Neurology (01/30) Cranial Nerves III, IV, and VI

Question 1

separates the motor and sensory pathways in the brainstem

Answer 1

sulcus limitans

Question 2

the difference between the nuclear arrangement of the brainstem and the spinal cord is that the brainstem is ______

Answer 2

discontinuous

Question 3

Cranial nerves III, IV, and VI are all ____ ____ nerves

Answer 3

somatic motor

Question 4

what are the two axon types for CN III?

Answer 4

• somatic motor

- autonomic

Question 5

where is the CNS origin for the somatic motor axon of CN III?

Answer 5

oculomotor nucleus

Question 6

where is the CNS origin for the autonomic axon of CN III

Answer 6

edinger-westphal nucleus

Question 7

what muscles are innervated by the somatic motor axon of CN III

Answer 7

• superior, inferior, medial recti
• inferior oblique
• levator palpebrae superioris

Question 8

what muscles are innervated by the autonomic axon of CN III

Answer 8

• pupillary sphincter
• pupillary ciliary

(after a synapse in the parasympathetic ganglion)

Question 9

both CN IV and VI’s axon types are ____ ____

Answer 9

somatic motor (only! no autonomic)

Question 10

superior oblique is responsible for what type of eye movement from neutral position?

Answer 10

internal rotation (intorsion)

*look down

Question 11

inferior oblique is responsible for what type of eye movement from neutral position?

Answer 11

external rotation (extorsion)

*look up

Question 12

at what level of the midbrain does the oculomotor nerve (III) exit?

Answer 12

upper midbrain

Question 13

at what level of the midbrain does the trochlear nerve (IV) exit?

Answer 13

lower midbrain (crosses ipsilaterally just as it leaves)

Question 14

at what level of the midbrain does the abducens nerve (VI) exit?

Answer 14

lower pons

Question 15

CN III innervates the levator palpebrae superioris muscle ______ (ipsilaterally, bilaterally, contralaterally)?

Answer 15

bilaterally

Question 16

CN III innervates the superior rectus muscle ______ (ipsilaterally, bilaterally, contralaterally)?

Answer 16

contralaterally

Question 17

regarding CN III, the column supplying medial rectus, inferior oblique, inferior rectus are projected to ______ (ipsilaterally, bilaterally, contra laterally) muslces?

Answer 17

ipsilateral

Question 18

regarding CN III, the edinger-westphal nucleus is a preganglionic parasympathetic projection to the _______ ciliary ganglion, and innervates ______ and ______

Answer 18

• ipsilateral
• pupillary sphincter
• pupillary ciliary

Question 19

what are the 7 results of a CN III injury?

Answer 19

• ipsilateral eye to lesion deviates laterally
• cannot move eye medially
• vertical movement is impaired
• diplopia
• ptosis
• mydriasis
• pupil does not constrict or focus for near vision

Question 20

in an injury to CN III, why does the ipsilateral eye deviate laterally?

Answer 20

bc the medial rectus is weak and the lateral rectus is no unopposed so pulls it in that direction (lateral strabismus)

Question 21

in an injury to CN III, why is vertical movement of the eye impaired?

Answer 21

bc there is now a weak superior and inferior recti mm as well as the IPSILATERAL inferior oblique

Question 22

what is diplopia? (happens during injury to CN III)

Answer 22

double vision

Question 23

what is ptosis? (happens during injury to CN III)

Answer 23

droopy eyelid (weak ipsilateral levator palpebrae superioris)

Question 24

what is mydriasis? (happens during injury to CN III)

Answer 24

pupil on affected side is dilated (pupillary dilator m is unopposed as pupillary sphincter and ciliary mm are dysfunctional)

Question 25

where are the cell bodies of CN IV located?

Answer 25

tegmentum

Question 26

CN IV innervates the ______ superior oblique m

Answer 26

contralateral

Question 27

the fibers of CN IV leave the nucleus and turn caudally in paraaqueductal gray, then arch dorsally to decussate and leave the brainstem in _____-_____ junction

Answer 27

midbrain-pons

Question 28

an injury to CN IV is more/less noticeable than an injury to CN III

Answer 28

less

Question 29

an injury to CN IV results in the patient reporting ______ when going downstair or reading

Answer 29

diplopia (double vision)

Question 30

CN that has a long intracranial course that makes is susceptible to increased intracranial pressure (palsy)

Answer 30

CN VI

Question 31

CN VI innervates the _____ lateral rectus m that abducts the eye

Answer 31

ipsilateral

Question 32

where are the cell bodies for CN VI?

Answer 32

in floor of fourth ventricle, caudal pons

Question 33

what two things are medial to the cell bodies of CN VI?

Answer 33

- medial longitudinal fasciculus | - motor fibers of CN VII

Question 34

site where fibers of CN VII wrap around and turn to exit

Answer 34

interanl genu of VII

Question 35

CN VI nucleus and internal genu together are called what?

Answer 35

facial colliculus

Question 36

injury to CN VI NERVE will cause ____ ______ in which the affected eye deviates medially

Answer 36

medial strabismus

Question 37

injury to CN IV NUCLEUS will cause what two things?

Answer 37

- medial strabismus (just like nerve injury) | - lateral gaze paralysis

Question 38

during injury to CN VI, the ______ eye will not abduct past mid position and the _____ eye will not adduct past mid position

Answer 38

- ipsilateral - contralateral *this is due to the fact that the nucleus contains motor neurons and internuclear neurons that ascend the medial longitudinal fasciculus

Question 39

interconects CN's III, IV, and VI nuclei and allows for coordination of head and eye movement. (both eye work together during lateral gaze

Answer 39

medial longitudinal fasciculus

Question 40

injury to the medial longitudinal fasciculus results in what 3 things?

Answer 40

- internuclear ophthalmoplegia (paralysis of the eye due to damage between the nuclei) - removal of excitatory input to ipsilateral III nucleus - ipsilateral eye to lesion fails to move past mid position during horizontal gaze

Question 41

the first neuron in the constriction of pupils in response to light involves an afferent limb that comprised of _____ ____ cells leading to _____ _____

Answer 41

- retinal ganglion | - pretectal nuclei

Question 42

the second neuron in the constriction of pupils in response to light is the pathway that each pretectal nuclei is linked to both _____-______ _____

Answer 42

edinger-westphal nuclei

Question 43

the third neuron in the constriction of pupils in response to light is the preganglionic parasympathetic fibers enter CN ____ and synapse in the _____ _____

Answer 43

- III | - Ciliary ganglion

Question 44

the fourth neuron in the constriction of pupils in response to light is the postganglionic fibers in the short ciliary nerves enter the _____ and ultimately supply the _____ m

Answer 44

- iris | - sphincter

Question 45

at rest, the lens is flattened by tension on its _____ exerted by the _____ _____

Answer 45

- capsule | - suspensetory ligament

Question 46

the lens bulges passively when the ______ m contracts

Answer 46

ciliary

Question 47

to view an object close up: ciliary m ____, which relaxes the lens ______ ligaments

Answer 47

suspensatory

Question 48

during accommodation, both the ______ pupillae m contracts and the ______m contracts

Answer 48

- sphincter | - ciliary

Question 49

when the sphincter pupillae m contracts during accommodation, the decreased light goes through the _____ of the lens (which is thinner)

Answer 49

periphery

Question 50

convergence is when the visual axis of both eyes converge due to increased tone in _____ ____ mm

Answer 50

medial rectus

Question 51

where in the brain do sympathetics to the eye originate from ?

Answer 51

hypothalamus

Question 52

where do preganglionic sympathetics to the eye emerge from the spinal cord?

Answer 52

first thoracic ventral nerve

Question 53

where do the preganglionic sympathies to the eye synapse?

Answer 53

superior cervical ganglion

Question 54

eyes moving as a pair

Answer 54

conjugate movements

Question 55

type of conjugate movement that involves the eyes moving from one visual target to another in high-speed movement known as SACCADES

Answer 55

scanning

Question 56

type of conjugate movement that involves smooth pursuit where the eyes follow an area of interest across a visual field

Answer 56

tracking

Question 57

type of conjugate movement that involves a gaze held on an object of interest during head movement, known as VESTIBULO-OCULAR REFLEX

Answer 57

compensation

Question 58

type of scanning where each pulls eye to its own side

Answer 58

horizontal saccades ***** look at slide 49 to understand this stuff!!!!