Occulomotor System

Front 1

What are the conjugate vs dysconjugate eye movements?

Back 1

all except vergence are conjugate in which both eyes move together in the same direction

Front 2

What is the pathway for the different eyemovements?

Back 2

1) each eye movement starts out with a different underlying motor nucleus
2) eventually these networks connect with neurons in extraoccular motor nuclei (III, VI, IV)
3) this is the final common pathway to extraoccular muscles

Front 3

What muscles do horizontal eye movements? (2)

Back 3

1)medial rectus
2) lateral rectus

Front 4

Which muscles do upward eye movements? (2)

Back 4

1) superior rectus
2) inferior oblique

Front 5

Which muscles do downward eye movements? (2)

Back 5

1) inferior rectus
2) superior oblique

Front 6

Is the occulomotor nucleus made up of a single motor neuron cell group?

Back 6

no

Front 7

What is in the occulomotor complex? (2)

Back 7

1)occulomotor nucleus (GSE)
2) edinger westphal nucleus (GVE)

Front 8

Where is the trochlear nucleus?

Back 8

caudal midbrain above medial longitudinal fasiculus

Front 9

Where is the abducens nucleus?

Back 9

caudal pons below facial colliculus

Front 10

What are the two populations of neurons in the abducens nucleus?

Back 10

1) lateral rectus motor neurons
2) internuclear neurons that project to the contralateral medial rectus

Front 11

What happen if you lesion the abducens nucleus?

Back 11

you lose ipsilateral lateral rectus and contralateral medial rectus

Front 12

What are saccades?

Back 12

extremely fast rapid eye movements where we can change their direction but not their velocity

Front 13

What are the two types of saccades and where are they originate?

Back 13

voluntary - frontal eye field
involuntary - superior colliculus

Front 14

What is the pathway of the vertical upward?

Back 14

interstitial nucleus of cajal that then go to the occulomotor nuclei for superior rectus and inferior oblique

Front 15

Pathway of vertical downward saccade?

Back 15

rostral interstitial nucleus of medial longitudinal fasiculus

Front 16

What is the pathway of the horizontal saccade? (2)

Back 16

paramedian pontine reticular formation to abducens nucleus and to cervical spine for head and neck movement

Front 17

How does the horizontal gaze pathway work?

Back 17

1) Paramedian pontine reticular formation
2) synapse on abducens nuceleus on same side to innervate lateral rectus
3) cross midline to synapse on occulomotor nucleus
4) send another neuron to the cervical spinal cord
5) synapse on medial rectus muscle from occulomotor nucleus

Front 18

What is gaze?

Back 18

eye movement + neck movement

Front 19

Where does the superior colliculus recieve input from?

Back 19

direct retinal input

Front 20

What is in the superficial layer of the SC?

Back 20

visual map

Front 21

Intermediate layer of SC input, output, function?

Back 21

input: superficial layer, FEF, cerebellum, SN
output: deep layer
function: integration

Front 22

Deep layer of SC input, output, function?

Back 22

input: superficial layer and intermedial layer
output: tectobulbar and tectospinal motor path

Front 23

Where do the tectobulbars go?

Back 23

from deep superior colliculus to occulomotor brainstem centers for reflexive saccadic eyemovements

Front 24

Where do the tectospinals go?

Back 24

from deep superior colliclus to neck muscle motor neurons in cervical spinal cord for reflexive head movements

Front 25

What are the two projections of the FEF to control the SC?

Back 25

direct: FEF projects to SC through corticotectals
indirect: FEF projects to SC through substantia nigra via cotrico-straito-nigral-tectal pathway

Front 26

What is the FEF projections to the posterior parietal cortex

Back 26

FEF has connections with posterior parietal cortex when attention requires voluntary saccade

Front 27

What is the FEF projection indirectly to the SC?

Back 27

1) FEF
2) corticostraites to caudate
3) straitonigrals to SNr
4) Nigrotectals to SC

Front 28

How are the FEF and SC related to the horizontal gaze pathway?

Back 28

1) FEF projects directly to PPRF
OR 1) FEF proejcts to SC which projects to PPRF
2) PPRF projects to ipsilateral abducens and cervical spinal cord

Front 29

What happens if you lesion the FEF or SC alone?

Back 29

transient damage because the other is intact

Front 30

What happens if you lesion both the FEF and SC?

Back 30

permanent damage to ability to make saccade

Front 31

Are smooth eye movements voluntary?

Back 31

no

Front 32

What is the pathway for smooth eye movements?

Back 32

1) see object using visual cortex
2) analyze visual motion using preoccipital area MT and MST
3) corticopontine projections in dorsolateral basilar pontine nuclei
4) calculate appropriate size and velocity of eye movement using occulomotor vermis in cerebellum

Front 33

What is the pathway for the vestibuloocular reflex?

Back 33

1) second order vestibular fibers originate in vestibular complex
2) ascend through medial longitudinal fasiculus
3) synapse on extraocular motor nuclei

Front 34

What is the function of the vestibuloocular reflex?

Back 34

canal specific reflexive compensatory eye movements to maintain fixation during head movement

Front 35

What is an optokinetic movement?

Back 35

oscillating eye movements where there is a slow component to follow the object then a fast component to look at the next object so that you can maintain fixation on an object when the visual scene is moving

Front 36

What is the optokinetic nystagmus?

Back 36

oscillating slow and fast eye movements

Front 37

What is the optokinetic pathway?

Back 37

1) retina and visual cortex
2) pretectal area
3) nucleus reticularis tegmenti pontis (NRTP)
4) flocculonodular cortex of cerebellum

Front 38

What is the pathway for the vergence eye movement?

Back 38

1) visual cortex
2) midbrain vergence center
3) vergence center projects bilaterally to occulomotor nucleus/medial rectus for convergence
3) projects to EW nucleus for accomodation and pupillary constriction

Front 39

Does the vergence pathway involve the MLF?

Back 39

no

Front 40

What happens with a occulomotor nerve lesion?

Back 40

side of lesion has
1)ptosis
2)exotropia
3)myhydriasis
4) ipsilateral loss of vertical eye movements

Front 41

Why do we see the symptoms we see in the occulomotor nerve?

Back 41

side of lesion has
1)ptosis - paralysis of levator palpebrae
2)exotropia - unopposed action of lateral rectus, LR6SO4
3)myhydriasis - disruption of PS fibers to constrictor pupillae
4) loss of vertical eye movements

Front 42

What do you see in sixth nerve palsy?

Back 42

side of lesion will not abduct (esotropia)

Front 43

Why do you see in 6th (abducens nerve) nerve palsy?

Back 43

paralysis of right lateral rectus muscle

Front 44

What do you see in abducens nucleus lesion?

Back 44

ipsilateral paralysis of conjugate horizontal eye movement
1) no ipsilateral abduction
2) no contralateral adduction

Front 45

Why do you see what you see in an abducens nucleus lesion?

Back 45

ipsilateral paralysis of conjugate horizontal eye movement
1) no ipsilateral abduction - because you have ipsilateral lesion of lateral rectus
2) no contralateral adduction because you have lesion of contralateral medial rectus

Front 46

What happens when you have a lesion of the MLF?

Back 46

internuclear opthalomoplegia
1) ipsilateral eye will not adduct in gaze to look at opposite side
2) but medial rectus will contract in convergence
3)nystagmus

Front 47

Why do you see what you see in lesion of MLF?

Back 47

internuclear neurons are disrupted which project to ipsilateral medial rectus but they will contract in convergence since that pathway doesnt go through MLF

Front 48

What do you see in a PPRF lesion?

Back 48

ipsilateral paralysis of conjugate horizontal gaze (eye and head movement)

Front 49

What happens when you have a frontal eye field lesion?

Back 49

contralateral paralysis of conjugate horizontal gaze so eyes are deviated towards side of lesion