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NS-1 > Control of Eye Movements > Flashcards

Control of Eye Movements Flashcards

1
Q

What parts of the brain achieve control of eye position?

A

medial longitudinal fasciculus

reflexes

cerebral centers

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2
Q

What is saccadic movement?

A

rapid eye movement that brings image of object onto the fovea

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3
Q

What is smooth pursuit?

A

keeps a moving image centered on the fovea

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4
Q

What is vestibular-ocular gaze control?

A

holds image steady on the fovea during head movements

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5
Q

What is vergence?

A

keeps image on fovea when object is moved near

(crossed-eyed)

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6
Q

What is optokinetic gaze control?

A

doing smooth pursuit and moving your head

holds the image steady on the retina during sustained head rotation

visual target is broken whn the target reaches the limit of the visual field –> eyes make a quick move in opposite direction

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7
Q

What are the 5 supranuclear gaze control systems?

A

saccadic

smooth pursuit

vestibular-ocular

vergence

optokinetic

(all are conjugate movements except vergence)

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8
Q

How do you look at a face?

A

tend to focus on eyes, nose, and mouth

saccadic movement jumps around to those areas

your brain doesn’t notice the saccades

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9
Q

If your right frontal eye field sends info to the PPRF, which way are your eyes going to turn?

A

left

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10
Q
A
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11
Q

What is the saccadic horizontal system?

A

frontal eye fields and superior colliculus –> PPRF –> Nucleus 6 –> LR m and Nucleus 3 –> medial rectus m

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12
Q

What is the vertical saccidic system?

A

frontal eye fields and superior colliculus –> rostral interstitial nucleus of the medial long fasciculus (riMLF) –> CN 4 nucleus and CN 3 nucleus

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13
Q

How would a tumor in the pineal gland/ superior midbrain affect vision?

A

selective palsies of vertical gaze = can’t look up

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14
Q

How would tumors of the red nucleus affect vision?

A

have difficulty looking down

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15
Q

What parts of the brain contribute to reflex saccadic eye movements?

A

supplementary and parietal eye fields

soperior colliculus

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16
Q

What are the types of neurons used in saccades?

A
  1. burst of excitatory neurons to move eyes toward target
  2. tonic neuronal firing (tonic neurons) for final locking and fixing of gaze
  3. pause neurons: inhibit burst neurons so no further mvts occur
17
Q

Where are the burst, tonic, and pause cells in the horizontal saccadic system?

A

Burst: PPRF

Tonic: nucleus prepositus hypoglossi (pons)

Pause: omnipause cells of raphe nuclei

18
Q

Where are the burst, tonic, and pause cells in the vertical saccadic system?

A

Burst: rostral interstitial nucleus of MLF (riMLF)

Tonic: interstitial nucleus of cajal (midbrain)

Pause: omnipause cells of Raphe nucleus

19
Q

Where is the PPRF?

A

posterior pons

20
Q

Where are the interstitial cells of cajal and what is there significance?

A

In the midbrain close to red nuclei

hold the tonic cells for the vertical saccadic system

(tumor of red nucleus –> affects ability to look down)

21
Q

How do lesions of the frontal gaze center affect vision?

A

destructive lesion –> eyes deviation toward the side of the lesion (stare at train wreck)

sezure activity (irritative lesion) –> eyes deviate away from the area of irritation (look away from annoying thing)

22
Q

What is the smooth pursuit tract?

A

(R brain signalled –> will look right)

parieto-occipital jxn –> pontine nuclei –> vestublar nuclei and vestibulocerebellum –>

horizontal: CN 6 and 3
vertical: CN 3 and 4

23
Q

What is optokinetic nystagmus?

A

when your eyes are following a target during head motion w/ smooth pursuit

then the target reaches limit of visual field and you can’t see anymore –> eyes make quick move in the opposite direction

24
Q

What parts of the brain are used in the optokinetic reflex?

A

Visual association cortex –> parietooccipital eye field –> nuclei of the accessory optic system and nucleus of the optic tract –> inferior olive, vestibular nuclei, and vestibulocerebellum –> CN nuclei –> muscles

25
Q

How do you test smooth pursuit movements?

A

use optokinetic tape

lesion of parietal lobe –> loss of smooth pursuit movements toward side of lesion = no OKN when tape is moved toward damaged lobe

26
Q

How does turning your head affect the vestibular-ocular system?

A

head is turned right –> activates the right labyrinth –> eyes turn left

27
Q

What is the vestibular-ocular tract?

A

head turns right –> right labyrinth activated –> CN 8 –> vestibular nuclei –> CN VI nucleus –> to lat rectus m and MLF to CN III –> eyes move left slowly

horizontal: CN 6 and 3
vertical: CN 3 and 4

28
Q

How do you test the vestibuloar-ocular reflex?

A

doll’s eye maneuver (on comatose pts): eyes move in opposite direction of head turning

ice water caloric test: COWS; must be conscious to have corrective jerk

29
Q

How will the vestibular-ocular reflex be affected with dysfunction at the level of the brainstem?

A

doll’s eye and ice water calorics will be absent

30
Q

What is the medial longitudinal fasciculus’s significance?

A

connects CN 6 nucleus and CN 3 nucleus

in pons and midbrain

31
Q

What is Internuclear ophthalmoplegia?

A

lesion in medial longitudinal fasciculus (MLF) –> impaired horizontal eye movements

weak adduction of affected eye (ipsi to lesion)

abduction nystagmus of contra eye

convergence is still intact

32
Q

What occurs in left CN 6 nucleus lesion?

A

left eye can’t abduct

right eye can’t adduct (bc of MLF connection)

convergence intact

33
Q

What occurs in left CN VI palsy?

A

left eye can’t abduct

everything else ok

34
Q

What are the 3 parts of the near reflex?

A

convergence

accomodation - lens thickens

pupillary constriction

35
Q

What is the path of the near reflex?

A

optic N –> LGN synapse –> primary visual cortex synapse –> visual association cortex synapse –> CN III nucleus synapse –> to medial rectus m, ciliary m, and pupillary sphincter m

*bypasses MLF entirely

36
Q

What is the Argyll-Roberston pupil?

A

neurosyphilis

absent light reflex, but pupil constricts in near reflex testing

37
Q

What does stimulation of the right PPRF cause?

A

eyes will both move right

(L frontal eye field –> right PPRF –> eyes both look right)

38
Q

What neurotransmitter is responsible for the medial rectus, ciliary, and sphincter m contractions during the near reflex?

A

Ach

39
Q

If someone has normal ice water caloric test, but can’t suppress nystagmus, what part of the brain is damaged?

A

cerebellum

NS-1 (50 decks)

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