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Physio: 4# Control of Movements & Posture

Q1. The primary motor cortex is located:

In the postcentral gyrus
In the precentral gyrus anterior to the central sulcus
In the parietal lobe near the sylvian fissure
In the supplementary motor area
Explanation:
The primary motor cortex occupies the first convolution of the frontal lobe, just anterior to the central sulcus.

Q2. More than half of the primary motor cortex is devoted to controlling:

Trunk muscles
Lower limb muscles
Postural muscles
Hand and speech muscles
Explanation:
Disproportionately large cortical representation is devoted to fine motor control of the hands and speech muscles.

Q3. Stimulation of a single neuron in the primary motor cortex typically causes:

A specific movement pattern
Contraction of a single muscle
Bilateral muscle contraction
Inhibition of antagonist muscles only
Explanation:
Motor cortex neurons encode movements, not individual muscles.

Q4. The premotor cortex primarily functions to:

Generate force of muscle contraction
Maintain posture
Develop motor images and movement patterns
Execute reflex movements
Explanation:
The premotor cortex plans complex movement patterns by first creating a motor image.

Q5. Mirror neurons are most important for:

Balance control
Learning motor skills by imitation
Speech production
Postural reflexes
Explanation:
Mirror neurons fire both during execution and observation of movements, enabling imitation learning.

Q6. Contractions elicited from the supplementary motor area are characteristically:

Weak and unilateral
Restricted to distal limbs
Purely reflexive
Bilateral
Explanation:
Supplementary motor area stimulation produces bilateral, body-wide movements.

Q7. Which statement about the cerebellum is TRUE?

It has no direct ability to cause muscle contraction
It initiates voluntary movement
It replaces motor cortex function
It generates reflexes
Explanation:
The cerebellum influences movement indirectly by coordination, timing, and correction.

Q8. The cerebrocerebellum is primarily responsible for:

Equilibrium
Distal limb coordination
Planning sequential voluntary movements
Muscle tone regulation only
Explanation:
The cerebrocerebellum plans voluntary movements in advance and stores procedural memories.

Q9. Which cerebellar division is most involved in coordination of hand and finger movements?

Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum
Flocculonodular lobe
Explanation:
The spinocerebellum coordinates distal limb movements, especially hands and fingers.

Q10. All cerebellar cortical output neurons are:

Excitatory
Cholinergic
Dopaminergic
Inhibitory Purkinje cells
Explanation:
Purkinje cells are inhibitory and provide the sole output from cerebellar cortex.

Q11. The major source of afferent input to the cerebellum is via:

Mossy fibers
Climbing fibers
Purkinje fibers
Parallel fibers
Explanation:
Mossy fibers relay most afferent inputs, including proprioceptive and cortical signals.

Q12. Each Purkinje cell receives powerful excitatory input from:

Multiple mossy fibers
Thousands of parallel fibers only
A single climbing fiber
Deep cerebellar nuclei
Explanation:
Each Purkinje cell receives one climbing fiber, producing a powerful complex spike.

Q13. Deep cerebellar nuclei initially send which signal at the start of movement?

Inhibitory signal to motor cortex
Excitatory signal to enhance movement
No signal
Sensory feedback signal
Explanation:
Movement begins with excitatory output, followed milliseconds later by inhibition to prevent overshoot.

Q14. Intention tremor and dysdiadochokinesia suggest damage to the:

Basal ganglia
Primary motor cortex
Supplementary motor area
Cerebellum
Explanation:
These are classic signs of cerebellar dysfunction.

Q15. The basal ganglia primarily function to:

Select and scale motor programs
Generate reflexes
Maintain muscle tone
Directly contract muscles
Explanation:
Basal ganglia regulate the pattern, intensity, and sequencing of movements.

Q16. The putamen circuit of the basal ganglia is mainly involved in:

Cognitive motor planning
Eye movements
Execution of learned movement patterns
Postural reflexes
Explanation:
The putamen circuit executes learned motor patterns via motor cortical loops.

Q17. Excitation of the direct basal ganglia pathway causes:

Inhibition of the thalamus
Disinhibition of the thalamus
Reduced cortical output
Suppression of movement
Explanation:
The direct pathway reduces GPi inhibition on the thalamus, increasing thalamic output.

Q18. The indirect basal ganglia pathway ultimately results in:

Increased thalamic excitation
Motor facilitation
Disinhibition of motor cortex
Inhibition of thalamic output
Explanation:
The indirect pathway increases inhibition of the thalamus, suppressing competing motor programs.

Q19. Dopamine from substantia nigra increases movement by:

Stimulating D1 and inhibiting D2 pathways
Inhibiting both pathways
Blocking glutamate release
Directly exciting motor neurons
Explanation:
Dopamine excites the direct pathway (D1) and inhibits the indirect pathway (D2), facilitating movement.

Q20. Loss of dopaminergic neurons in substantia nigra is characteristic of:

Huntington disease
Parkinson disease
Amyotrophic lateral sclerosis
Multiple sclerosis
Explanation:
Parkinson’s disease results from degeneration of dopaminergic neurons in the substantia nigra.