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.
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: 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 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: 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: 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: 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: 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: 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: 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)