Motor Control Systems — MCQs
Loss of striatal fibres in caudate nucleus is associated with?
A child presented with weakness of limbs, cannot sit properly and swaying both sides while walking. The lesion is in
A 10-year-old boy cuts his finger with a pocketknife and immediately applies pressure to the damaged area with his other hand to partially alleviate the pain. Inhibition of pain signals by tactile stimulation of the skin is mediated by which type of afferent neurons from mechanoreceptors?
Which part of the brain is involved in regulating balance and coordination?
Intention tremor, drunken gait and scanning speech together point towards involvement of
Cerebellar damage causes all of the following except?
Which tract is responsible for the loss of proprioception and fine touch?
Lesion of globus pallidus causes
Spinal pathway mainly regulating fine motor activity?
Characterized by chronic, multiple tics, what is the condition?
Motor Control Systems Indian Medical PG Practice Questions and MCQs
Question 1: Loss of striatal fibres in caudate nucleus is associated with?
- A. Hemiballismus
- B. Huntington's disease (Correct Answer)
- C. Charcot-Marie-Tooth disease
- D. Parkinson's disease
Explanation: ***Huntington's disease*** - This neurodegenerative disorder is pathologically characterized by **atrophy of the striatum**, particularly the **caudate nucleus** [1]. - The loss of striatal neurons, especially medium spiny neurons, leads to the characteristic **chorea** and cognitive decline [1]. *Hemiballismus* - Characterized by **unilateral, violent, flinging movements** of the limbs. - It is typically caused by a lesion in the **subthalamic nucleus**, not the caudate nucleus. *Charcot-Marie-Tooth disease* - A group of inherited disorders that affect the **peripheral nerves**, leading to muscle weakness and sensory loss. - This condition does not involve the degeneration of the striatal fibers in the caudate nucleus. *Parkinson's disease* - Primarily caused by the degeneration of **dopaminergic neurons** in the **substantia nigra pars compacta**. - While it affects the basal ganglia circuitry, its primary pathology is not the loss of striatal fibers in the caudate nucleus but rather a **dopamine deficiency**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1299-1300.
Question 2: A child presented with weakness of limbs, cannot sit properly and swaying both sides while walking. The lesion is in
- A. Neocerebellum
- B. Cerebellopontine area
- C. Cerebellar vermis (Correct Answer)
- D. Cerebellar hemisphere
Explanation: ***Cerebellar vermis*** - Lesions in the **cerebellar vermis** typically cause **truncal ataxia**, leading to difficulty sitting upright and a wide-based gait with swaying [1]. - The vermis is responsible for coordinating **proximal and trunk movements**, which are essential for maintaining balance and posture. *Neocerebellum* - The neocerebellum (lateral hemispheres) is primarily involved in **fine motor coordination** and planning of voluntary movements [1]. - Lesions here typically result in **appendicular ataxia**, affecting movements of the limbs (e.g., dysmetria, dysdiadochokinesia), rather than truncal instability [1]. *Cerebellopontine area* - The cerebellopontine angle (CPA) is a region at the base of the brain where the cerebellum, pons, and medulla meet. - Lesions in this area often present with **cranial nerve palsies** (especially CNs VII and VIII), along with ataxia, but not specifically isolated truncal ataxia. *Cerebellar hemisphere* - Similar to the neocerebellum, the cerebellar hemispheres are primarily involved in **coordinating limb movements**. - Lesions here would typically cause **ipsilateral appendicular ataxia**, affecting the limbs on the same side as the lesion, rather than severe truncal instability [1].
Question 3: A 10-year-old boy cuts his finger with a pocketknife and immediately applies pressure to the damaged area with his other hand to partially alleviate the pain. Inhibition of pain signals by tactile stimulation of the skin is mediated by which type of afferent neurons from mechanoreceptors?
- A. Aδ
- B. Type C
- C. Aβ (Correct Answer)
- D. Aα
Explanation: ***Aβ*** - **Aβ (A-beta) fibers** are large, myelinated afferent neurons that transmit discriminative touch and proprioception. - According to the **gate control theory of pain**, activation of these Aβ fibers by tactile stimulation can inhibit the transmission of pain signals (carried by Aδ and C fibers) in the spinal cord, explaining why rubbing an injured area can reduce pain. *Aδ* - **Aδ (A-delta) fibers** are thinly myelinated afferent neurons that transmit sharp, localized, and fast pain, as well as cold and touch. - While they are involved in pain transmission, they do not primarily mediate the inhibition of pain signals through tactile stimulation, but rather the initial painful sensation. *Type C* - **Type C fibers** are unmyelinated afferent neurons that transmit slow, dull, aching, and burning pain, as well as warmth and some touch. - These fibers are primarily responsible for the prolonged, chronic pain sensation and are inhibited by Aβ fiber activity, not the mediators of the pain inhibition themselves. *Aα* - **Aα (A-alpha) fibers** are the largest and fastest myelinated afferent neurons, primarily responsible for proprioception from muscle spindles (sensory information about muscle length and stretch), and motor innervation to extrafusal muscle fibers. - They are not directly involved in the tactile inhibition of pain signals.
Question 4: Which part of the brain is involved in regulating balance and coordination?
- A. Cerebellum (Correct Answer)
- B. Thalamus
- C. Medulla
- D. Cerebrum
Explanation: ***Cerebellum*** - The **cerebellum** plays a crucial role in coordinating voluntary movements, maintaining balance, and regulating muscle tone [1]. - It receives sensory input from the spinal cord and other parts of the brain and integrates this information to control fine motor skills and posture [1]. *Thalamus* - The **thalamus** primarily acts as a relay station for sensory information, sending it to the cerebral cortex for processing [2]. - It does not directly control balance or coordination, though it processes sensory data critical for these functions [2]. *Medulla* - The **medulla oblongata** primarily controls vital autonomic functions like breathing, heart rate, and blood pressure. - While it helps maintain posture, its primary role is not in the fine-tuning of balance and coordination. *Cerebrum* - The **cerebrum** is responsible for higher-level functions such as thought, voluntary movement, language, and perception. - While it initiates voluntary movements, the **cerebellum** is responsible for refining and coordinating these movements for balance and precision [1].
Question 5: Intention tremor, drunken gait and scanning speech together point towards involvement of
- A. Medulla
- B. Midbrain
- C. Cerebellum (Correct Answer)
- D. Cerebral cortex
Explanation: ***Cerebellum*** - **Intention tremor**, **drunken gait (ataxia)**, and **scanning speech (dysarthria)** are classic signs of **cerebellar dysfunction** [1]. The cerebellum is crucial for coordinating voluntary movements, balance, and motor learning [2]. - Damage to the cerebellum impairs the brain's ability to smoothly execute movements and maintain posture, leading to these characteristic symptoms [2]. *Medulla* - The medulla oblongata primarily controls vital autonomic functions such as **breathing**, **heart rate**, and **blood pressure**. - While damage to the medulla can cause neurological deficits, it typically presents with problems in these vital functions, cranial nerve palsies, or specific sensory/motor deficits, not the classic triad of cerebellar signs. *Midbrain* - The midbrain plays a role in **motor control**, **eye movements**, and processing **auditory and visual information**. - Lesions in the midbrain commonly result in symptoms like oculomotor deficits, pupillary abnormalities, and specific motor pathways involvement (e.g., Parkinsonian symptoms if substantia nigra is affected), rather than the cerebellar signs mentioned. *Cerebral cortex* - The cerebral cortex is responsible for higher cognitive functions, voluntary movement initiation, sensory perception, and language. - Damage to the cerebral cortex typically leads to symptoms such as **hemiparesis**, **aphasia**, **sensory loss**, or **cognitive deficits**, which are distinct from the signs of cerebellar involvement.
Question 6: Cerebellar damage causes all of the following except?
- A. Ataxia
- B. Past-pointing
- C. Dysmetria
- D. Hypertonia (Correct Answer)
Explanation: ***Hypertonia*** - Cerebellar lesions typically lead to **hypotonia**, a decrease in muscle tone, rather than hypertonia [1]. - Hypertonia, or increased muscle tone, is more commonly associated with lesions of the **upper motor neurons** or **basal ganglia** [2]. *Dysmetria* - **Dysmetria** is a common sign of cerebellar damage, characterized by an inability to accurately control the **range, direction, and force** of muscle movements [1]. - This leads to overshooting or undershooting a target during voluntary movements. *Ataxia* - **Ataxia**, particularly truncal or appendicular ataxia, is a cardinal symptom of cerebellar dysfunction [3]. - It refers to a lack of **voluntary coordination** of muscle movements, leading to an unsteady gait and impaired balance [3]. *Past-pointing* - **Past-pointing** is a form of dysmetria where a patient consistently points or reaches **beyond their target** [1]. - It is a specific sign that indicates a deficit in the cerebellum's ability to modulate and refine motor commands.
Question 7: Which tract is responsible for the loss of proprioception and fine touch?
- A. Anterior spinothalamic tract
- B. Lateral spinothalamic tract
- C. Dorsal column (Correct Answer)
- D. Corticospinal tract
Explanation: ***Dorsal column*** - The **dorsal column-medial lemniscus pathway** is responsible for transmitting **fine touch**, **vibration**, and **proprioception** from the body to the cerebral cortex. - Damage to this tract (e.g., in **tabes dorsalis** or **vitamin B12 deficiency**) leads to a loss of these sensations. *Anterior spinothalamic tract* - This tract primarily conveys crude touch and pressure sensations. - While it carries tactile information, it does not transmit the fine discriminative touch or proprioception associated with the dorsal columns. *Lateral spinothalamic tract* - This pathway is responsible for transmitting **pain** and **temperature** sensations. - It does not play a role in proprioception or fine touch. *Corticospinal tract* - The **corticospinal tract** is a **motor pathway** responsible for voluntary movement. - It has no role in transmitting sensory information such as proprioception or fine touch.
Question 8: Lesion of globus pallidus causes
- A. Chorea
- B. Athetosis (Correct Answer)
- C. Hemibalismus
- D. Dystonia
Explanation: ***Athetosis*** - **Athetosis** is the **classic movement disorder** associated with lesions of the **globus pallidus**, often occurring with **putamen** involvement. - It is characterized by **slow, writhing, involuntary movements**, particularly affecting the **distal extremities** (hands and feet). - Commonly seen in **kernicterus** (bilirubin-induced damage to basal ganglia), **cerebral palsy**, and **status marmoratus** of the basal ganglia. - When combined with chorea, it forms **choreoathetosis**. *Chorea* - **Chorea** is predominantly associated with dysfunction of the **caudate nucleus** and **putamen**, as seen in **Huntington's disease**. - It involves brief, irregular, unpredictable, **involuntary movements** that flow from one body part to another. *Hemibalismus* - **Hemibalismus** is most commonly caused by a lesion in the **subthalamic nucleus** (nucleus of Luys), often due to a **lacunar stroke**. - It involves large-amplitude, **involuntary flinging movements** of the limbs on **one side of the body**. *Dystonia* - **Dystonia** involves sustained or repetitive muscle contractions leading to twisting movements or abnormal fixed postures. - It results from dysfunction of **multiple basal ganglia structures** including the globus pallidus internal segment, putamen, and thalamus, but is **not the classic presentation** of isolated globus pallidus lesions.
Question 9: Spinal pathway mainly regulating fine motor activity?
- A. Lateral corticospinal tract (Correct Answer)
- B. Vestibulospinal tract
- C. Anterior corticospinal tract
- D. Reticulospinal tract
Explanation: ***Lateral corticospinal tract*** - This pathway contains **85-90% of corticospinal fibers** that cross at the medullary pyramids and descend in the **lateral funiculus** of the spinal cord - It is the **primary pathway for fine, precise, voluntary movements** of **distal extremities**, particularly the hands, fingers, feet, and toes - Enables intricate skilled movements like writing, buttoning, and fine manipulation due to direct monosynaptic connections to motor neurons - Damage results in loss of fine motor control and skilled movements *Anterior corticospinal tract* - Contains only **10-15% of corticospinal fibers** that descend uncrossed in the anterior spinal cord - Controls **bilateral movements of axial and proximal muscles** (neck, trunk, shoulders) - Not specialized for fine motor control of distal limbs *Vestibulospinal tract* - Regulates **posture and balance** by modulating extensor muscle tone - Coordinates head position and maintains upright posture - Does not control fine voluntary movements *Reticulospinal tract* - Modulates **muscle tone, posture, and locomotion** - Provides general motor control and autonomic regulation - Not specialized for precise, intricate fine motor movements
Question 10: Characterized by chronic, multiple tics, what is the condition?
- A. Parkinson's disease
- B. Wilson's disease
- C. Shy-Drager syndrome
- D. Tourette's syndrome (Correct Answer)
Explanation: ***Tourette's syndrome*** - This syndrome is defined by **multiple motor tics** and at least one **vocal tic** that persist for more than one year. - Tics in Tourette's syndrome are typically **sudden**, rapid, recurrent, nonrhythmic **movements** or vocalizations. *Parkinson's disease* - Characterized by **tremor at rest**, **bradykinesia**, **rigidity**, and postural instability. - While it involves movement disorders, it does not typically present with the characteristic tics seen in Tourette's. *Wilson's disease* - An **autosomal recessive disorder** causing excessive copper accumulation in the liver, brain, and other organs. - Manifestations include **hepatic dysfunction**, neurologic symptoms like **tremor** and **dystonia**, and **Kayser-Fleischer rings**, not tics. *Shy-Drager syndrome* - This is an older term for **multiple system atrophy (MSA)**, a progressive neurodegenerative disorder. - It primarily affects the **autonomic nervous system**, leading to **orthostatic hypotension**, cerebellar ataxia, and parkinsonism, but not tics.
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