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Neuroscience Quiz 3 > 1 Eye Movements > Flashcards

1 Eye Movements Flashcards

1
Q

What are saccades?

A

small jumps in eye movement

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2
Q

What is vergence?

A

the movement of the eye to focus close up or far away

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3
Q

Most movements of the eyes are actually ______ ?

A

reflexes

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4
Q

List the areas of the brain involved in eye movements.

A

retina

vestibular system

cerebral cortex

cerebellum

superior colliculus

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5
Q

What muscles are involved in moving the eye straight up?

A

superior rectus + inferior oblique

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6
Q

What muscles are involved in moving the eye straight down?

A

inferior rectus + superior oblique

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7
Q

What muscles are involved in moving the eye nasally?

A

medial rectus

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8
Q

What muscles are involved in moving the eye temporally?

A

lateral rectus

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9
Q

Sketch the H-test showing what muscles you are testing where.

A
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10
Q

What cranial nerves are involved in eye movement?

A

(SO)4(LR)6-3

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11
Q

Where is the pathway and nuclei of CN III? Where are common aneurysm sites therealong?

A

The GSE nuclei of CN III originate near the midline in the interpeduncular fossa of the midbrain (caudal to the optic chiasm, rostral to the pons) close to the posterior cerebral arteries (common aneurysm site) and the posterior communicating arteries.

  • the Edinger-Westphal nucleus which provides GVE parasympathetic innervation to the lens and pupil is located in the midline in between the two GSE nuclei (their fibers synpase with post-ganglionics in the ciliary ganglion)
  • moves laterally and into the dura
  • courses in the wall of the cavernous sinus
  • innvervates superior rectus, lateral rectus, inferior rectus and levator palpebrae
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12
Q

Pressure on CN III usually first presents as:

A

parasympathetic fibers and is therefore seen as pupillary dilation

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13
Q

.Where is the pathway and nuclei of CN IV?

A
  • trochlear nucleus is in caudal midbrain
  • crosses midline (Only C.N. to do so)
  • exits brainstem at dorsum of the midbrain at caudal midbrain level **only one to exit dorsum of brainstem
  • passes in lat. wall of CAVERNOUS SINUS
  • innervates the contralateral superior oblique muscle

**very thin! (commonly injured in MVAs)

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14
Q

How does CN IV nerve damage manifest itself?

A

eye deviates medially and extorts

pt will have double vision

to correct this, pt wants to intort the contralateral head and does so by tilting the head AWAY FROM the bad eye

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15
Q

Where is the pathway and nuclei of CN VI?

A
  • abducens nuclei at facial colliculus in floor of 4th ventricle in caudal pons
  • exits brainstem at medullary potine jct.
  • courses through center of cavernous sinus
  • innervates ipsilateral lateral rectus
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16
Q

What is the MLF?

A

the medial longitudinal fasciculus (MLF) yokes the two eyes together

Wiki: It connects the cranial nerve nuclei III (Oculomotor nerve), IV (Trochlear nerve) and VI (Abducens nerve) together, and integrates movements directed by the gaze centers (frontal eye field) and information about head movement (from cranial nerve VIII, Vestibulocochlear nerve). It is an integral component of saccadic eye movements as well as vestibulo-ocular and optokinetic reflexes.

It also carries the descending tectospinal tract and medial vestibulospinal tracts into the cervical spinal cord, and innervates some muscles of the neck and upper limbs.

17
Q

What is the PPRF?

A

PPRF = paramedian pontine reticular formation

part of the pontine reticular formation, a brain region without clearly defined borders in the center of the pons; lies next to abducens nucleus

contains neurons that are critical for generating horiz saccades

project to contralateral abducens nucleus

18
Q

What does the superior colliculus do?

A

adjusts the head and eyes towards a stimulus (i.e. its neurons respond to motion)

19
Q

What is the frontal eyefield?

A

lies super above mid sylvian fissure

part of the cortex that among other things controls: premotor cortex patterning of voluntary horizontal gaze

projects to: sup coll and PPRF

20
Q

What directions of eye movements are there (9)?

A
  1. primary gaze
  2. adduction
  3. adbuction (one of each for horiz gaze)
  4. elevation
  5. depression
  6. extorsion (top of eye away from nose)
  7. intorsion (top of eye towards nose)
  8. convergence (bring pupils together)
  9. divergence (bring pupils apart)
21
Q

What is the pathway for vol. horiz. gaze? (e.g. Look ieft)

A

**not how movement is to side contralateral to the side of frontal eye field firing

right frontal eye field –> R sup coll

both to L PPRF

to L CN VI –>L lat rectus

–cxn via MLF to:

R CN III –> R med rectus

22
Q

What is the pathway for vol. vert gaze?

A

.

23
Q

What is the pathway for vestibulo-ocular reflex?

A

.

24
Q

What is the pathway for smooth pursuit?

A

.

25
Q

What is the pathway for vergence?

A

This require the occipital lobes to be intact and the pathway probably involves the superior colliculus. The details of this pathway are less well understood than for some of the other eye movement pathways.

26
Q

What is the pathway for pupillary light reflex?

A
  • light hits retina
  • message travels bilaterally to both pretectal nuclei
  • neuron from both pretectal to respective MLF
  • neuron from each MLF to respective Edinger Westphal nuclei
  • synapse in ciliary ganglion
27
Q

What is the most common complaint related to eye movement?

A

diplopia

28
Q

What types of eye movements are there?

A
  • saccades
    • q3s in humans
    • produced by frontal eye fields (cerebral cortex) or sup. colliculus —>project to paramedian pontine reticular formation (for horiz eye mov’ts) or rostral interstitial nuclei (for vert eye mov’ts)
    • head follows ~20-40msecs afterwards
  • microsaccades
    • prevents image from stay on individual rod/cone too long
      *
29
Q

What disease inhibits saccadic eye mov’t?

A

Parkinson’s dz decreases accuracy of saccades

30
Q

What are the affarents going into the superior colliculus? The efferents leaving it?

A

Affarents

  • retina (light)
  • inferior coll (sound)
  • spinal cord
  • cerebral cortex

Efferents

  • spinal cord (tectospinal tract) and brainstem (tectoreticular) including PPRF and midbrain RF

Neuroscience Quiz 3 (7 decks)

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