CN III, IV, VI

Question 1

CN III controls what?

Answer 1

Eye movement— SR, MR, IR, IO

Question 2

CN IV controls what?

Answer 2

Eye movement— SO

Question 3

CN VI controls

Answer 3

Eye movement— LR

Question 4

nucleus of cn 3

Answer 4

midbrain just ventral to superior colliculi

Question 5

nucleus of cn 4

Answer 5

midbrain just ventral to superior colliculi

Question 6

nucleus of cn 6

Answer 6

pons (caudal one half)

Question 7

Describe the multinuclear arrangement of the CNIII

Answer 7

five different muscles to control so five separate nuclei

Medial nucleus: Superior Rectus
Dorsal Nucleus: Inferior rectus
Intermediate nucleus: Inferior oblique
Ventral nucles: medial rectus

Edinger Westphal nucleus (parasympathetic to the contractor muscles of the iris)

Question 8

What is the facial colliculus

Answer 8

Where the facial nerve, cranial nerve 7, runs over the top of cranial nerve 6 in the floor of the 4th ventricle

Question 9

All nuclei of the CN III nucleus serve their respective ipsilateral muscles except for the medial nuclei which serves

Answer 9

contralateral superior rectus

Question 10

CN IV inervates contralateral or ipsilateral superior oblique?

Answer 10

Contralateral

Question 11

CN III exits where?

Answer 11

midbrain/pons junction

Question 12

CN III is subject to compression from injury from vascular anomalies called aneurysms why?

Answer 12

Because it is in close juxtaposition to a bunch of intracranial arteries. not going to list them. see notes.

Question 13

Know that CN III, IV, and VI and trigeminal 1 and 2 pass through the cavernous sinus along with the internal carotid artery and sympathetics travelling with the ICA. Any kind of hemorrhage, tumor, infection, aneurysm, and/or inflamatory disease may affect the cavernous sinus and and affect these structures

Answer 13

ok…so what passes through

III, IV, VI, V1 and V2, Internal carotid and sympathetics travelling with ICA

Question 14

CN III inervates the levator palpebrae superioris which leads to

Answer 14

elevation of upper eyelid

Question 15

Autonomic elevation of the eyelid is accomplished through innervation of what by what?

Answer 15

sympathetic innervation of the tarsal muscle

Question 16

Ciliary muscle produces

Answer 16

change in lens shape, accomodation

Question 17

Medial Rectus moves the eye in what way?

Answer 17

Adduction ( towards nose)

Question 18

Lateral Rectus moves the eye in what direction

Answer 18

Abduction (away from nose)

Question 19

Inferior rectus moves the eye in what direction

Answer 19

down

Question 20

superior rectus

Answer 20

up

Question 21

Superior obliques cause

Answer 21

INTORSION of the eye

Question 22

Inferior obliques cause?

Answer 22

Extorsion of the eye

Question 23

Sympathetic pathway to pupilary dilator muscle. Nucleus lies where

Answer 23

Hypothalamus

Question 24

What is the only cranial nerve that exits the brainstem dorsally

Answer 24

CN IV

Question 25

Which two cranial nerve nuclei controlling eye movement serve contralateral muscles

Answer 25

The medial nuclei of CN III (superior rectus) and the trochlear nucleus (superior oblique)

Question 26

The first presenting sign of an aneurysm pressing on the top of CN III will be what?

Answer 26

Unilateral pupilar enlargement due to damage of the parasympathetic constrictor fibers that travel in the upper part of CN III. Unilateral paresis will come on shortly after. This is a neurologic emergency.

Question 27

Paresis of the muscles served by CN III without enlargement of the pupil means?

Answer 27

occlusion of the blood vessels serving the center of CN III as a result of diabetes. The parasympathetic fibers tend to be protected due to their superficial location.

Question 28

What is the accomodation reflex

Answer 28

Involves three things:

1) convergence of the eyes
2) Parasympathetic constriction of the pupil via EW
3) Thickening of the lens due to contraction of the ciliary muscle allowing the suspensory ligaments to relax.

Question 29

What initiates the accomodation reflex

Answer 29

Cortical areas:

• Prefrontal eye fields
• Occipito-parietal eye fields

Question 30

Can accomodation occur in the face of a lesion of MLF >

Answer 30

yes

Question 31

What is the medial longitudinal fasciculous

Answer 31

The connection between cranial nerve 6 (LR) and CN III nuclei that allows for horizontal eye movement

Question 32

Conjugate lateral eye movement is what?

Answer 32

activation of CN VI to cause abduction of the ipsilateral eye will immediately activate the contralateral CNIII nucleus that controls the medial rectus of the oopposite eye

Question 33

Failure of conjugate eye movement =

Answer 33

double vision

Question 34

The regulation of conjugate lateral eye movement is regulated by what

Answer 34

PPRF nucleus

Question 35

Activation of the left PPRF causes what

Answer 35

activation of the left lateral rectus (CNVI) and simultaneous activation of right ventral nucleus to activate CNIII

Question 36

Saccadic eye movement is under the control of which of the cortical centers ?

Answer 36

frontal eye field

Question 37

What are the three cortical centers that control eye movement

Answer 37

1) Visual cortex
2) frontal eye fields
3) parietal-occipito temporal areas

Question 38

The saccadic pathway from the frontal eye field travels with what fibers through the internal capsule

Answer 38

corticobulbar

Question 39

These fibers that travel with the corticobulbar fibers through the internal capsule head where?

Answer 39

to the ipsilateral superior colliculus and then to the contralateral PPRF.

Question 40

So the right frontal eye field activates which PPRF

Answer 40

The left. The left PPRF then activates the left abducens nerve and the right ventral nucleus of CNIII (medial rectus) to make they eys look left.

Question 41

Slow pursuit eye movements are under the control of which of the three cortical centers

Answer 41

POT- parietal occipito temporal area

Question 42

POT directs eye movement contralaterally or ipsilaterally

Answer 42

ipsilaterally.