Final 4 (Eye Movements)

Question 1

Which cranial nerves are involved in the control of the muscles that move the eyes?

Answer 1

3 (III): Oculomotor
4 (IV): Trochlear
6 (VI): Abducens

Question 2

The frontal eye fields and parieto-occipital regions of the brain do not project directly to the eye movement nuclei of cranial nerves 3, 4 and 6 but to other structures that are involved in eye movement control, true or false?

Answer 2

True

Question 3

Brainstem gaze centers are above the level of the ________________, and located where?

Answer 3

Oculomotor nucleus

Brainstem, cerebellum, basal ganglia and the cerebral cortex.

Question 4

What is the function of brainstem gaze centers?

Answer 4

To direct the movements of the eyes, to coordinate and control the response of the eyes to changes in target speed and position, and head position.

Question 5

Brainstem gaze centers are connected to output nuclei (cranial nerves 3, 4, and 6) by…

Answer 5

Inter-nuclear pathways (circuits)

Question 6

Horizontal eye movements are controlled by which muscles?

Answer 6

Lateral rectus and medial rectus

Question 7

The lateral rectus muscle is connected to which cranial nerve nucleus?

Answer 7

Abducens nuclei (cranial nerve 6)

Question 8

The medial rectus muscle is connected to which cranial nerve nucleus?

Answer 8

Oculomotor nuclei (cranial nerve 3)

Question 9

The innervation of the eye movement cranial nerve nuclei depends on…

Answer 9

The direction of the eye movement

Question 10

The paramedian pontine reticular formation (PPRF) is the _________________ gaze center.

Answer 10

horizontal

Question 11

The paramedian pontine reticular formation is the horizontal gaze center, providing input from input from the cortex, the eyes are “told” which way the should move, this is via a tract called…

Answer 11

the medial longitudinal fasciculus

Question 12

Tells the eyes which way they should move via connections with cranial nerves

Answer 12

Medial longitudinal fasciculus

Question 13

The lateral rectus muscle is controlled through connection with which cranial nerve nucleus?

Answer 13

Abducens nuclei (6)

Question 14

The medial rectus muscle is controlled through connection with which cranial nerve nucleus?

Answer 14

Oculomotor (3)

Question 15

Neurons projecting from the abducens nucleus (CN 6) have two pathways (projections), what are they?

Answer 15

1. The lateral rectus
2. Cross and project to the oculomotor nucleus (CN 3) which innervates the medial rectus muscle

Question 16

Neurons in the abducens nucleus cross and project to the oculomotor nucleus via a tract called…

Answer 16

The medial longitudinal fasciculus

Question 17

The rostral interstitial nucleus of the MLF and the interstitial nucleus of Cajal, both in the midbrain are ______________ gaze centers.

Answer 17

vertical

Question 18

The rostral interstitial nucleus of the MLF and the interstitial nucleus of Cajal both project to the ____________ nucleus and the _____________ nucleus thereby controlling the activity of the lower motor neurons that innervate eye muscles involved with vertical movements.

Answer 18

Oculomotor (CN 3)
Trochlear (CN 4)

Question 19

What is the function of saccadic eye movements?

Answer 19

Bring targets of interest into the field of view and refocus the image on the fovea

Question 20

Ballistic conjugate eye movements

Answer 20

Saccades

Question 21

Saccadic eye movements involve direction control, what structure(s) are the horizontal gaze center and the vertical gaze center?

Answer 21

The paramedian pontine reticular formation is the horizontal gaze center.

The rostral interstitial nucleus of the medial longitudinal fasciculus and the interstitial nucleus of Cajal are the vertical gaze centers.

Question 22

For saccadic eye movements both the __________ and __________ communicate with the horizontal and vertical gaze centers, sending motor commands to move eyes in magnitude/direction specified.

Answer 22

Superior colliculus
Frontal eye fields

Question 23

Descending input from the ___________ and the _______________ send motor commands to move eyes in magnitude/direction specified (saccades).

Answer 23

Superior colliculus and frontal eye fields.

Question 24

What type of eye movements require moving stimulus and cannot be carried out voluntarily without a stimulus?

Answer 24

Smooth pursuit eye movements

Question 25

Smooth pursuit eye movements require processing in the _______________ to analyze what an object is, whether is is of interest, direction and speed of movement.

Answer 25

visual cortex

Question 26

Smooth pursuit eye movements can follow a fast moving stimulus, true or false?

Answer 26

False, cannot

Question 27

Smooth pursuit eye movements require a lot of neural processing, true or false?

Answer 27

True

Question 28

Which area of the brain is involved in smooth pursuit eye movements?

Answer 28

Ipsilateral parieto-occipito-temporal cortex (where pathway)

Question 29

What type of eye movement is a slow phase (smooth pursuit) in one direction and fast phase (saccade-like) eye movements in the other?

Answer 29

Optokinetic nystagmus

Question 30

What structure maintains fixation on a target when the head moves, so that the outside world looks stable?

Answer 30

Vestibulo-ocular reflex

Question 31

Horizontal vestibulo-ocular reflex involves which structures?

Answer 31

Vestibular nucleus,
abducens motor nucleus,
medial rectus,
and lateral rectus

Question 32

When the head is turned to the left, explain the mechanism that allows for the gaze to stay on a target?

Answer 32

The vestibulo-ocular reflex:

1. Left semicircular canal activated
2. Left vestibulocochlear CN VIII (8) afferents firing more
3. Recruit right abducens nucleus
   (left abducens nucleus inhibited)
4. Right CN VI (6) and left CN III (3) excited
5. Right lateral rectus and left medial rectus contract
6. Eye movements to the right to oppose head movement