21.10 NS, Control of eye movements

Question 1

Clinical case: boy is tired, his eye (R) turns in. Which muscle is the problem?

Answer 1

Lateral rectus

Question 2

What are saccadic vs. smooth pursuit eye movements?

Answer 2

Saccadic: jerky and rapid

Smooth pursuits: panning

Question 3

What are vestibular ocular and optokinetic

Answer 3

VO: holds image during brief head movements

Optokinetic: eyes flicking when looking at images e.g. through a train

Question 4

What actions do SO and IO have on the eye?

Answer 4

SO (depresses eye)

IO (elevates eye)

Question 5

What are the intraocular muscles innervated by?

Answer 5

SO: IV
LR: VI

Other 4: III

Question 6

Case: MS, double vision when looking to the sides

Answer 6

Inter-nuclear ophthalmic lesion (MLF plaque)

Question 7

What co-coordinates each eye’s movements?

Answer 7

Medial longitudinal fasciculus (white matter tract)

Reticular formation

Question 8

In the brainstem, which parts control horizontal/vertical co-ordination?

Answer 8

Midbrain: vertical gaze (MR/LR)

Pons: horizontal gaze (SO/SR)

Question 9

What are the 2 types of neurons in control of horizontal saccades?

Answer 9

Burst: fire just before movement

Omnipause: Continuous firing (except saccade)

Question 10

What happens if we want to abduct the eyes to the left?

Answer 10

Excitation of burst

Inhibition of burst (inhibit contralateral abducens)

Question 11

What co-ordinates the position of the head and eyes?

Answer 11

Vestibular apparatus

Question 12

What measures the head position and linear acceleration

Answer 12

Head position: semicircular canals

Linear acceleration? Otolith