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Neuro Part 2 > Week 5.3 > Flashcards

Week 5.3 Flashcards

1
Q

What are the three major types of eye movements?

A
  • saccades
  • smooth pursuit
  • vestibulo-ocular
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2
Q

What are saccades?

A

quick step changes in eye position as the visual field is scanned

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3
Q

What is the neural pathway for voluntary saccades?

A
  • frontal eye fields
  • superior colliculus
  • reticular formation
  • oculomotor nucleus
  • eye muscles
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4
Q

What are reflex saccades?

A

saccades in response to novel stimuli appearing in the visual field

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5
Q

What is the neural pathway for reflexive saccades?

A
  • retinal ganglion cells
  • superior colliculus
  • reticular formation
  • oculomotor nucleus
  • eye muscles
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6
Q

Voluntary saccades are mediated by the ___ while reflexive saccades are mediated by the ___.

A
  • frontal eye fields

- superior colliculus

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7
Q

What are smooth pursuit eye movements?

A

those used to track an object through the visual field with the head stationary

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8
Q

Smooth pursuit eye movements are limited in what way?

A

they are limited to 30 degrees per second

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9
Q

Smooth pursuit eye movements are triggered by what?

A

slip of the image on the retina

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10
Q

What is the neural pathway for smooth pursuit eye movements?

A
  • retinal ganglion cells
  • LGN
  • visual cortex
  • reticular formation
  • oculomotor nucleus
  • eye muscles
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11
Q

What is the vestibulo-ocular reflex?

A

the compensatory adjustment of gaze when the head moves

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12
Q

What is the maximum velocity of saccades, smooth pursuit movements, and the vestibulo-ocular reflex?

A
  • saccades: 400-700 degrees/second
  • smooth: 30 degrees/second
  • VOR: 300 degrees/second
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13
Q

What is the neural pathway for the vestibulo-ocular reflex?

A
  • vestibular hair cell
  • vestibular nerve
  • vestibular nucleus
  • oculomotor nucleus
  • eye muscle
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14
Q

What brain structure primarily mediates voluntary saccades, reflexive saccades, smooth pursuit, and the vestibulo-ocular reflex?

A
  • voluntary saccades: frontal eye fields
  • reflexive saccades: superior colliculus
  • smooth pursuit: visual cortex
  • VOR: vestibular nucleus
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15
Q

Describe the layers of the vestibular apparatus.

A

temporal bone surrounding perilymph surrounding membranous labyrinth surrounding endolymph

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16
Q

Name the two vestibular organs.

A
  • semicircular canals

- otolith organs

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17
Q

What are the otolith organs?

A

utricle and saccule

18
Q

What are the adequate stimuli for the kinetic labyrinth?

A
  • rotational forces

- head acceleration and deceleration

19
Q

What are the adequate stimuli for the static labyrinth?

A
  • maintained head tilt

- translational forces, horizontal displacement

20
Q

The semicircular canals send impulses along the ____ division of the ___ nerve to the ____.

A
  • superior division
  • vestibular nerve
  • central vestibular pathways
21
Q

What is a functional pair within the semicircular canals?

A

two canals within the same plane but in different sides of the head

22
Q

The horizontal semicircular canals are actually in what plane?

A

one thirty degrees below horizontal

23
Q

The semicircular canals are attached to what structure?

A

the utricles

24
Q

Where in the semicircular canals are the vestibular hair cell receptors?

A

the ampulla

25
Q

What is the cupulla?

A

a gelatinous mass into which the cilia of vestibular hair cells are inserted

26
Q

What is scarpa’s ganglion?

A

the cell bodies of the 8th nerve vestibular afferents

27
Q

What is a kinocilium?

A

the single long cilium of a vestibular hair cell

28
Q

Describe the orientation of kinocilium.

A
  • near the utricle in the horizontal canals

- away from the utricle in the anterior and posterior canals

29
Q

Vestibular hair cells use what NT to affect the 8th nerve afferents?

A

glutamate

30
Q

What causes depolarization of vestibular hair cells?

A

bending of the stereocilia toward the kinocilium

31
Q

Describe the flow of endolymph through the horizontal canals as you move your head from side to side.

A
  • initially, endolymph moves relatively slower than hair cells and thus “opposite” head movement
  • later, inertia causes endolymph to continue moving relative to hair cells and therefore in the direction of herd movement
32
Q

Describe 8th nerve activity in response to the three phases of rotation to the right.

A
  • acceleration to the right: increased right nerve activity, decreased left nerve activity
  • constant velocity: tonic activity (endolymph is equilibrated)
  • deceleration: decreased right nerve activity, increased left nerve activity
33
Q

In the post-rotational phase of the Barany chair test, you expect a person to fall in which direction?

A

fall in the direction of rotation

34
Q

Describe the neural pathway that causes one to fall in the direction of rotation during the post-rotational phase of the Barany chair test.

A
  • decreased 8th nerve firing on rotational side
  • decreased firing rate of vestibulospinal neurons
  • inhibition of extensors on the right
  • flexion to the right (aka fall/tilt)
35
Q

What eye movements are expected in the post-rotational phase of movement?

A

slow movement in the direction of rotation followed by a fast rest in the opposite direction

36
Q

Falling and the typical eye movements in the post-rotational phase of movement are mediated by output from the vestibular nucleus to where?

A

the vestibulospinal tract and oculomotor nuclei, respectively

37
Q

What are the features of internuclear ophthalmoplegia?

A
  • inability to adduct affected eye

- nystagmus in the unaffected eye

38
Q

Internuclear ophthalmoplegia is the result of a lesion to what?

A

the medial longitude fasciculus, which contains the abducens interneurons that transmit signals to the 3rd nerve nucleus for contraction of the medial rectus

39
Q

What are the expected effects of a cold and hot caloric test?

A
  • cold: nystagmus toward the contralateral side
  • warm: nystagmus toward the ipsilateral side
  • COWS (cool opposite, warm, same)
40
Q

In someone with a unilateral lesion of the vestibular nerve, what symptoms can be expected?

A
  • fall toward the ipsilateral side

- nystagmus to the contralateral side

Neuro Part 2 (18 decks)

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