CN III, IV, VI Flashcards
what do CN III, IV, VI innervate
somatic motor to extraoccular eye muscles
all extraoccular eye muscles insert where ?
sclera of the eye
what is the function of the superior oblique m. ? inferior oblique m.?
superior oblique - internal rotation
inferior oblique - external rotation
what level of the brainstem would you find the occulomotor nucleus
rostral midbrain
what level of the brainstem would you find the trochlear nucleus
caudal midbrain
what level of the brainstem would you find the abducens nucleus
caudal pons
what is the autonomic preganglionic cell body located beside the occulomotor nucleus , and what muscles does it innervate ?
Edinger-Westphal of PNS
- pupillary sphincter
- ciliary muscle for accomodation
which muscles does CN III have control over, and of those mm. which one is innervated contralaterally
Superior rectus, medial rectus, inferior rectus, inferior oblique
-superior rectus contralaterally the rest are ipsilateral
what would be the autonomic result of an injury to the occulomotor and edingerwestphal nuclei ?
mydriasis - ipsilateral dilated pupil
pupil does not constrict in response to light
can not accomodate for close vision
-happens cuz pupillary constrictor and ciliary mm are dysfunctional
any injury to the occulomotor nucleus would result in ?
ipsilateral damage to extraoccular mm. innervated by CN III
what is a lateral strabismus and what causes it ?
where an eye deviates laterally, caused by lesion to occulomotor nucleus thus making medial rectus dysfunctional
what does CN IV innervate ?
contralateral superior oblique m.
which CN nucleus would course through the red nucleus
occulomotor nucleus cuz its in rostral medulla
what are the results of a lesion in the CN IV nucleus
-much less noticeable than CN III injury (very mild deficit)
-diplopia when reading or going downstairs
-
what is the only CN on the dorsal of the brainstem surface
IV trochlea
what does CN VI innervate
ipsilateral lateral rectus
what is the result of lesion to CN VI
ipsilateral eye damage causing medial strabismus
what is a medail labismus and what causes it
eye is deviated medially b/c of a lesion in the CN VI which innervates lateral rectus
what is the MLF and what does it do
Medial longitudinal fasiculus
-coordinates head and specifically eye nuclei for lateral gazing
internuclear opthalmoplegia is what ?
paralysis of the eye due to damage b/w nuclei
-removes input from occulomotor nucleus
what are the 4 sets of neurons involved in the pupillary light reflex
1 - retinal gangli sends afferent to pretectal nuclei
2 - pretectal nuclei to Edingerwestall nucleus
3- EDW nucleus sends preganglionic PNS fibers to ciliary ganglion
4 - synapse at ciliary ganglion sending postganglionic fibers to contract pupillary sphincter and cilliary m.
accomodation for near vision is controlled by what ?
PNS
what do the short ciliary nerves do ?
postganglionic PNS fibers to tell pupillary sphincter and ciliary mm to contract
in response to accomodation the cisual axis of both eyes tend to converge or diverge ?
converge
what muscles of the eye are activated by the SNS
pupilary dilator, levator palpebrae superioris
what are the 3 conjugate movements of the eye
scanning - 1 target to another in saccades
tracking - smooth pursuit
compensation - gaze held on object during head movement (vestibulocular reflex)
what is a saccade
quick simultaneous movement of eyes
what is responsible for horizontal saccades
paramedian pontine reticular formation (PPRF)
what is responsible for upward saccades
rostral MLF in midbrain
what is responsible for downward saccades
midbrain
what saccade is voluntary
left
