Chapter: Sensory Physiology; Topic: Special Senses; Subtopic: Taste Sensation (Gustation)
Keyword Definitions:
• Umami: One of the five basic taste sensations, producing a savory flavor mainly due to amino acids like glutamate.
• Taste Buds: Specialized sensory structures containing gustatory cells that detect different taste modalities.
• Gustatory Pathway: Neural pathway transmitting taste sensations via cranial nerves VII, IX, and X to the gustatory cortex.
• Glutamic Acid: An amino acid that activates umami receptors, enhancing the flavor of protein-rich foods.
Lead Question - 2014
Umami taste is evoked by ?
a) Glucose
b) Glutamic acid
c) Quinine
d) Sodium chloride
Answer & Explanation: The correct answer is b) Glutamic acid. The umami taste is produced by monosodium glutamate (MSG) and certain amino acids such as glutamic acid. It represents the savory taste associated with protein-rich foods. Umami receptors (mGluR4 and T1R1/T1R3) detect these compounds and transmit signals via the glossopharyngeal and facial nerves to the gustatory cortex.
1) Which papillae of the tongue contain the maximum number of taste buds?
a) Fungiform
b) Vallate
c) Foliate
d) Filiform
Answer & Explanation: The correct answer is b) Vallate. Vallate papillae are large structures located in a V-shape at the posterior tongue. Each papilla contains hundreds of taste buds and plays a vital role in detecting bitter and umami tastes. Filiform papillae, in contrast, are numerous but non-gustatory, serving mainly mechanical functions during chewing and swallowing.
2) Sweet taste is mediated through which receptor mechanism?
a) Direct ion channel
b) G-protein coupled receptor
c) Ligand-gated ion channel
d) Voltage-gated sodium channel
Answer & Explanation: The correct answer is b) G-protein coupled receptor. Sweet taste perception involves G-protein coupled receptors (T1R2 and T1R3). When sugars or artificial sweeteners bind, second messenger pathways activate gustatory nerves. This mechanism differs from salty or sour tastes, which rely on direct ion channels for sodium and hydrogen ions, respectively.
3) Which taste sensation is most sensitive to low threshold levels?
a) Sweet
b) Bitter
c) Salty
d) Umami
Answer & Explanation: The correct answer is b) Bitter. Bitter taste receptors are highly sensitive, enabling the detection of potentially toxic alkaloids at minimal concentrations. This protective mechanism triggers aversive responses, reducing ingestion of harmful substances. Bitter taste receptors (T2Rs) are predominantly located in the posterior tongue within the vallate papillae.
4) A patient with glossopharyngeal nerve injury would lose taste sensation mainly from:
a) Anterior two-thirds of the tongue
b) Posterior one-third of the tongue
c) Tip of the tongue
d) Palate
Answer & Explanation: The correct answer is b) Posterior one-third of the tongue. The glossopharyngeal nerve (cranial nerve IX) supplies taste fibers to the posterior one-third of the tongue. Its damage leads to loss of bitter and umami taste perception in that region. The chorda tympani branch of the facial nerve carries taste from the anterior tongue.
5) Which ion is primarily responsible for the perception of salty taste?
a) Sodium ion
b) Potassium ion
c) Calcium ion
d) Chloride ion
Answer & Explanation: The correct answer is a) Sodium ion. Salty taste is mainly due to the entry of sodium ions through epithelial sodium channels (ENaCs) in taste cells. This depolarizes the gustatory membrane, leading to neurotransmitter release. Thus, sodium concentration directly correlates with the intensity of perceived saltiness in foods.
6) A 40-year-old man complains of complete loss of taste following Bell’s palsy. The likely site of lesion is:
a) Facial nerve proximal to chorda tympani
b) Vagus nerve
c) Glossopharyngeal nerve
d) Hypoglossal nerve
Answer & Explanation: The correct answer is a) Facial nerve proximal to chorda tympani. The chorda tympani branch of the facial nerve conveys taste from the anterior two-thirds of the tongue. Damage near its origin leads to ageusia (loss of taste). Bell’s palsy involves facial nerve paralysis, which may also impair salivation and lacrimation functions.
7) Which cranial nerves are involved in carrying taste sensations?
a) VII, IX, X
b) V, VII, IX
c) IX, X, XI
d) V, IX, XII
Answer & Explanation: The correct answer is a) VII, IX, X. The facial nerve (VII) carries taste from the anterior tongue, the glossopharyngeal (IX) from the posterior tongue, and the vagus (X) from the epiglottis and pharynx. These fibers converge at the nucleus tractus solitarius before projecting to the gustatory cortex for taste perception.
8) In umami taste perception, which receptor pair is activated?
a) T1R1 and T1R3
b) T2R1 and T2R2
c) T1R2 and T1R3
d) T1R1 and T2R3
Answer & Explanation: The correct answer is a) T1R1 and T1R3. These metabotropic receptors are sensitive to amino acids like glutamate. When activated, they trigger G-protein (gustducin)-mediated pathways leading to neurotransmitter release. This signaling mechanism forms the molecular basis for umami taste perception, especially from protein-rich foods such as meat and cheese.
9) A patient taking cisplatin chemotherapy develops loss of taste. The likely cause is:
a) Damage to taste buds
b) Increased salivary secretion
c) Enhanced nerve conduction
d) Nasal congestion
Answer & Explanation: The correct answer is a) Damage to taste buds. Cisplatin and other chemotherapeutic drugs cause cytotoxic injury to rapidly regenerating taste bud cells, leading to dysgeusia or ageusia. Recovery occurs after regeneration of gustatory cells. The effect highlights the dependence of taste function on healthy epithelial renewal in the oral cavity.
10) The central taste pathway terminates in which cortical region?
a) Occipital cortex
b) Insular cortex
c) Temporal cortex
d) Parietal association cortex
Answer & Explanation: The correct answer is b) Insular cortex. The gustatory pathway ends in the insula and frontal operculum. These regions integrate taste with olfactory and somatosensory inputs to form flavor perception. Lesions here impair the conscious recognition of taste, even when peripheral taste receptor function remains intact.
Chapter: Central Nervous System; Topic: Limbic System; Subtopic: Reward and Motivation Pathways
Keyword Definitions:
• Reward Center: A group of brain structures that produce pleasure or motivation when stimulated, mainly located in the hypothalamus and limbic system.
• Hypothalamus: A diencephalic structure regulating hunger, thirst, emotion, and endocrine activity.
• Limbic System: A set of interconnected structures involved in emotion, memory, and motivation including hippocampus, amygdala, and cingulate gyrus.
• Dopamine Pathway: Neurotransmitter system responsible for pleasure, motivation, and reinforcement learning.
Lead Question - 2014
Reward center is located in ?
a) Cerebellum
b) Amygdala
c) Hippocampus
d) Hypothalamus
Answer & Explanation: The correct answer is d) Hypothalamus. The reward center, primarily located in the lateral hypothalamus and medial forebrain bundle, produces sensations of pleasure and motivation when stimulated. This dopaminergic pathway connects to the nucleus accumbens and ventral tegmental area (VTA). It plays a major role in reinforcement behavior, addiction, and learning mechanisms.
1) The neurotransmitter most closely associated with the reward system is:
a) Acetylcholine
b) Dopamine
c) Serotonin
d) GABA
Answer & Explanation: The correct answer is b) Dopamine. Dopamine released from the ventral tegmental area (VTA) to the nucleus accumbens reinforces rewarding stimuli. It is crucial in motivation, addiction, and reinforcement learning. Drugs like cocaine and amphetamines increase dopamine levels, leading to strong activation of the brain’s reward system and reinforcing addictive behavior.
2) Which structure forms a part of the mesolimbic dopamine pathway?
a) Substantia nigra
b) Nucleus accumbens
c) Locus coeruleus
d) Red nucleus
Answer & Explanation: The correct answer is b) Nucleus accumbens. The mesolimbic pathway originates in the ventral tegmental area (VTA) and projects to the nucleus accumbens, amygdala, and prefrontal cortex. It mediates reward, pleasure, and addiction-related behavior. Overstimulation of this circuit contributes to substance dependence and motivational disorders.
3) Which brain structure is primarily responsible for fear and aggression?
a) Amygdala
b) Hippocampus
c) Hypothalamus
d) Pons
Answer & Explanation: The correct answer is a) Amygdala. The amygdala, part of the limbic system, regulates emotional responses such as fear, aggression, and anxiety. It works with the hypothalamus and prefrontal cortex to coordinate autonomic and behavioral reactions. Lesions reduce fear responses, whereas hyperactivity contributes to anxiety and panic disorders.
4) A patient with bilateral damage to the hippocampus is most likely to have:
a) Loss of balance
b) Memory impairment
c) Speech difficulty
d) Visual field defect
Answer & Explanation: The correct answer is b) Memory impairment. The hippocampus plays a central role in converting short-term memories into long-term storage. Bilateral damage, as seen in conditions like Alzheimer’s disease or hypoxic injury, causes anterograde amnesia. However, previously stored memories may remain intact, highlighting its selective role in memory consolidation.
5) Which of the following best describes the function of the limbic system?
a) Coordination of voluntary movements
b) Regulation of emotion and behavior
c) Control of reflexes
d) Maintenance of balance
Answer & Explanation: The correct answer is b) Regulation of emotion and behavior. The limbic system integrates emotional experiences with behavior, motivation, and memory. Structures such as the amygdala, hippocampus, and hypothalamus work together to influence emotional learning, decision-making, and social responses through neurotransmitters like dopamine and serotonin.
6) A 28-year-old man experiences euphoria and pleasure after drug use. Which neural pathway is primarily activated?
a) Mesocortical pathway
b) Mesolimbic pathway
c) Nigrostriatal pathway
d) Tuberoinfundibular pathway
Answer & Explanation: The correct answer is b) Mesolimbic pathway. This dopaminergic pathway originates in the ventral tegmental area (VTA) and projects to the nucleus accumbens. Activation produces sensations of pleasure and reinforcement. Chronic overstimulation by addictive substances leads to tolerance and craving through neural adaptation mechanisms.
7) Which part of the hypothalamus is associated with satiety?
a) Lateral hypothalamus
b) Ventromedial hypothalamus
c) Posterior hypothalamus
d) Anterior hypothalamus
Answer & Explanation: The correct answer is b) Ventromedial hypothalamus. The ventromedial nucleus acts as the satiety center, inhibiting feeding behavior. Lesions cause hyperphagia and obesity, whereas stimulation reduces appetite. The lateral hypothalamus, in contrast, functions as the feeding center and is involved in reward-driven eating behavior.
8) Which neurotransmitter imbalance is implicated in depression?
a) Increased dopamine
b) Decreased serotonin and norepinephrine
c) Increased GABA
d) Increased glutamate
Answer & Explanation: The correct answer is b) Decreased serotonin and norepinephrine. Depression is associated with reduced levels of serotonin, norepinephrine, and dopamine. Antidepressants like SSRIs increase serotonin levels in synaptic clefts, improving mood regulation. These monoamines are integral to limbic system circuits controlling emotion, sleep, and motivation.
9) A 45-year-old man with Parkinson’s disease has reduced activity in which dopaminergic pathway?
a) Mesolimbic
b) Mesocortical
c) Nigrostriatal
d) Tuberoinfundibular
Answer & Explanation: The correct answer is c) Nigrostriatal. The nigrostriatal pathway connects the substantia nigra to the striatum. Degeneration of dopaminergic neurons in this pathway causes motor symptoms of Parkinson’s disease, including tremor, rigidity, and bradykinesia. Dopamine replacement therapy helps restore function and reduce symptoms.
10) A 50-year-old woman with temporal lobe epilepsy experiences intense emotional auras before seizures. Which structure is involved?
a) Amygdala
b) Thalamus
c) Hypothalamus
d) Medulla
Answer & Explanation: The correct answer is a) Amygdala. The amygdala, located in the temporal lobe, is a major site of epileptic discharges causing emotional experiences such as fear or déjà vu. It connects with the hippocampus and hypothalamus, linking emotional processing to autonomic responses during seizure activity.
Chapter: Central Nervous System; Topic: Motor Systems; Subtopic: Extrapyramidal vs Pyramidal Tracts
Keyword Definitions:
• Extrapyramidal Tracts: Motor pathways that control involuntary movements, posture, and muscle tone, not directly via the corticospinal (pyramidal) tract.
• Pyramidal Tract: Direct motor pathway (corticospinal and corticobulbar tracts) responsible for voluntary fine movements.
• Reticulospinal Tract: Extrapyramidal pathway modulating voluntary and reflex motor activity and muscle tone.
• Rubrospinal Tract: Extrapyramidal tract originating in the red nucleus; facilitates flexor muscles and inhibits extensors.
• Tectospinal Tract: Extrapyramidal tract mediating reflex postural movements in response to visual and auditory stimuli.
Lead Question - 2014
Which is not an extrapyramidal tract ?
a) Reticulospinal tract
b) Rubrospinal tract
c) Corticospinal tract
d) Tectospinal tract
Answer & Explanation: The correct answer is c) Corticospinal tract. The corticospinal tract is a pyramidal tract that directly connects the cerebral cortex to spinal motor neurons to control voluntary fine movements. Extrapyramidal tracts, including reticulospinal, rubrospinal, and tectospinal tracts, regulate involuntary movements, posture, and muscle tone indirectly through brainstem motor centers. Damage to extrapyramidal pathways leads to movement disorders such as rigidity, tremor, and abnormal posturing, while corticospinal tract lesions cause weakness and spasticity.
1) Which extrapyramidal tract primarily facilitates flexor muscles of the upper limb?
a) Reticulospinal tract
b) Rubrospinal tract
c) Vestibulospinal tract
d) Tectospinal tract
Answer & Explanation: The correct answer is b) Rubrospinal tract. Originating in the red nucleus, the rubrospinal tract facilitates upper limb flexors and inhibits extensors, contributing to postural control and fine motor coordination. Lesions produce weakness in flexor muscles, affecting voluntary limb movements, while gross motor functions are preserved through corticospinal pathways and other extrapyramidal tracts.
2) Which extrapyramidal tract originates from the pontine and medullary reticular formation?
a) Reticulospinal tract
b) Rubrospinal tract
c) Corticospinal tract
d) Vestibulospinal tract
Answer & Explanation: The correct answer is a) Reticulospinal tract. This tract originates in the pontine and medullary reticular formation and projects to spinal interneurons. It modulates voluntary movement, reflex activity, and muscle tone, facilitating automatic posture and locomotion. Damage leads to abnormal tone, spasticity, and impaired postural adjustments.
3) Which tract is responsible for reflex postural movements in response to visual stimuli?
a) Rubrospinal tract
b) Reticulospinal tract
c) Tectospinal tract
d) Corticospinal tract
Answer & Explanation: The correct answer is c) Tectospinal tract. Originating from the superior colliculus in the midbrain, the tectospinal tract mediates reflex head and neck movements toward visual and auditory stimuli. It coordinates posture with sensory input, contributing to orientation and protective reflexes, whereas pyramidal tracts are involved in voluntary motor control.
4) Lesion of the corticospinal tract typically results in:
a) Rigidity
b) Tremor
c) Spastic paralysis
d) Abnormal posture
Answer & Explanation: The correct answer is c) Spastic paralysis. The corticospinal (pyramidal) tract directly transmits motor signals from the cortex to spinal motor neurons. Lesions lead to spasticity, hyperreflexia, and weakness of voluntary movements, mainly affecting fine motor control. Extrapyramidal lesions, by contrast, produce rigidity, tremor, and abnormal postural changes without direct weakness.
5) The vestibulospinal tract primarily influences:
a) Fine finger movements
b) Axial and proximal limb muscles for posture
c) Reflexes in cranial nerves
d) Sensory perception
Answer & Explanation: The correct answer is b) Axial and proximal limb muscles for posture. The vestibulospinal tract originates in vestibular nuclei and controls balance and posture by influencing axial and proximal limb muscles. It is part of the extrapyramidal system and works in coordination with other tracts to maintain upright stance and compensate for perturbations.
6) Which tract is primarily responsible for facilitating voluntary fine movements?
a) Corticospinal tract
b) Rubrospinal tract
c) Reticulospinal tract
d) Tectospinal tract
Answer & Explanation: The correct answer is a) Corticospinal tract. The corticospinal tract is a pyramidal pathway critical for precise voluntary movements, especially of distal muscles in the hands and fingers. Extrapyramidal tracts support gross movements, posture, and reflex modulation, but fine dexterity depends primarily on corticospinal projections.
7) A patient exhibits rigidity, tremor, and abnormal posture with preserved voluntary strength. Which system is likely affected?
a) Pyramidal system
b) Extrapyramidal system
c) Cerebellar system
d) Sensory system
Answer & Explanation: The correct answer is b) Extrapyramidal system. Extrapyramidal lesions impair involuntary movement control, leading to rigidity, tremor, bradykinesia, and abnormal posture. Voluntary strength remains relatively preserved because the pyramidal tract (corticospinal) is intact. Parkinson’s disease is a classical example of extrapyramidal dysfunction affecting motor control indirectly.
8) Which tract is not involved in involuntary postural adjustments?
a) Reticulospinal tract
b) Rubrospinal tract
c) Corticospinal tract
d) Vestibulospinal tract
Answer & Explanation: The correct answer is c) Corticospinal tract. While corticospinal fibers mediate voluntary movement, extrapyramidal tracts like reticulospinal, rubrospinal, and vestibulospinal tracts regulate involuntary adjustments, muscle tone, and posture. Damage to extrapyramidal tracts impairs balance and reflexive movements but spares voluntary motor power.
9) Which tract primarily projects from the red nucleus in the midbrain?
a) Rubrospinal tract
b) Reticulospinal tract
c) Corticospinal tract
d) Vestibulospinal tract
Answer & Explanation: The correct answer is a) Rubrospinal tract. The rubrospinal tract originates from the red nucleus and modulates flexor muscle activity while inhibiting extensors, mainly affecting upper limb movements. It complements the corticospinal tract and is a key component of the extrapyramidal motor system.
10) Which statement differentiates pyramidal from extrapyramidal tracts?
a) Pyramidal controls involuntary movements; extrapyramidal controls voluntary fine movements
b) Pyramidal originates in brainstem; extrapyramidal originates in cortex
c) Pyramidal directly connects cortex to motor neurons; extrapyramidal modulates movement indirectly
d) Pyramidal is part of basal ganglia; extrapyramidal is part of cortex
Answer & Explanation: The correct answer is c) Pyramidal directly connects cortex to motor neurons; extrapyramidal modulates movement indirectly. The pyramidal system (corticospinal and corticobulbar tracts) allows direct voluntary control, especially of distal muscles. Extrapyramidal tracts, including rubrospinal, reticulospinal, vestibulospinal, and tectospinal, influence posture, tone, and reflexive movements indirectly through brainstem and spinal interneurons. Damage to either system produces distinct motor deficits.
Chapter: Central Nervous System; Topic: Motor Systems; Subtopic: Posture and Balance Control
Keyword Definitions:
• Basal Ganglia: Group of subcortical nuclei regulating voluntary motor control, procedural learning, routine behaviors, and posture.
• Cerebellum: Brain structure controlling coordination, precision, balance, and posture of voluntary movements.
• Hypothalamus: Brain region controlling autonomic functions, endocrine activity, and homeostasis.
• Amygdala: Limbic system structure involved in emotion processing and fear responses.
• Posture: The position in which the body is held while standing, walking, or resting.
Lead Question - 2014
While walking or standing, posture is maintained by ?
a) Basal ganglia
b) Hypothalamus
c) Cerebellum
d) Amygdala
Answer & Explanation: The correct answer is c) Cerebellum. The cerebellum integrates sensory inputs from vestibular, visual, and proprioceptive systems to fine-tune muscle activity for balance and posture. It ensures smooth coordination during standing and walking, preventing falls. Basal ganglia regulate initiation and amplitude of movements, but maintenance of upright posture and real-time adjustments primarily depend on cerebellar circuits. Damage to the cerebellum results in ataxia, unsteady gait, and difficulty maintaining posture. Hypothalamus and amygdala do not directly control posture but are involved in homeostasis and emotional processing, respectively.
1) Lesion in cerebellum results in which of the following?
a) Rigidity
b) Ataxia
c) Tremor only
d) Hemiplegia
Answer & Explanation: The correct answer is b) Ataxia. Cerebellar lesions disrupt coordination and balance, causing ataxia, unsteady gait, dysmetria, and inability to maintain posture. Muscle strength may remain normal, differentiating it from pyramidal tract lesions. Both medial and lateral cerebellar damage can affect axial control and limb coordination, leading to pronounced difficulty in standing or walking.
2) Which part of the cerebellum primarily controls posture and balance?
a) Lateral hemispheres
b) Vermis
c) Flocculonodular lobe
d) Dentate nucleus
Answer & Explanation: The correct answer is b) Vermis. The vermis receives input from the vestibular system and proprioceptors to control axial muscles and maintain posture. Lesions here cause truncal ataxia and imbalance, affecting standing and walking. The flocculonodular lobe also contributes to balance via vestibular connections, while lateral hemispheres fine-tune limb coordination for voluntary movements.
3) Which sensory system provides feedback for posture maintenance?
a) Visual
b) Vestibular
c) Proprioceptive
d) All of the above
Answer & Explanation: The correct answer is d) All of the above. Posture control integrates visual, vestibular, and proprioceptive inputs. Visual system detects environmental orientation, vestibular system senses head position and motion, and proprioceptors monitor muscle and joint status. The cerebellum processes these signals to maintain balance during standing and walking.
4) Which pathway is critical for postural reflexes?
a) Corticospinal tract
b) Vestibulospinal tract
c) Spinothalamic tract
d) Optic tract
Answer & Explanation: The correct answer is b) Vestibulospinal tract. The vestibulospinal tract originates in vestibular nuclei and projects to spinal interneurons controlling axial and proximal limb muscles. It mediates postural reflexes in response to changes in head position, working with cerebellar input to maintain stability during walking and standing.
5) Damage to basal ganglia affects posture primarily by:
a) Causing rigidity and bradykinesia
b) Causing ataxia
c) Causing tremor only
d) Impairing sensory feedback
Answer & Explanation: The correct answer is a) Causing rigidity and bradykinesia. Basal ganglia lesions, as in Parkinson’s disease, lead to rigidity, decreased movement amplitude, and postural instability. While the cerebellum adjusts balance dynamically, basal ganglia lesions indirectly impair posture by limiting smooth initiation and scaling of movements.
6) Which cerebellar disorder leads to broad-based, unsteady gait?
a) Spinocerebellar ataxia
b) Stroke in motor cortex
c) Parkinson’s disease
d) Amyotrophic lateral sclerosis
Answer & Explanation: The correct answer is a) Spinocerebellar ataxia. Degenerative cerebellar diseases, such as spinocerebellar ataxia, impair coordination and trunk stability, producing a broad-based, staggering gait. Patients often sway while standing, with difficulty maintaining balance during ambulation, highlighting the cerebellum’s key role in posture maintenance.
7) Which lobe of the cerebellum is primarily connected to vestibular nuclei?
a) Anterior lobe
b) Posterior lobe
c) Flocculonodular lobe
d) Lateral hemisphere
Answer & Explanation: The correct answer is c) Flocculonodular lobe. The flocculonodular lobe receives direct vestibular input to coordinate eye movements and balance. Lesions here result in truncal ataxia, impaired standing, and tendency to fall, emphasizing its role in posture and equilibrium.
8) Postural adjustments during walking are integrated mainly by:
a) Hypothalamus
b) Amygdala
c) Cerebellum and brainstem nuclei
d) Spinal cord only
Answer & Explanation: The correct answer is c) Cerebellum and brainstem nuclei. The cerebellum processes sensory input from vestibular, proprioceptive, and visual systems, while brainstem nuclei like vestibular and reticular formations implement rapid postural reflexes. Together, they ensure dynamic balance during locomotion, preventing falls.
9) Which clinical sign indicates cerebellar involvement affecting posture?
a) Positive Romberg sign
b) Hemiplegia
c) Hyperreflexia
d) Spasticity
Answer & Explanation: The correct answer is a) Positive Romberg sign. A positive Romberg test, showing instability when eyes are closed, reflects impaired integration of proprioceptive and cerebellar signals needed for posture maintenance. Cerebellar lesions or sensory deficits compromise standing balance, confirming involvement in postural control.
10) During standing, rapid corrective movements to prevent falling are controlled primarily by:
a) Corticospinal tract
b) Vestibulospinal and reticulospinal tracts
c) Spinothalamic tract
d) Hypothalamospinal tract
Answer & Explanation: The correct answer is b) Vestibulospinal and reticulospinal tracts. These extrapyramidal tracts, guided by cerebellar input, activate axial and proximal limb muscles to maintain posture. Vestibulospinal tract responds to head movement, while reticulospinal tract adjusts tone and reflexes. Damage to these pathways causes instability and postural imbalance.
Chapter: Nervous System; Topic: Peripheral Nervous System; Subtopic: Myelination
Keyword Definitions:
• Myelination: Process of forming a myelin sheath around axons to increase conduction velocity of nerve impulses.
• Peripheral Nervous System (PNS): Part of the nervous system outside brain and spinal cord, including cranial and spinal nerves.
• Schwann cells: Glial cells in PNS responsible for forming myelin sheaths around peripheral axons.
• Oligodendrocytes: CNS glial cells that myelinate multiple axons in the brain and spinal cord.
• Astrocytes: Star-shaped CNS glial cells supporting neurons, regulating extracellular environment, but not myelinating axons.
• Ependymal cells: CNS glial cells lining ventricles, involved in cerebrospinal fluid production, not myelination.
Lead Question - 2014
Myelination in peripheral nervous system is done by ?
a) Astrocytes
b) Oligodendrocytes
c) Ependymal cells
d) Schwann cells
Answer & Explanation: The correct answer is d) Schwann cells. Schwann cells are the primary glial cells of the PNS responsible for myelinating peripheral nerves. Each Schwann cell wraps around a single axon segment, forming a myelin sheath that increases conduction speed of action potentials. Unlike oligodendrocytes in the CNS, which can myelinate multiple axons, Schwann cells provide one-to-one myelination. Damage to Schwann cells, as in peripheral neuropathies, leads to slowed nerve conduction, muscle weakness, and sensory deficits. Astrocytes and ependymal cells are CNS glia and do not myelinate axons.
1) Which CNS cell myelinates multiple axons?
a) Schwann cells
b) Oligodendrocytes
c) Astrocytes
d) Microglia
Answer & Explanation: The correct answer is b) Oligodendrocytes. Oligodendrocytes myelinate multiple CNS axons simultaneously, increasing conduction speed. In contrast, Schwann cells myelinate individual PNS axons. Astrocytes provide support and maintain extracellular environment, while microglia act as immune cells in CNS.
2) Which disease involves demyelination in PNS?
a) Multiple sclerosis
b) Guillain-Barré syndrome
c) Alzheimer’s disease
d) Parkinson’s disease
Answer & Explanation: The correct answer is b) Guillain-Barré syndrome. This autoimmune disorder targets Schwann cells, causing demyelination of peripheral nerves, leading to muscle weakness, paresthesia, and areflexia. Multiple sclerosis affects CNS myelin formed by oligodendrocytes, while Alzheimer’s and Parkinson’s are neurodegenerative but not primarily demyelinating.
3) Node of Ranvier is associated with:
a) Schwann cells
b) Oligodendrocytes
c) Astrocytes
d) Microglia
Answer & Explanation: The correct answer is a) Schwann cells. Nodes of Ranvier are gaps between Schwann cell myelin segments along PNS axons, allowing saltatory conduction. These nodes facilitate rapid action potential propagation. CNS nodes are similarly associated with oligodendrocyte myelin.
4) Which PNS glial cell also aids in axon regeneration?
a) Oligodendrocytes
b) Schwann cells
c) Astrocytes
d) Ependymal cells
Answer & Explanation: The correct answer is b) Schwann cells. Schwann cells produce growth factors and form bands of Büngner to guide regenerating axons after peripheral nerve injury. CNS oligodendrocytes inhibit regeneration, while astrocytes and ependymal cells are CNS supportive cells without regenerative function.
5) Which statement is true?
a) Schwann cells myelinate CNS
b) Oligodendrocytes myelinate PNS
c) Schwann cells myelinate PNS
d) Astrocytes myelinate both CNS and PNS
Answer & Explanation: The correct answer is c) Schwann cells myelinate PNS. Schwann cells wrap single axons in the PNS, whereas oligodendrocytes myelinate multiple CNS axons. Astrocytes do not form myelin; they maintain extracellular ionic balance and support neurons.
6) Which protein is major in PNS myelin?
a) Myelin basic protein (MBP)
b) Proteolipid protein (PLP)
c) Myelin protein zero (P0)
d) Neurofilament
Answer & Explanation: The correct answer is c) Myelin protein zero (P0). P0 is a structural glycoprotein in Schwann cell myelin, essential for compaction and stability. MBP and PLP are predominant in CNS myelin, while neurofilaments form the axonal cytoskeleton.
7) Peripheral neuropathy due to diabetes affects:
a) Oligodendrocytes
b) Schwann cells
c) Astrocytes
d) Microglia
Answer & Explanation: The correct answer is b) Schwann cells. Chronic hyperglycemia damages Schwann cells, leading to demyelination and impaired nerve conduction. Symptoms include distal sensory loss, weakness, and slowed reflexes. CNS glial cells remain largely unaffected.
8) Which factor stimulates Schwann cell myelination?
a) High neuronal activity
b) Low axonal diameter
c) Absence of laminin
d) Astrocytic signaling
Answer & Explanation: The correct answer is a) High neuronal activity. Active axons induce Schwann cells to myelinate via electrical activity and neuregulin signaling. Large-diameter axons are preferentially myelinated. Laminin supports but absence inhibits myelination; astrocytes are CNS glia.
9) Which PNS structure is unmyelinated but surrounded by Schwann cells?
a) Large motor axons
b) Small pain fibers
c) Oligodendrocyte processes
d) Corticospinal axons
Answer & Explanation: The correct answer is b) Small pain fibers. Unmyelinated C fibers are enveloped by non-myelinating Schwann cells forming Remak bundles, allowing support and trophic function without fast conduction. Large motor axons are myelinated for rapid transmission.
10) In PNS regeneration, Schwann cells:
a) Inhibit axon growth
b) Form myelin only
c) Guide regenerating axons
d) Replace oligodendrocytes
Answer & Explanation: The correct answer is c) Guide regenerating axons. After injury, Schwann cells proliferate, form bands of Büngner, and secrete neurotrophic factors, facilitating axon regrowth. CNS oligodendrocytes cannot guide regeneration, leading to limited CNS repair.
Chapter: Nervous System; Topic: Cerebral Cortex; Subtopic: Sensory Perception
Keyword Definitions:
• Sensory perception: The process by which the brain receives and interprets sensory input from the environment via specialized receptors.
• Brodmann's areas: Cytoarchitectonic regions of the cerebral cortex defined by Korbinian Brodmann, each with specific functional roles.
• Primary somatosensory cortex: Located in postcentral gyrus (areas 3,1,2), responsible for tactile, proprioceptive, and pressure sensation.
• Motor cortex: Areas 4 and 6, responsible for voluntary movement.
• Broca's area: Areas 44 and 45, involved in speech production.
• Primary auditory cortex: Areas 41 and 42, responsible for hearing perception.
Lead Question - 2014
Sensory perception involves Brodmann's area ?
a) 3, 1, 2
b) 4, 6
c) 44, 45
d) 41, 42
Answer & Explanation: The correct answer is a) 3, 1, 2. Brodmann areas 3, 1, and 2 comprise the primary somatosensory cortex located in the postcentral gyrus of the parietal lobe. These areas receive input from the thalamus corresponding to tactile, pressure, pain, and proprioceptive signals from the contralateral side of the body. Damage to these areas results in sensory deficits such as numbness or loss of tactile discrimination. Areas 4 and 6 are motor cortices, 44 and 45 are Broca’s speech areas, and 41 and 42 are primary auditory areas involved in hearing perception.
1) Lesion in Brodmann areas 3,1,2 causes:
a) Hemiplegia
b) Loss of tactile sensation
c) Aphasia
d) Cortical deafness
Answer & Explanation: The correct answer is b) Loss of tactile sensation. Lesions in areas 3,1,2 disrupt processing of somatosensory information, causing contralateral deficits in touch, vibration, proprioception, and stereognosis, while motor and auditory functions remain unaffected.
2) Primary motor cortex corresponds to which Brodmann area?
a) 3,1,2
b) 4
c) 6
d) 41,42
Answer & Explanation: The correct answer is b) 4. Area 4, located in the precentral gyrus, is the primary motor cortex responsible for voluntary movement initiation. Area 6 is premotor/supplementary motor cortex aiding planning, while 3,1,2 is sensory and 41,42 is auditory.
3) Broca’s area is involved in:
a) Sensory perception
b) Motor planning
c) Speech production
d) Hearing
Answer & Explanation: The correct answer is c) Speech production. Broca’s area (44,45) located in the inferior frontal gyrus of the dominant hemisphere coordinates speech articulation. Lesions cause expressive aphasia, while sensory perception remains intact.
4) Lesion in area 41,42 causes:
a) Cortical deafness
b) Hemiplegia
c) Apraxia
d) Agnosia
Answer & Explanation: The correct answer is a) Cortical deafness. Areas 41 and 42 constitute the primary auditory cortex in the superior temporal gyrus. Damage here results in inability to perceive sound despite intact peripheral auditory apparatus.
5) Somatosensory association cortex corresponds to:
a) 5,7
b) 4
c) 44,45
d) 41,42
Answer & Explanation: The correct answer is a) 5,7. Areas 5 and 7 integrate somatosensory information to recognize object size, shape, and spatial relations, facilitating perception and motor planning.
6) Lesion in postcentral gyrus may lead to:
a) Contralateral hemiplegia
b) Contralateral sensory loss
c) Broca’s aphasia
d) Cortical blindness
Answer & Explanation: The correct answer is b) Contralateral sensory loss. Postcentral gyrus houses primary somatosensory cortex (3,1,2). Lesion affects contralateral tactile, proprioceptive, and vibratory sensations without affecting motor function.
7) Primary gustatory cortex is located in:
a) Insula and frontal operculum
b) Postcentral gyrus
c) Precentral gyrus
d) Superior temporal gyrus
Answer & Explanation: The correct answer is a) Insula and frontal operculum. Gustatory cortex processes taste, while primary somatosensory cortex (3,1,2) processes touch and proprioception.
8) Damage to area 3 alone may cause:
a) Loss of vibration sense
b) Loss of voluntary movement
c) Aphasia
d) Cortical deafness
Answer & Explanation: The correct answer is a) Loss of vibration sense. Area 3 receives direct thalamic input, critical for discriminative touch and vibration. Damage impairs these sensations without affecting motor or auditory functions.
9) Which area is involved in proprioception?
a) 3,1,2
b) 4
c) 44,45
d) 41,42
Answer & Explanation: The correct answer is a) 3,1,2. Primary somatosensory cortex interprets proprioceptive input from muscles and joints, enabling body position awareness. Lesions result in impaired joint position sense.
10) Integration of sensory input for spatial orientation occurs in:
a) Areas 5 and 7
b) Areas 3,1,2
c) Areas 4 and 6
d) Areas 41,42
Answer & Explanation: The correct answer is a) Areas 5 and 7. Somatosensory association cortex integrates tactile and proprioceptive information to form spatial awareness, essential for coordinated motor actions and object recognition.
Chapter: Nervous System; Topic: Somatosensory System; Subtopic: Mechanoreceptors
Keyword Definitions:
• Vibration sensation: The perception of oscillatory stimuli applied to the skin, mediated by specialized mechanoreceptors.
• Pacinian corpuscles: Large, encapsulated mechanoreceptors located in deep dermis and subcutaneous tissue, sensitive to high-frequency vibration and pressure.
• Meissner's corpuscles: Superficial dermal mechanoreceptors, detect low-frequency vibration and light touch.
• Merkel's discs: Slowly adapting mechanoreceptors, sensitive to sustained pressure and texture.
• Ruffini endings: Slowly adapting mechanoreceptors detecting skin stretch and joint position.
• Mechanoreceptors: Sensory receptors that respond to mechanical stimuli like pressure, touch, stretch, and vibration.
Lead Question - 2014
Vibrations are felt by ?
a) Meissner's corpuscle
b) Merkel's disc
c) Pacinian corpuscle
d) Ruffini's end organ
Answer & Explanation: The correct answer is c) Pacinian corpuscle. Pacinian corpuscles are large, onion-like encapsulated receptors located in the deep dermis and subcutaneous tissue. They are highly sensitive to high-frequency vibrations (about 250 Hz) and deep pressure. Meissner’s corpuscles detect light touch and low-frequency vibrations, Merkel discs sense pressure and texture, and Ruffini endings respond to skin stretch. Pacinian corpuscles rapidly adapt to stimuli, making them ideal for detecting transient vibrations. Clinically, loss of vibration sense can indicate peripheral neuropathy or dorsal column lesions, affecting proprioception and fine touch perception.
1) Low-frequency vibration is detected by:
a) Pacinian corpuscle
b) Meissner's corpuscle
c) Merkel's disc
d) Ruffini's ending
Answer & Explanation: The correct answer is b) Meissner's corpuscle. Meissner’s corpuscles are superficial dermal receptors that respond to light touch and low-frequency vibrations (30–50 Hz). They allow discrimination of fine textures and small object movements across the skin, important for tactile acuity.
2) Merkel's discs primarily detect:
a) Deep pressure
b) Vibration
c) Sustained pressure and texture
d) Skin stretch
Answer & Explanation: The correct answer is c) Sustained pressure and texture. Merkel’s discs are slowly adapting receptors in the basal epidermis. They provide high-resolution spatial information about objects in contact with the skin and play a key role in tactile discrimination.
3) Ruffini endings sense:
a) High-frequency vibration
b) Skin stretch
c) Light touch
d) Temperature
Answer & Explanation: The correct answer is b) Skin stretch. Ruffini endings, found in dermis and joint capsules, respond to sustained stretch, contributing to the perception of finger position and hand shape. They are slowly adapting mechanoreceptors, unlike Pacinian corpuscles which rapidly adapt to vibration.
4) Which receptor adapts rapidly to stimuli?
a) Merkel's disc
b) Pacinian corpuscle
c) Ruffini ending
d) Free nerve ending
Answer & Explanation: The correct answer is b) Pacinian corpuscle. Pacinian corpuscles respond quickly to changes in stimulus and stop firing if stimulus is constant. Rapid adaptation makes them ideal for detecting vibrations and transient pressure but not sustained pressure.
5) Loss of vibration sense suggests lesion in:
a) Corticospinal tract
b) Dorsal column-medial lemniscus pathway
c) Spinothalamic tract
d) Corticobulbar tract
Answer & Explanation: The correct answer is b) Dorsal column-medial lemniscus pathway. Vibration, fine touch, and proprioception travel via dorsal columns to the brain. Lesions here, due to neuropathy or spinal cord injury, cause contralateral loss of vibration and joint position sense.
6) Pacinian corpuscles are most abundant in:
a) Fingertips
b) Palms
c) Deep dermis of hands and feet
d) Hair follicles
Answer & Explanation: The correct answer is c) Deep dermis of hands and feet. Pacinian corpuscles are concentrated in areas where detection of vibration and pressure changes is critical, allowing precise manipulation of objects and detection of surface textures.
7) Slowly adapting mechanoreceptors include:
a) Pacinian corpuscle
b) Meissner's corpuscle
c) Ruffini endings and Merkel's discs
d) Free nerve endings
Answer & Explanation: The correct answer is c) Ruffini endings and Merkel's discs. These receptors maintain firing during sustained stimuli, enabling detection of skin stretch and pressure. Rapidly adapting receptors like Pacinian corpuscles only respond at onset of stimulus.
8) Which receptor is involved in object manipulation and grip control?
a) Pacinian corpuscle
b) Merkel's disc
c) Meissner's corpuscle
d) Ruffini ending
Answer & Explanation: The correct answer is d) Ruffini ending. Ruffini endings detect skin stretch, providing proprioceptive feedback about finger and hand positions, essential for adjusting grip force during manipulation.
9) High-frequency vibrations are transmitted via:
a) Meissner’s corpuscle
b) Pacinian corpuscle
c) Merkel disc
d) Ruffini ending
Answer & Explanation: The correct answer is b) Pacinian corpuscle. Pacinian corpuscles detect high-frequency vibrations (~250 Hz). Their layered structure filters mechanical changes efficiently, rapidly transducing pressure and vibration signals to sensory neurons.
10) Which receptor is primarily responsible for tactile acuity?
a) Pacinian corpuscle
b) Meissner's corpuscle
c) Ruffini ending
d) Golgi tendon organ
Answer & Explanation: The correct answer is b) Meissner's corpuscle. Meissner corpuscles are densely packed in fingertips and lips, allowing discrimination of fine textures and low-frequency vibration. They support precise tactile perception essential for tasks like reading Braille or handling small objects.
Chapter: Nervous System; Topic: Sensory Systems; Subtopic: Special Senses and Proprioception
Keyword Definitions:
• Sense organ: Specialized structure that detects specific stimuli and transmits sensory information to the central nervous system.
• Efferent supply: Nerve fibers that carry signals away from the CNS to peripheral organs or muscles.
• Golgi tendon organ: Proprioceptive receptor in tendons, senses muscle tension, primarily afferent but some efferent modulation via gamma motor fibers.
• Organ of Corti: Sensory epithelium in cochlea detecting sound; has efferent innervation from olivocochlear bundle.
• Retina: Light-sensitive layer in the eye, primarily afferent via optic nerve.
• Taste bud: Receptor for gustatory stimuli, primarily afferent via cranial nerves VII, IX, X.
Lead Question - 2014
Sense organ which is having efferent supply?
a) Golgi tendon organ
b) Organ of Corti
c) Retina
d) Taste bud
Answer & Explanation: The correct answer is b) Organ of Corti. The Organ of Corti, located in the cochlea of the inner ear, receives efferent fibers from the olivocochlear bundle, which modulate outer hair cell activity to fine-tune cochlear sensitivity and protect from loud sounds. This is unique among sensory organs as most sense organs, like retina and taste buds, receive purely afferent signals. Golgi tendon organs have some efferent gamma modulation, but main efferent supply in sense organs is classically described in the Organ of Corti. Efferent fibers help in auditory gain control and sound discrimination.
1) The efferent fibers to the cochlea originate from:
a) Superior olivary complex
b) Inferior colliculus
c) Cochlear nucleus
d) Lateral geniculate body
Answer & Explanation: Correct answer is a) Superior olivary complex. Efferent fibers of the olivocochlear bundle arise from the superior olivary complex and synapse on outer hair cells, regulating cochlear amplification and protecting against noise-induced damage.
2) Golgi tendon organs detect:
a) Muscle length
b) Muscle tension
c) Joint position
d) Vibration
Answer & Explanation: Correct answer is b) Muscle tension. Golgi tendon organs are proprioceptors embedded in tendons, sensing the force generated by muscle contraction. They prevent excessive tension and potential injury by initiating inhibitory reflexes.
3) Efferent innervation in the Organ of Corti primarily modulates:
a) Inner hair cells
b) Outer hair cells
c) Tectorial membrane
d) Spiral ganglion
Answer & Explanation: Correct answer is b) Outer hair cells. Efferent fibers from the olivocochlear bundle synapse on outer hair cells, controlling their motility. This modulation enhances frequency selectivity and reduces cochlear damage from loud sounds.
4) Retina is supplied by efferent fibers from:
a) Edinger-Westphal nucleus
b) Olivocochlear bundle
c) Facial nerve
d) None
Answer & Explanation: Correct answer is a) Edinger-Westphal nucleus. While retina itself is sensory, parasympathetic efferents from Edinger-Westphal nucleus control pupillary constriction via ciliary ganglion. Direct efferent supply to photoreceptors is absent; main transmission is afferent through optic nerve.
5) Taste buds transmit information via efferent fibers?
a) True
b) False
Answer & Explanation: Correct answer is b) False. Taste buds are purely afferent receptors, sending gustatory information to the brainstem via cranial nerves VII, IX, and X. There is no efferent modulation at the receptor level.
6) Organ of Corti efferent system helps in:
a) Enhancing sound localization
b) Muscle tone regulation
c) Color vision
d) Taste discrimination
Answer & Explanation: Correct answer is a) Enhancing sound localization. The olivocochlear efferent system fine-tunes cochlear output, suppresses background noise, and improves signal-to-noise ratio, aiding precise localization of sound sources.
7) Which of the following has both afferent and efferent innervation?
a) Retina
b) Organ of Corti
c) Taste bud
d) Muscle spindle
Answer & Explanation: Correct answer is b) Organ of Corti. The Organ of Corti uniquely receives afferent signals via spiral ganglion neurons and efferent fibers via the olivocochlear bundle, modulating outer hair cell activity. Other organs like retina and taste buds primarily transmit afferent signals.
8) Lesion of olivocochlear bundle causes:
a) Loss of light touch
b) Increased susceptibility to noise-induced hearing loss
c) Loss of taste
d) Loss of pupillary reflex
Answer & Explanation: Correct answer is b) Increased susceptibility to noise-induced hearing loss. Efferent fibers reduce cochlear amplifier gain and protect outer hair cells. Damage to olivocochlear bundle diminishes this protective mechanism, increasing vulnerability to acoustic trauma.
9) Gamma motor fibers modulate which receptor?
a) Golgi tendon organ
b) Pacinian corpuscle
c) Muscle spindle
d) Organ of Corti
Answer & Explanation: Correct answer is c) Muscle spindle. Gamma motor fibers adjust intrafusal fiber tension, maintaining sensitivity of muscle spindles during muscle contraction, allowing accurate proprioception.
10) Which sense organ has purely afferent function?
a) Organ of Corti
b) Golgi tendon organ
c) Retina
d) Both a and b
Answer & Explanation: Correct answer is c) Retina. The retina converts light into neural signals sent to the brain via optic nerve. Unlike the Organ of Corti, it lacks direct efferent modulation at the receptor level.
Chapter: Nervous System; Topic: Special Senses; Subtopic: Gustation (Taste)
Keyword Definitions:
• Papillae: Small projections on the tongue surface; some contain taste buds. • Fungiform papillae: Mushroom-shaped, mostly at tip and lateral margins of tongue, contain taste buds. • Circumvallate papillae: Large, dome-shaped, located at the posterior tongue in V-shaped row, contain many taste buds. • Foliate papillae: Leaf-shaped, at lateral borders of posterior tongue, contain taste buds. • Filiform papillae: Conical, cover most of tongue surface, primarily tactile, do not contain taste buds.
Lead Question - 2014
False regarding papillae of tongue ?
a) Fungiform papillae at tip
b) Circumvallate papillae at base
c) Foliate papillae at back edge
d) Filiform papillae have taste buds at tip
Answer & Explanation: Correct answer is d) Filiform papillae have taste buds at tip. Filiform papillae are keratinized, conical structures covering the anterior two-thirds of the tongue, specialized for mechanical sensation (touch, texture) rather than gustation. They lack taste buds entirely. Fungiform papillae at tip contain taste buds, circumvallate papillae at base have multiple taste buds in trench, and foliate papillae at lateral posterior edges contain taste buds. Thus, only statement d is false. Understanding papilla distribution is critical for clinical assessment of taste disorders and tongue pathology.
1) Which papillae contain the most taste buds?
a) Fungiform
b) Circumvallate
c) Foliate
d) Filiform
Answer & Explanation: Correct answer is b) Circumvallate. Circumvallate papillae are few but large, located at the posterior tongue, each surrounded by a trench with hundreds of taste buds. They are key for bitter taste detection and are innervated by glossopharyngeal nerve (cranial nerve IX).
2) Taste buds in fungiform papillae are innervated by:
a) Glossopharyngeal nerve
b) Facial nerve
c) Vagus nerve
d) Hypoglossal nerve
Answer & Explanation: Correct answer is b) Facial nerve. Fungiform papillae at anterior tongue tip transmit taste via chorda tympani branch of facial nerve (cranial nerve VII), conveying sweet, salty, and umami sensations.
3) Foliate papillae are most prominent in:
a) Children
b) Adults
c) Elderly
d) Newborns
Answer & Explanation: Correct answer is a) Children. Foliate papillae are leaf-like folds at lateral posterior tongue edges, more prominent in children. They regress with age and contain taste buds mainly sensitive to sour tastes.
4) Filiform papillae function primarily in:
a) Bitter taste
b) Mechanical sensation
c) Sweet taste
d) Saliva secretion
Answer & Explanation: Correct answer is b) Mechanical sensation. Filiform papillae are keratinized, conical, covering most anterior tongue, aiding friction and texture detection. They do not contain taste buds, distinguishing them from gustatory papillae.
5) Circumvallate papillae are innervated by:
a) Facial nerve
b) Glossopharyngeal nerve
c) Vagus nerve
d) Trigeminal nerve
Answer & Explanation: Correct answer is b) Glossopharyngeal nerve. Posterior tongue circumvallate papillae transmit taste via cranial nerve IX, particularly bitter taste, and contain many taste buds arranged in trenches.
6) Which papillae detect sour taste predominantly?
a) Fungiform
b) Foliate
c) Circumvallate
d) Filiform
Answer & Explanation: Correct answer is b) Foliate. Foliate papillae are lateral folds at the posterior tongue with numerous taste buds, particularly sensitive to sour taste. They regress with age, being most functional in children.
7) Tongue papillae without taste buds are:
a) Fungiform
b) Filiform
c) Circumvallate
d) Foliate
Answer & Explanation: Correct answer is b) Filiform. Filiform papillae cover the anterior tongue, specialized for mechanical tasks like texture perception and gripping food. They do not contain taste buds, unlike fungiform, circumvallate, and foliate papillae.
8) Papillae with mushroom-shaped appearance are:
a) Circumvallate
b) Fungiform
c) Foliate
d) Filiform
Answer & Explanation: Correct answer is b) Fungiform. Fungiform papillae are scattered on anterior tongue tip and sides, dome-shaped, contain taste buds, and are innervated by the facial nerve via chorda tympani.
9) Which cranial nerve innervates taste buds in posterior tongue?
a) Facial
b) Glossopharyngeal
c) Vagus
d) Hypoglossal
Answer & Explanation: Correct answer is b) Glossopharyngeal. Cranial nerve IX supplies circumvallate papillae and posterior one-third of tongue, transmitting bitter and other taste sensations to the brain.
10) The majority of tongue surface is covered by:
a) Filiform papillae
b) Fungiform papillae
c) Circumvallate papillae
d) Foliate papillae
Answer & Explanation: Correct answer is a) Filiform papillae. Filiform papillae cover most of anterior tongue, providing mechanical function, friction for food handling, and do not contain taste buds, unlike scattered fungiform papillae.
Chapter: Physiology; Topic: Thermoregulation; Subtopic: Fever Mechanism
Keyword Definitions:
• Fever: Elevation of body temperature due to pyrogenic response to infection or inflammation.
• Prostaglandins (PGs): Lipid mediators derived from arachidonic acid, involved in inflammation, fever, and vascular tone.
• PGE2: Key prostaglandin produced in hypothalamus, mediates fever by elevating set-point.
• PGF2α, PGI2, PGD2: Other prostaglandins with roles in smooth muscle contraction, vasodilation, platelet function, and sleep regulation.
Lead Question - 2014
Fever is produced by ?
a) PGF2α
b) PGE2
c) PGI2
d) PGD2
Answer & Explanation: Correct answer is b) PGE2. Fever occurs when pyrogens (endogenous or exogenous) trigger prostaglandin E2 synthesis in the preoptic area of the anterior hypothalamus. PGE2 elevates the hypothalamic set-point, causing heat-conserving mechanisms like vasoconstriction and shivering, which raise body temperature. Other prostaglandins, such as PGF2α, PGI2, and PGD2, have distinct physiological roles including smooth muscle contraction, vasodilation, platelet inhibition, and sleep regulation, and do not directly mediate fever. Understanding PGE2’s role is crucial for therapeutic interventions with antipyretics like NSAIDs that inhibit cyclooxygenase, thereby reducing PGE2 and fever.
1) Endogenous pyrogens include:
a) IL-1, IL-6, TNF-α
b) PGE2 only
c) Histamine
d) Bradykinin
Answer & Explanation: Correct answer is a) IL-1, IL-6, TNF-α. These cytokines are produced by activated leukocytes in infection or inflammation. They stimulate hypothalamic PGE2 production, raising the temperature set-point and causing fever.
2) NSAIDs reduce fever by inhibiting:
a) Lipoxygenase
b) Cyclooxygenase
c) Phospholipase A2
d) Adenylate cyclase
Answer & Explanation: Correct answer is b) Cyclooxygenase. NSAIDs block COX enzymes, preventing conversion of arachidonic acid to prostaglandins, including PGE2. Reduced PGE2 synthesis lowers hypothalamic set-point, thus decreasing fever.
3) Pyrogen-induced PGE2 acts on which hypothalamic region?
a) Posterior hypothalamus
b) Preoptic anterior hypothalamus
c) Suprachiasmatic nucleus
d) Lateral hypothalamus
Answer & Explanation: Correct answer is b) Preoptic anterior hypothalamus. PGE2 in this region increases the thermoregulatory set-point, leading to heat conservation and generation mechanisms that elevate core body temperature during fever.
4) Fever helps the body by:
a) Reducing metabolic rate
b) Enhancing immune response
c) Causing hypothermia
d) Decreasing leukocyte activity
Answer & Explanation: Correct answer is b) Enhancing immune response. Moderate fever improves leukocyte mobility, enhances phagocytosis, and inhibits growth of certain pathogens, serving as a protective physiological response.
5) Exogenous pyrogens are:
a) Bacterial toxins
b) Cytokines
c) PGE2
d) Histamine
Answer & Explanation: Correct answer is a) Bacterial toxins. Lipopolysaccharide (LPS) and other bacterial products act as exogenous pyrogens, stimulating cytokine release which induces hypothalamic PGE2 synthesis, leading to fever.
6) Which prostaglandin is involved in vasodilation but not fever?
a) PGE2
b) PGI2
c) PGF2α
d) None
Answer & Explanation: Correct answer is b) PGI2. PGI2 (prostacyclin) is mainly produced by endothelial cells, inhibits platelet aggregation, and causes vasodilation. It does not directly mediate hypothalamic set-point elevation or fever.
7) Shivering during fever is triggered by:
a) Decreased set-point
b) Increased hypothalamic set-point
c) Peripheral vasodilation
d) Reduced PGE2
Answer & Explanation: Correct answer is b) Increased hypothalamic set-point. When PGE2 raises the hypothalamic set-point above body temperature, heat-generating mechanisms like shivering and vasoconstriction are activated to reach the new set-point.
8) Antipyretics target fever by:
a) Reducing IL-1 production
b) Inhibiting PGE2 synthesis
c) Stimulating TNF-α
d) Activating PGF2α
Answer & Explanation: Correct answer is b) Inhibiting PGE2 synthesis. Drugs like aspirin and ibuprofen inhibit cyclooxygenase, preventing PGE2 formation, thereby lowering the hypothalamic set-point and alleviating fever.
9) Fever-producing prostaglandin is synthesized from:
a) Cholesterol
b) Arachidonic acid
c) Phosphatidylcholine
d) Linoleic acid
Answer & Explanation: Correct answer is b) Arachidonic acid. Arachidonic acid is released from membrane phospholipids and converted by COX enzymes to PGE2, the key mediator elevating hypothalamic set-point and causing fever.
10) Which prostaglandin is mainly involved in sleep regulation, not fever?
a) PGD2
b) PGE2
c) PGI2
d) PGF2α
Answer & Explanation: Correct answer is a) PGD2. PGD2 is synthesized in the brain, particularly by leptomeninges, promoting sleep and modulating circadian rhythm. Unlike PGE2, it does not induce hypothalamic fever response.