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Block 5; Week 2 > Vestibular-Sievert > Flashcards

Vestibular-Sievert Flashcards

1
Q

What makes up the vestibular apparatus?

A

3 semicircular canals

2 otolith organs–utricle & saccule

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2
Q

Which parts of the vestibular apparatus detect rotational movements?

A

the 3 semicircular canals

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3
Q

Which parts of the vestibular apparatus detect linear acceleration & head tilts?

A

utricle & saccule

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4
Q

What causes tinnitus & vertigo?

A

overproduction of endolymph

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5
Q

T/f The cochlea is a part of the vestibular apparatus that does NOT have channels for endolymph & paralymph.

A

False.

the cochlea & the semicircular canal, otolith portions of the vestibular apparatus have channels for this.

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6
Q

T/F The 3 semicircular canals are set up in 2 planes. 2 of them are parallel.

A

False. They are set up in 3 planes. At 90 degrees to one another.

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7
Q

What is found in the utricle & saccule?

A

big open spaces, air cells.

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8
Q

Are the hair cells found in the vestibular system similar to those found in the auditory system?

A 
Yes.
one kinocilium
stereocilia to one side of the kinocilium.
have ion channels
bathed in a gelatinous fluid
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9
Q

Which parts of the vestibular system have hair cells?

A

the semicircular canals & the utricle & saccule

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10
Q

Where are the hair cells found in the semicircular canals?

A

in the ampulla

embedded in the cupula (a gelatinous mass)

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11
Q

The kinocilium is activated when the stereocilia bend towards/away it.

A

Towards it. Inhibited when they bend away from them.

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12
Q

What are the hair cells found in, in the utricle & saccule?

A 
found in a gelatinous mass
have otoconia (little stones) on top. (these can excite or inhibit the kinocilium)
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13
Q

What is one treatment for positional vertigo?

A

you can sometimes go to the physical therapist & move your head into certain positions & reestablish where the otoconia are.

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14
Q

What ultimately causes the hair cells in the cupula of the semicircular canals to be excited or inhibited?

A

Ultimately, this is caused by the movement of the fluid thru the canal.

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15
Q

T/F Fluid can only move half way through the semicircular canal of the vestibular apparatus.

A

FALSE. It can move all the way around.

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16
Q

What happens to the fluid in the canal when you first start rotation v. when you have been in rotation for a while?

A

First start rotation: fluid lags & relatively moves in the opposite direction of the rotatory movement
After a while: fluid keeps rotating in direction of rotation even after the movement stops.

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17
Q

So…say we are focused on your left ear. You move your head (& therefore your semicircular canal) to the LEFT. Which direction does the fluid go? What does this mean for stimulation of hair cells?

A

The fluid will go to the right at first. This pushes the stereo cilia against the kinocilium. This activates the hair cells.

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18
Q

So…say we are focused on your left ear. You move your head (& therefore your semicircular canal) to the RIGHT. Which direction does the fluid go? What does this mean for stimulation of hair cells?

A

The fluid will go to the left at first. This doesn’t push the stereo cilia against the kinocilium. Therefore, this does NOT activate hair cells. Inhibitory effect.

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19
Q

T/F Some level of spontaneous firing of hair cells in vestibular apparatus will always go on.

A

True.

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20
Q

What is something different about the direction of the hair cells in the semicircular canals v. the utricle & saccule?

A

In the ampulla of the semicircular canals all of the hair cells are lined up in the same direction.
Not so in the otolithic organs. Here, they are lined up in both directions, symmetrical around a line called the striola.

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21
Q

What are the otoconia embedded in? What do they do?

A

embedded in otolithic membrane

when they move they get the hair cells to fire.

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22
Q

Describe the layers of the otolithic organs starting with the otoconia.

A 
Otoconia
Otolithic membrane (gelatinous)
Ends of Hair cells in the membrane, too. 
Reticular Membrane
Body of hair cells & supporting cells
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23
Q

T/F The cochlea is the posterior most portion of the entire apparatus.

A

FALSE. It is the most anterior part of the structure.

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24
Q

Describe the path of a vestibular nerve.

A

specialized receptors (hair cells) in semicircular canals, utricle, saccule send information.
nerves go to the vestibular ganglion.
After vestibular ganglion, vestibular nerve goes to inferior & medial vestibular nucleus. Synapse.
Ascend to the thalamus (VPL).
Go to the vestibular cortex (within the parietal sensory cortex).

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25
Q

What are the primary auditory nuclei?

A

ventral & dorsal cochlear nuclei

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26
Q

Which structure is a nice landmark to know that you are near the auditory & vestibular nuclei in the brainsteM?

A

inferior cerebellar peduncle

found near the pontomedullary jcn.

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27
Q

T/F The spinal tract V is the same as the inferior vestibular nucleus.

A

False. This is different. It only goes from the pons to the rostral spinal cord.

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28
Q

What are the vestibular nuclei especially important for?

A

important for balance & anti-gravity tone.

**the anti-gravity muscles contract when the utricle & saccule tell them to.

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29
Q

What are the 5 destinations that begin at the vestibular nuclei?

A
  1. Upper Spinal Cord
  2. Spinal Cord
  3. Cerebellum
  4. Parietal Sensory Cortex
  5. Brainstem Motor Nuclie
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30
Q

Describe the path from the vestibular nuclei–>upper spinal cord.

A

This is via the medial vestibulospinal tract.
This is a bilateral pathway.
It controls axial musculature for head & upper trunk rotation.

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31
Q

Describe the path from the vestibular nuclei–>spinal cord.

A

This is via the lateral vestibulospinal tract.
This is an ipsilateral pathway.
This controls the proximal anti-gravity muscles.

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32
Q

Describe the path from the vestibular nuclei to the parietal sensory cortex.

A

Goes to the thalamus (VPL).
Goes to the parietal sensory cortex (within this is the auditory cortex).
This helps plan movements based on position in space.

33
Q

Which brainstem motor nuclei are the vestibular nuclei connected to? What does this do?

A

Connected to the brainstem motor nuclei of CN3, 4, 6.
This controls VOR: coordinates eye movements with head movements.
VOR: vestibulocular reflex.

34
Q

Where are CN 7 & 8 found?

A

technically the pontomedullary jcn.

35
Q

When you fall & slip on the ice–>what is important to coordinate your movements?

A

medial & lateral vestibulospinal tracts

vestibulocerebellar tract too

36
Q

What are 2 important reflexes related to the vestibulospinal tracts & vestibulocerebellar tract?

A

VCR: vestibulo cervical reflex
VSR: vestibulo spinal reflex

37
Q

Once the medial longitudinal fascicles is below the brainstem it is considered what?

A

the medial vestibulospinal tract

38
Q

Ascending MLF is important for coordinating what?

A

eye movements

39
Q

The cerebellum modifies a lot of these descending pathways. Which part of the cerebellum do the medial & lateral vestibulospinal pathways end up @?

A

floculonodular lobe

40
Q

What are some important structures to consider when talking about VOR?

A

CN 3, 4, 6
PPRF nucleus
MLF tract

41
Q

Describe the ascending journey of MLF to control eye muscles.

A

Starts @ mid-pons
Ascends & crosses
Synapses in the midbrain @ the oculomotor nucleus w/ the oculomotor nerve.

42
Q

What does PPRF stand for?

A

paramedian pontine reticular formation

**the integrating nucleus for all signals.

43
Q

What is the reticular formation?

A

this is something that fills in the extra spaces where the columns stop

44
Q

If you look left…which muscles will be activated?

A

the abducens–>lateral rectus on left eye. The oculomotor–>medial rectus on right eye.

45
Q

What else synapses in the mid-pons, aside from MLF?

A

Abducens.

46
Q

What happens to your right semicircular canal if you turn your head right?

A

The fluid goes to the left.
Hair cells are excited (stereo move towards kino)
Vestibular Ganglion & Nerve excited
vestibular nuclei activated

47
Q

What happens to your right semicircular canal if you turn your head left?

A

The fluid goes right.
Hair cells are inhibited.
No transmission or firing to anything.

48
Q

Fluid movement towards/away the ampulla is excitatory.

A

Towards the ampulla is excitatory. Away is inhibitory.

49
Q

T/F Fluid can move all the way around a semicircular canal.

A

True.

50
Q

In VOR, if you move your head right, which direction do your eyes go?

A

Left

51
Q

Explain in detail the VOR if your head is moving right.

A

Head right
fluid left
Right semicircular canal activated
Left semicircular canal inhibited
Right crosses over @ PPRF & activates left abducens & right oculomotor.
Left lateral rectus & right medial rectus innervated.
You look left as a reflex.

52
Q

Your left/right brain talks to your left hand to move.

A

Right brain talks to the left hand.

53
Q

Describe how voluntary eye movement works if you are voluntarily looking to the left.

A

Right frontal eye field tells the eyes to look left.

Via left PPRF projection.

54
Q

If you get small lesions in your frontal eye fields–>what ability can you lose?

A

You can lose the ability to look in a direction voluntarily. But you can regain it eventually.

55
Q

What happens if you get a lesion to one vestibular nerve?

A

If you lose your left vestibular nerve, then your right one will be dominant (too much drive from PPRF from vestibular nuclei on one side). Your eyes will drift left & snap right. Called right nystagmus.

56
Q

What causes the snap back seen in nystagmus?

A

this is caused by cortical input, not brainstem.

Unconscious patients don’t have nystagmus, only drift.

57
Q

How can nystagmus be produced in normal patients?

A

rotate the subject

irrigating ears w/ hot or cold water (caloric nystagmus)

58
Q

What does COWS mean in terms of nystagmus?

A

Cold Opposite
Warm Same
**if you irrigate left ear w/ cold water, will see right nystagmus.
**If you irrigate left ear w/ warm water, will see left nystagmus.

59
Q

In unconscious patients, you don’t get the snap back of nystagmus. In a unconscious patient with an intact brainstem, you put cold water in right ear. Where is the slow drift?

A

Slow drift to the right.

60
Q

In a unconscious patient with an intact brainstem, you put warm water in right ear. Where is the slow drift?

A

Slow drift to the left.

61
Q

In a unconscious patient with a bilateral MLF lesion, you put cold water in right ear. Where is the slow drift?

A

Slow drift to the right.

62
Q

In a unconscious patient with a bilateral MLF lesion, you put warm water in right ear. Where is the slow drift?

A

Slow drift to the left.

63
Q

In an unconscious patient with a low brainstem lesion, you put cold water in right ear. Where is the slow drift?

A

No drift.

64
Q

In an unconscious patient with a low brainstem lesion, you put warm water in right ear. Where is the slow drift?

A

No drift.

65
Q

MLF lesions are common in which condition? What is this called?

A

common in MS

called internuclear ophthalmoplesia

66
Q

What happens in internuclear ophthalmoplesia?

A

when this happens the medial rectus muscle can’t be moved via the oculomotor nucleus.
then that eye can’t look inward.
can still converge for accomodation/near vision, though.
–this signal doesn’t come via 3 & 6 & PPRF

67
Q

T/F When you have internuclear ophthalmoplesia, your medial rectus muscle is paralyzed.

A

False. It isn’t paralyzed–>it can still work for accommodation. It just doesn’t work for looking inward via PPRF etc.

68
Q

Tell the story of a right eye MLF lesion.

A

You try to drive your eyes left voluntarily.
Lateral rectus works properly.
Left eyes looks left via lateral rectus.
Right eye stays midline b/c the medial rectus isn’t signaled properly.
Left eye gets lonely b/c it doesn’t have a buddy…it snaps back to the midline. Dissociated right nystagmus.

69
Q

What happens with a left vestibular lesion?

A

the right eye is then dominant.
right eye drifts left & then snaps right.
right nystagmus

70
Q

What happens with a left PPRF lesion?

A

Right eye dominant.
Eye drifts slowly right.
Snaps left.
Left nystagmus.

71
Q

What happens with a left abducens nucleus lesion? Is this upper or lower motor neuron damage?

A

get atrophy & paralysis of the left lateral rectus muscle
-lower motor neuron damage
ALSO…
get damage to the part that talks to the oculomotor nucleus & medial rectus won’t move (not paralyzed tho).
-upper motor neuron damage

72
Q

So…if you have a left abducens nucleus lesion & you tell your left eye to move…what will it do?

A

It just won’t move.

73
Q

What makes a lower motor neuron lesion?

A

lesion to the neuron that directly innervates the muscle

74
Q

What makes an upper motor neuron lesion?

A

lesion to the neuron that talks to the neuron that directly innervates the muscle.

75
Q

What happens if you get a lesion to the abducens nerve (not the nucleus)? How likely is this type of lesion to happen?

A

pretty possible–>b/c the CN6 is susceptible to damage in the cranial cavity b/c of its long course.
you try to move your left eye left & it won’t b/c lateral rectus paralyzed
the right eye can look left, tho. Medial rectus not damaged.
Get double vision.
Get nystagmus.

76
Q

Review:
Abducens Nucleus Lesion. Lower or upper motor neuron damage? Double vision?
Abducens Nerve Lesion. Lower or upper motor neuron damage? Double Vision?

A

Abducens Nucleus: Lower & upper; no double vision

Abducens Nerve: Lower. Double vision.

77
Q

How might a pt with a left abducens nerve lesion position himself?

A

He won’t want to see w/ double vision.
He won’t be able to look left w/o experiencing double vision. So instead, he will try to put the right side of his body out to the world & look right. This side works.

78
Q

If you see someone positioning themselves to always look right to avoid double vision…you could think left abducens damage or you could think what?

A

Right medial rectus damage w/o abducens damage.

Block 5; Week 2 (8 decks)

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