CN III, IV, VI Flashcards Preview

Clinical Neuroscience weeks 1-3 > CN III, IV, VI > Flashcards

Flashcards in CN III, IV, VI Deck (42):
1

CN III controls what?

Eye movement--- SR, MR, IR, IO

2

CN IV controls what?

Eye movement--- SO

3

CN VI controls

Eye movement--- LR

4

nucleus of cn 3

midbrain just ventral to superior colliculi

5

nucleus of cn 4

midbrain just ventral to superior colliculi

6

nucleus of cn 6

pons (caudal one half)

7

Describe the multinuclear arrangement of the CNIII

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)

8

What is the facial colliculus

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

9

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

contralateral superior rectus

10

CN IV inervates contralateral or ipsilateral superior oblique?

Contralateral

11

CN III exits where?

midbrain/pons junction

12

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

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

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

ok...so what passes through


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

14

CN III inervates the levator palpebrae superioris which leads to

elevation of upper eyelid

15

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

sympathetic innervation of the tarsal muscle

16

Ciliary muscle produces

change in lens shape, accomodation

17

Medial Rectus moves the eye in what way?

Adduction ( towards nose)

18

Lateral Rectus moves the eye in what direction

Abduction (away from nose)

19

Inferior rectus moves the eye in what direction

down

20

superior rectus

up

21

Superior obliques cause

INTORSION of the eye

22

Inferior obliques cause?

Extorsion of the eye

23

Sympathetic pathway to pupilary dilator muscle. Nucleus lies where

Hypothalamus

24

What is the only cranial nerve that exits the brainstem dorsally

CN IV

25

Which two cranial nerve nuclei controlling eye movement serve contralateral muscles

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

26

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

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.

27

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

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.

28

What is the accomodation reflex

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.

29

What initiates the accomodation reflex

Cortical areas:
- Prefrontal eye fields
- Occipito-parietal eye fields

30

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

yes

31

What is the medial longitudinal fasciculous

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

32

Conjugate lateral eye movement is what?

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

33

Failure of conjugate eye movement =

double vision

34

The regulation of conjugate lateral eye movement is regulated by what

PPRF nucleus

35

Activation of the left PPRF causes what

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

36

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

frontal eye field

37

What are the three cortical centers that control eye movement

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

38

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

corticobulbar

39

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

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

40

So the right frontal eye field activates which PPRF

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.

41

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

POT- parietal occipito temporal area

42

POT directs eye movement contralaterally or ipsilaterally

ipsilaterally.