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Physiology > Section 3 Vestibular System > Flashcards

Section 3 Vestibular System Flashcards

1
Q

Vestibular fxns:

A

stabilization of eye position, perc of body rotation and translation, visual and postural vertical perc

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2
Q

Disorders of the vestibular system:

A

Meniere’s disease, Benign Paroxysmal Positional Vertigo (BPPV)

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3
Q

BPPV is more common as:

A

you age

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4
Q

What signal the static position of the head with respect to gravity and its linear acceleration?

A

Utricle and saccule

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5
Q

What signals rotation and angular acceleration of the head?

A

Semicircular canal

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6
Q

Names of the 3 loops of the semicircular canal:

A

ant, pos, and lateral

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7
Q

What regions of the ear contain hair cells?

A

Cochlea? (check)

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8
Q

The utricle detects:

A

linear accelerations and head-tilts in the horizontal plane.

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9
Q

The saccule detects:

A

linear accelerations and head-tilts in the vertical plane.

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10
Q

Where are the axons of the utricle located?

A

Trick Question. There are none

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11
Q

Explain the transmission of info from the hair cell in the utricle.

A

Synaptic vesicles in body of hair cell release glutamate on 8th nerve afferents which send info about these organs to the brain

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12
Q

How many 8th nerve afferents are connected to each hair cell?

A

1 in the images in slides

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13
Q

At which end of the hair cells are the hair bundles?

A

Apical end

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14
Q

What are the tips of the hair cells embedded in?

A

Otolithic membrane, gelatinous structure overlying the hair cells

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15
Q

Fxn of otoconia:

A

to add extra weight to the structure

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16
Q

What are found on the otolithic membranes in the utricle?

A

Otoconia (Ca carbonate crystals)

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17
Q

Endolymph has a high conc of what ion?

A

K+, positively charged

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18
Q

What are the hair bundles surrounded by?

A

endolymph

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19
Q

2 different ECF involved w hair cells:

A

Endolymph, high K+ and positively charged (top of the structure) and perilymph, high Na++ and low K+, surrounding the hair cell bodies

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20
Q

Effects of tilting head:

A

tilt membrane that is mechanically coupled to the bone that surrounds the structure

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21
Q

What causes distortion of the otolithic membrane?

A

weight of the otoconia when tilting head

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22
Q

Linear acceleration:

A

distortion of the hair cell with respect to body, epi moves in same direction as head bc they are mechanically connected, bending of the hair bundles

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23
Q

What causes the hair uncles to bend during acceleration?

A

the inertia of the heavy crystals that accelerate more slowly than the hair cell bodies

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24
Q

How many kinocilium per hair strucutre are there?

A

1

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25
Q

Kinocilium is aka:

A

true cilium

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26
Q

Where are kinocilium located?

A

all vestibular hair cells

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27
Q

How are the hair stereocilia arranged?

A

Same height L to R - polarized, short to tall in other direction, affects how each of the hair cells work

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28
Q

Fxn of step-like arrangement of stereocilia of the hair cell:

A

How moves of upper part of structure triggers electrical changes to go to the CNS (check)

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29
Q

About how many stereocillia are there?

A

60

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30
Q

What system is the kinocilium related to:

A

vestibular

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31
Q

How are the stereocilia arranged?

A

Step-like

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32
Q

How are adjacent stereocilia of the hair cell attached?

A

Tip links

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33
Q

Where do tip-links attach to the stereocilia?

A

locations of mecahno receptor channels

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34
Q

Fluid bathing the stereocilia:

A

endolymph, K+ is the predominant ion that will be flowing in (Ca as well, but mainly K)

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35
Q

What 2 ions can flow into the stereocilia?

A

Ca and K

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36
Q

What is the extracellular fluid of the inner ear?

A

endolymph

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37
Q

Disorders of the endolymph:

A

disruption of endolymph production or hair cells fxn

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38
Q

Disruption of endolymph production can lead to:

A

Vertigo, vomiting, hearing impairment

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39
Q

What can cause the disruption of endolymph production?

A

inflammation of the inner ear

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40
Q

Meniere’s disease:

A

disruption of the hair cell fxn, attacks w no warning, last hours

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41
Q

Possible causes of Meniere’s disease:

A

head trauma, virus, or rise in endolymph volume due to hole in membrane separating endolymph and cochlea fluids OR improper endolymph drainage

42
Q

What is the hair cell potential?

A

-50mV, bc cell is slightly depolarized due to the tugging on membrane that open mechanoreceps allowing K to enter

43
Q

How do the hair cells activate its afferents?

A

NTs

44
Q

When will there be no volvtage change in hair cell receps?

A

Orthogonal (R angle) tilt

45
Q

When is the 8th nerve firing rate at its greatest?

A

When the hair fibers are flowing in the opposite direction of the 8th nerve., largest space bw stereocilia opening more channels

46
Q

When is the 8th nerve firing rate at its least?

A

hair fibers tilted in direction of the 8th n.

47
Q

How is the 8th n. firing when there is no movement of the hair cell?

A

active signal that says that nothing much is happening

48
Q

How can direction be conveyed via the hair cells. How do the cells transmit this info differently?

A

When not moving there is an intermediate firing rate, when pushed in either direction the firing rate will either increase or decrease making directional differentiation easy

49
Q

Firing rate of a hair cell at rest:

A

100 Hz

50
Q

What NT is used by the hair cells to transmit info?

A

glutamate

51
Q

How are the tip links connected in the orthogonal directon (into the plane of the page)?

A

They aren’t

52
Q

The utricle can detect head tilt in any direction away from:

A

vertical

53
Q

How are the hair cells at different angles in the utricle affected with a tilt of the head?

A

some depolarize, some hyperpolarize, some not affected

54
Q

T or F? Hair cells are more sensitive in one direction.

A

T.

55
Q

What structure looks just like the utricle but is oriented vertically in the upright head?

A

Saccule

56
Q

When does the sacculus sense most effectively?

A

When the head is on its side

57
Q

What do the semicircular canals respond to?

A

Head rotation

58
Q

How many canals are there on each side?

A

3: 1 horizontal (L R turning of head), 1 ant and 1 pos duct, both upright, 90’ to each other (X,Y,Z axis)

59
Q

T or F? Semicircular canals respond to linear and static tilt.

A

F. head rotation only

60
Q

Specialized region that contains hair cells:

A

ampulla

61
Q

Hair bundles that stick out are assoc w:

A

cupula (flexible)

62
Q

What allows for endolymph to participate in the signaling of changes in movement?

A

it is fluid and not mechanically coupled to the outside structures (i.e. the cupola is coupled to membrane)

63
Q

What bends in the endolymph with moves?

A

cupula

64
Q

A turn to the R depolarizes all the hair cells in the:

A

R horizontal canal

65
Q

In which manner are movements of variable speed transmitted?

A

in a graded manner

66
Q

T or F? A turn to the R depolarizes ALL the hair cells in the R horizontal canal.

A

T

67
Q

This/these structure(s) has hair bundles of only one orientation while this/these structure(s) have hair bundles oriented in all directions.

A

semicircular canal, saccule and utricle

68
Q

Where are the larger stereocilia located?

A

toward the back of the head

69
Q

When you turn your head to the R will the tip links in the L canal be brought closer together or spread further apart?

A

closer

70
Q

When you turn your head to the R will more or less K enter the cilia of the L canal? More or less firing?

A

less K coming in, less positive charge, and less firing

71
Q

Turn head to the R:

A

L horiz canal hyperpol, R horiz canal dep

72
Q

Turn head to the L:

A

L horiz canal depol, R horiz canal hyperpol

73
Q

What will the 8th n. afferent increase or decrease its firing rate in response to?

A

direction and rate of motion

74
Q

What does redundancy of info from the 2 sides allow for?

A

vestibular compensation

75
Q

2 clases of symptoms related to damage to vestibular canals, otoliths, and/or vestibular n. on one side of the head:

A

static (seen in absence of head moves) and dynamic (seen w head moves)

76
Q

T or F? Peripheral damage to the vestibular system can be compensated for.

A

T

77
Q

Immediate effects of damage to vestibular canals, otoliths, and/or vestibular n. on one side of the head:

A

problems w balance, posture, gait, and eye moves

78
Q

T or F? There is a quick recovery time with vestibular compensation.

A

F. gradual

79
Q

T or F? Different symptoms of vestibular compensation recover at different rates.

A

T

80
Q

Example of when vestibular compensation is important:

A

when there are more subtle changes in vestibular input such as a loss of a few hair cells

81
Q

Likely sites for where compensation occurs:

A

vestibular nuclei and cerebellum

82
Q

What fraction of the hair cells die off with aging?

A

About 1/4

83
Q

Faction of adults, 65+ that fall each year:

A

1/3

84
Q

Leading cause of injury or death for people 65+:

A

falls

85
Q

vestibular issue that rises in frequency in the 40’s:

A

bening parxysmal position vertigo (BPPV)

86
Q

Cause of BPPV:

A

detachment of otoconia in the utricle, allowing them to enter a semicircular duct

87
Q

What causes a person w BPPV to feel like they are spinning?

A

lodging of Ca carbonate crystal in a position that causes them to incorrectly activate hair cells of the semicircular canal

88
Q

Tx for BPPV:

A

Otolith Repositioning Procedure

89
Q

When does severe vertigo occur for pts with BPPV?

A

head moves

90
Q

How is vestibular info distributed?

A

Widely in the thalamus

91
Q

Vestibular info can combined with (what?) to maintain balance.

A

visual and proprioceptive input

92
Q

What sort of visual and proprioceptive input does the thalamus receive?

A

visual response to optokinetic stimuli (large field, moving stimuli) and prop to neck m. moves

93
Q

Large-field, moving stimuli:

A

Optokinetic stimuli

94
Q

Somatosensory lesion:

A

sensation that vertical objects are tilted toward the side of the lesion

95
Q

What do cells in the somatosensory cortex respond to?

A

some cell: head rotation, others: head tilt

96
Q

What is the most common sensation in the cortical vestibular responsive areas?

A

rotation

97
Q

T or F? There are only a couple of areas of the brain yielding vestibular sensations.

A

F many areas

98
Q

Major vestibular area (concentration) in the cortex:

A

temporo-parietal and parietoinsular cortex

99
Q

T or F? Some cells in the cortical vestibular responsive areas have a purely vestibular response.

A

T. Others are multimodal (visual, prop, vestibular)

100
Q

posterior T cortical lesions:

A

impair vestibular-derived saccades

101
Q

Insulotemporal infarctions may lead to:

A

a tilted perception of visual vertical and to rotational vertigo in stroke pts

102
Q

What does an impairment of eye responses indicate?

A

vestibular signal not working correctly

Physiology (55 decks)

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