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Central Nervous System

3 out of 5

True about cerebellum

A Cerebral cortex have mostly inhibitory effects

B Co-ordination

C Planning of motor movements

D Decreased tone

E Excitatory effect from deep nuclei

Ans. B Co-ordination

a. Deep cerebellar nuclei are inhibited by the signals arising from purkinje cells while direct stimulation of the deep nuclear cells by both climbing and the mossy fibers excites them. Normally, the balance between the two effects is slightly in favors of excitation.

b. The input signal from motor cortex or brainstems at first greatly increases deep nuclear cell excitation. Then, a few milliseconds later, feedback inhibitory signals from purkinje cells circuit occur.

  1. The afferent inputs to the cerebellum Q

a. Climbing fibers: from inferior olives of medulla Q

b. Mossy fibers: from higher brain, brainstem and spinal cord. Q

  1. Therefore, cerebral cortex has excitatory effect Q.

a. Output of cerebellum:

i. purkinje cells ii. deep cerebellar nuclei

b. Lesions of cerebellum causes:

i. In coordination ii. Intention tremor

iii. Disorder of equilibrium and gait iv. Diminished muscle tone

Functions of cerebellum

  1. Vestibulo cerebellum - equilibrium, gaze Q
  2. Spino cerebellum – coordination, Posture Q
  3. Arcaheo cerebellum - planning and programming of skilled movements. Q