Lecture 11: control of eye movements

Question 1

Name the muscles responsible for controlling horizontal eye movements

Answer 1

medial and lateral rectus

Question 2

Name the 3 cranial nerves that control ocular muscles

Answer 2

Oculomotor (3) = medial rectus
Abducens (6) = lateral rectus
Trochlear (4) = superior oblique

Question 3

Describe the different eyemovements

Answer 3

Optokinetic: image moves, head stays still. through motion-sensitive ganglion cells
Saccades: reading words on a page: quick jumps
Nystagmus: combo of optokinetic and saccadic
vestibuloocular: image stays still, head moves

Question 4

Explain the circuitry of saccadic movements

Answer 4

PPRF (paramedian pontine reticular formation) usually inhibits omnipause neurons. during saccade, no inhibition, therefore inhibitory and excitatory burst neurons can fire, this goes to abducens and causes eyes to move in tandem

Question 5

Explain circuitry of vestibuloocular reflex

Answer 5

vestibular apparatus senses head movement (ex. head moves left, sensed by left vestibular apparatus hair cells. right vestibular nuclei are inhibited). leads to inhibition of abducens on left side, activation of abducens on the right side. this causes ipsilateral activation of lateral rectus, contralateral activation of medial rectus through the oculomotor nerve. therefore the eyes turn to the right.