Practical 8

Question 1

What are the components of the deep tendon reflex arc?

Answer 1

• Monosynaptic reflex (possible inhibitory interneuron for antagonists)
• Afferent neuron: Sensory neuron from muscle spindle (DRG)
• Efferent neuron: Alpha motor neuron in ventral horn
• UMNs: Inhibit the relfex

Question 2

What is the role of gamma motor neurons in reflexes?

Answer 2

Adjust spindle sensitivity by maintaining intrafusal fibre tone, especially during muscle contraction.

Question 3

What does a hyperactive vs absent deep tendon reflex indicate?

Answer 3

• Hyperactive: Upper motor neuron lesion
• Absent: Lower motor neuron lesion or peripheral neuropathy

Question 4

What is the Babinski sign and its clinical significance?

Answer 4

• Positive Babinski: Upward toe extension → UMN lesion
• Normal in infants due to unmyelinated corticospinal tract

Question 5

What are the major nuclei of the basal ganglia?

Answer 5

• Striatum: Caudate + Putamen
• Globus pallidus: GPi (output) + GPe
• Subthalamic nucleus
• Substantia nigra: SNc (dopamine) + SNr (output)
• Nucleus accumbens (ventral striatum)

Question 6

What is the function of the direct and indirect pathways?

Answer 6

• Direct (D1): Facilitates movement via disinhibition of thalamus
• Indirect (D2): Inhibits movement via increased thalamic inhibition

Question 7

What is the effect of dopamine on basal ganglia pathways?

Answer 7

• D1 (direct): Dopamine excites → promotes movement
• D2 (indirect): Dopamine inhibits → also promotes movement

Question 8

What motor symptoms are associated with basal ganglia damage?

Answer 8

• Subthalamic nucleus: Hemiballismus (involuntary flinging)
• Striatum: Chorea (involuntary spasms)
• Substantia nigra: Bradykinesia, cogwheel rigidity (Parkinson’s)

Question 9

What are the three functional divisions of the cerebellum and their roles?

Answer 9

• Vestibulocerebellum (flocculonodular): Balance, eye movement
• Spinocerebellum (vermis): Posture, gait, trunk coordination
• Cerebrocerebellum (lateral hemispheres): Planning, skilled movement

Question 10

What types of input does the cerebellum receive?

Answer 10

• Proprioceptive (spinal cord, brainstem)
• Vestibular (balance)
• Cortical (via pontine nuclei)

Question 11

What are common signs of cerebellar lesions?

Answer 11

• Ataxia, intention tremor, dysmetria, dysdiadochokinesia, nystagmus

Question 12

What are the deep cerebellar nuclei and their functional associations?

Answer 12

• Dentate: Cerebrocerebellum
• Interposed (Emboliform + Globose): Spinocerebellum
• Fastigial: Vestibulocerebellum