loss over the sole. Dorsiflexion is performed by the anterior compartment (deep peroneal nerve). The dorsum of the foot is supplied mainly by the superficial peroneal nerve.
Q1. Which of the following muscles is innervated by the tibial nerve?
a) Tibialis anterior
b) Gastrocnemius
c) Peroneus longus
d) Extensor digitorum longus
Explanation: The gastrocnemius muscle is part of the posterior compartment of the leg, innervated by the tibial nerve, and functions in plantar flexion. Tibialis anterior and extensor digitorum longus are supplied by the deep peroneal nerve. Peroneus longus is supplied by the superficial peroneal nerve.
Q2. Damage to the tibial nerve at the popliteal fossa results in loss of:
a) Dorsiflexion
b) Plantar flexion
c) Knee extension
d) Hip abduction
Explanation: Tibial nerve injury at the popliteal fossa causes loss of plantar flexion and toe flexion, as the posterior compartment muscles are denervated. Dorsiflexion is controlled by anterior compartment muscles. Knee extension is mediated by the femoral nerve, and hip abduction by the gluteal nerves.
Q3. Sensory loss in tibial nerve injury typically occurs over:
a) Dorsum of foot
b) Lateral leg
c) Sole of foot
d) Medial thigh
Explanation: The tibial nerve provides sensory innervation to the sole of the foot via the medial and lateral plantar nerves. The dorsum of the foot is innervated by the superficial peroneal nerve. Lateral leg sensation comes from the superficial peroneal and sural nerves; medial thigh is via femoral nerve branches.
Q4. Which reflex may be lost in tibial nerve injury?
a) Knee jerk
b) Ankle jerk
c) Biceps jerk
d) Plantar reflex
Explanation: The ankle jerk (Achilles tendon reflex) tests the S1-S2 roots via the tibial nerve. Tibial nerve injury abolishes this reflex. Knee jerk involves L2-L4 via femoral nerve, biceps jerk involves C5-C6 via musculocutaneous nerve, and plantar reflex tests corticospinal tract integrity.
Q5. The tibial nerve is a terminal branch of which nerve?
a) Femoral nerve
b) Obturator nerve
c) Sciatic nerve
d) Common peroneal nerve
Explanation: The sciatic nerve divides into the tibial and common peroneal nerves at the apex of the popliteal fossa. The tibial nerve continues downward to supply the posterior leg and sole of the foot. Femoral and obturator nerves are separate lumbar plexus branches.
Q6. In tarsal tunnel syndrome, which nerve is compressed?
a) Common peroneal nerve
b) Tibial nerve
c) Deep peroneal nerve
d) Sural nerve
Explanation: Tarsal tunnel syndrome is due to compression of the tibial nerve beneath the flexor retinaculum, causing pain, tingling, and numbness in the sole of the foot. The common and deep peroneal nerves are involved in anterior/lateral leg innervation; sural nerve supplies the posterolateral leg and lateral foot.
Q7. A patient with tibial nerve injury will have difficulty in:
a) Standing on toes
b) Standing on heels
c) Knee extension
d) Hip extension
Explanation: Standing on toes requires plantar flexion, which is mediated by the tibial nerve. Tibial nerve injury makes this action weak or impossible. Standing on heels requires dorsiflexion (deep peroneal nerve). Knee and hip extension are controlled by femoral and gluteal nerves respectively.
Q8. Which artery accompanies the tibial nerve in the posterior compartment of the leg?
a) Anterior tibial artery
b) Posterior tibial artery
c) Popliteal artery
d) Fibular artery
Explanation: The posterior tibial artery runs with the tibial nerve in the posterior compartment. Anterior tibial artery runs with deep peroneal nerve. Popliteal artery is above the split, and fibular artery is a branch of the posterior tibial artery.
Q9. Which muscle is spared in tibial nerve injury at the ankle?
a) Flexor hallucis longus
b) Flexor digitorum longus
c) Tibialis posterior
d) Gastrocnemius
Explanation: Injury at the ankle spares proximal muscles like gastrocnemius, tibialis posterior, and long toe flexors because they are innervated higher up. Only intrinsic foot muscles supplied by tibial nerve branches are affected.
Q10. Clinical feature of complete tibial nerve transection at popliteal fossa includes:
a) Foot drop
b) Clawing of toes
c) Loss of knee jerk
d) Loss of hip abduction
Explanation: Complete tibial nerve injury causes inability to plantar flex and invert foot, loss of sole sensation, absent ankle jerk, and clawing of toes due to intrinsic foot muscle paralysis. Foot drop is from common peroneal nerve injury. Knee jerk and hip abduction are unrelated to tibial nerve.
Cervical Esophagus: The uppermost part of the esophagus, extending from the cricopharyngeus to the thoracic inlet.
Vagus Nerve: Cranial nerve X, responsible for parasympathetic control of the heart, lungs, and digestive tract.
Recurrent Laryngeal Nerve: Branch of the vagus nerve that supplies motor function and sensation to the larynx and cervical esophagus.
Esophageal Innervation: Nerve supply that controls esophageal motility and sensation.
Parasympathetic Fibers: Nerve fibers that control involuntary functions like digestion and glandular activity.
Sympathetic Fibers: Nerve fibers involved in fight-or-flight responses, also affecting smooth muscle tone in the esophagus.
Cricopharyngeus Muscle: The upper esophageal sphincter controlling the entry of food into the esophagus.
Esophageal Motility Disorders: Conditions affecting the coordinated muscle contractions of the esophagus.
Leas Question 2012
Q1. (2012) Nerve supply of cervical esophagus?
a) Vagus
b) Left recurrent laryngeal nerve
c) Right recurrent laryngeal nerve
d) All of the above
Answer: d) All of the above
Explanation: The cervical esophagus receives motor innervation from both the right and left recurrent laryngeal nerves, which are branches of the vagus nerve. These nerves provide motor supply to striated muscles and sensory innervation to the mucosa. Sympathetic fibers from the cervical sympathetic chain also contribute, controlling muscle tone. Damage to these nerves can lead to dysphagia and aspiration.
Q2. Which muscle forms the upper esophageal sphincter?
a) Cricopharyngeus
b) Thyropharyngeus
c) Inferior constrictor
d) Stylopharyngeus
Answer: a) Cricopharyngeus
Explanation: The cricopharyngeus muscle is the principal component of the upper esophageal sphincter, regulating the passage of food into the cervical esophagus. It is innervated by the recurrent laryngeal nerve. Dysfunction may lead to Zenker’s diverticulum formation.
Q3. Injury to the left recurrent laryngeal nerve during thyroid surgery may cause?
a) Hoarseness
b) Dysphagia
c) Loss of gag reflex
d) Loss of taste sensation
Answer: a) Hoarseness
Explanation: The left recurrent laryngeal nerve supplies motor fibers to most intrinsic laryngeal muscles. Injury results in vocal cord paralysis, causing hoarseness, weak cough, and aspiration risk. This nerve also contributes to the cervical esophageal motor function.
Q4. Which nerve passes under the arch of the aorta before ascending to the larynx?
a) Left recurrent laryngeal nerve
b) Right recurrent laryngeal nerve
c) Vagus nerve
d) Glossopharyngeal nerve
Answer: a) Left recurrent laryngeal nerve
Explanation: The left recurrent laryngeal nerve loops under the aortic arch, while the right loops under the subclavian artery. This anatomical difference explains why left-sided nerve palsy may occur in thoracic diseases affecting the aorta or mediastinum.
Q5. Sympathetic innervation of the cervical esophagus arises from?
a) Stellate ganglion
b) Cervical sympathetic chain
c) Thoracic sympathetic chain
d) Both a and b
Answer: d) Both a and b
Explanation: Sympathetic fibers from the cervical sympathetic chain, including the stellate ganglion, provide vasomotor and smooth muscle tone control to the cervical esophagus. These fibers complement parasympathetic vagal input for coordinated swallowing.
Q6. Which cranial nerve is responsible for parasympathetic innervation of the cervical esophagus?
a) Glossopharyngeal
b) Vagus
c) Accessory
d) Hypoglossal
Answer: b) Vagus
Explanation: The vagus nerve (cranial nerve X) carries parasympathetic fibers to the esophagus, facilitating peristalsis and glandular secretions. Recurrent laryngeal branches of the vagus provide the direct motor supply to the cervical portion.
Q7. A tumor compressing the left recurrent laryngeal nerve can present with all EXCEPT?
a) Stridor
b) Hoarseness
c) Dysphagia
d) Hyperacusis
Answer: d) Hyperacusis
Explanation: Hyperacusis is due to facial nerve (CN VII) involvement. Compression of the left recurrent laryngeal nerve by tumors such as lung carcinoma or mediastinal masses leads to hoarseness, stridor, and dysphagia but not auditory hypersensitivity.
Q8. Clinical sign most suggestive of bilateral recurrent laryngeal nerve injury?
a) Aphonia
b) Inspiratory stridor
c) Dysphagia
d) Nasal regurgitation
Answer: b) Inspiratory stridor
Explanation: Bilateral injury to recurrent laryngeal nerves causes vocal cord adduction, narrowing the airway and producing inspiratory stridor. This is a surgical emergency often seen after thyroidectomy complications.
Q9. The cervical esophagus transitions from striated to smooth muscle at approximately what vertebral level?
a) C4
b) C6
c) T1
d) T4
Answer: b) C6
Explanation: At the C6 vertebral level, the pharyngoesophageal junction marks the start of the esophagus. The upper part contains striated muscle fibers, gradually transitioning to smooth muscle in the thoracic portion.
Q10. Which nerve is most vulnerable during anterior cervical spine surgery?
a) Hypoglossal
b) Recurrent laryngeal
c) Vagus
d) Glossopharyngeal
Answer: b) Recurrent laryngeal
Explanation: Anterior cervical spine approaches risk injury to the recurrent laryngeal nerve due to its proximity to the tracheoesophageal groove. Injury can lead to hoarseness, aspiration, and swallowing difficulties.
Q11. The esophageal plexus is primarily formed by?
a) Glossopharyngeal and hypoglossal
b) Vagus and sympathetic fibers
c) Facial and trigeminal
d) Phrenic and accessory
Answer: b) Vagus and sympathetic fibers
Explanation: The esophageal plexus is formed by branches from the vagus nerve and sympathetic chain, integrating parasympathetic and sympathetic control of motility and glandular secretions along the esophagus.