ML 5 Vestibular nuclei

Question 1

3 main functions of vestibular nuclei

Answer 1

1. Maintain body balance
2. Vestibulo-ocular reflex
3. Perception of position and motion

Question 2

How does the vestibular nuclei maintain body balance?

Answer 2

• connect with spinal cord and cerebellum
• input: proprioception from muscle spindles (DSCT and VSCT)
• output
  1. vestibulospinal tract - ipsilateral to lateral vestibulospinal tract to antigravity extensors
  2. vestibulocervical reflex - medial vestibular nu. > bilaterally join the descending MLF to cervical spinal cord, control neck muscles

Question 3

How is VOR achieved by the vestibular nucleus?

Answer 3

• directly from vestibular nuclei to CN6 contralaterally and CN3
• input: from inner ear semicircular canal
• output: from superior/ medial vestibular nuclei, to contralateral CN6 nu. and ipsilateral CN3 via MLF (ascending part)

Question 4

How is gain of VOR modulated?

Answer 4

By vestibulocerebellum via visual error signals (retina > ION > climbing fibers)
(HUF)

Question 5

What will happen in tracking eye movement?

Answer 5

VOR will be suppressed via cerebellum connections to vestibular nuclei.

Question 6

Vestibular areas include?

Answer 6

• anterior cingulate gyrus
• inferior parietal lobe
• parietal-temporal-insular region
• near face region of somatosensory area

Question 7

What are the functions of the vestibular areas?

Answer 7

provide a sense of motion, spatial orientation and head position

Question 8

Motor control from the higher centres (HUS 36)

Input and output of the primary motor cortex?

Answer 8

Input: somatosensory cortex (3,1,2), cerebellum (via VL of thalamus, dentate nucleus feedforward), premotor cortex, supplementary motor area.

Output: coritcospinal tract, corticobulbar tract, striatum (basal ganglia), thalamus (indirectly to cerebellum)

Question 9

Premotor area (area 6) (lateral side) 
main function?

Answer 9

• motor programmes (feedforward, executed with minimal attention), motor routines, movements in response to visual and somatosensory cues (*External cues!)

Question 10

Input and outputs of premotor cortex (area 6, lateral)?

Answer 10

Input:
- prefrontal cortex, basal ganglia (via VL thalamus), posterior parietal cortex (area7), contralateral prefrontal cortex

Output:
- primary motor cortex, reticular formation (routine locomotion*), corticospinal tract

Question 11

Main function of the supplementary motor area (area 6, medial)?

Answer 11

Initiate movement (requires planning) - retrieve motor sequences stored in motor memory, internal cues

Question 12

Inputs and outputs of somatosensory area (area 6, medial?)

Answer 12

• inputs: prefrontal cortex: basal ganglia (VL thalamus), contralateral SMA
• outputs: primary motor area, corticospinal tract

Question 13

Frontal eye field functions?

Answer 13

• Voluntary saccadic eye movements towards contralateral visual heme-field. (receive sensory input from prefrontal and posterior parietal cortex)
• Project to superior colliculus (tectum of midbrain) then to PPRF to CN6 and CN3

Question 14

Cerebellum (HUS41)

Name the 3 different parts of cerebellum, the main muscles they innervate and the functions.

Answer 14

1. Vestibulocerebellum (Archi)
   - extensors
   - equilibrium, eye movement
2. Spinocerebellum (Paleo)
   - Medial muscles
   - equilibrium, posture, gait
3. Cerebrocerebellum/ Pontocerebellum (Neo)
   - Distal muscles/ lateral muscles
   - voluntary control of skilled movements (HUF: motor planning and precise timing of movement)