Eye Movement

Question 1

What eye muscles does CN III supply

Answer 1

IO, SR, MR, IF

Question 2

What eye muscles does CN IV supply

Answer 2

SO

Question 3

What eye muscles does CN VI supply

Answer 3

LR

Question 4

What test can be done to test the eye movements

Answer 4

H test

Question 5

Pathway to move eye right,

Answer 5

From the left frontal eye field, the medial long fasicularis will project to the reticular formation. The reticular formation will then signal to the abducens on the ipsilaateral side. The abduucens will then directly project to the LR on the ipsilateral side. It will also project to the CNIII nucleus, which will project to MR. Now the eye will move right. This passes the basal ganglia and the superior colliculi.

Question 6

Describe the inhibition pathway

Answer 6

Abducens will also project to controlateral abducens to inhibit it. Now LR on the ipsilateral side will be inhibited and the CNIII nuclei on the contralateral side will be inhibited.

Question 7

Describe the different regions of the RF regarding site

Answer 7

The pontine paramedian RF controls horozontal movement (CNVI and CNIII) while the msencephalic paramedian RF controls vertical movement (CNIV and CNIII)

Question 8

Describe the different neurons in the RF

Answer 8

Burst neurons which fire just before movement and will synapse with the LMN of the cranial nerves. Inhibitory burst neurons to inhibit the antagonistic muscles. Omnipause neurons which continually fire AP except during saccade movement

Question 9

What is the purpose of the vestibulo-ocular refelx

Answer 9

To keep eyes still and focused during rocky and random movements

Question 10

Describe the regions of the vestibular system responsible for this reflex

Answer 10

The Semicircular canals: head position

Otolith: linear acceleration

Question 11

Describe the pathway of the vestibulo-ocular refelx

Answer 11

Changes in head movement will influence the movement of the endolymph in the ampulla in the semicircular canals. This will promote the movement of the capula and increrased firing of CNVIII. This will project directly to CN III on the ipsilateral side and CNVI on the lateral side. Now the regular pathway ensures to ensure agonistic and antagonistic stimulation. However the CN VIII nuclei will also inhibit the ipsilateral Abducen nuclei.