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Anatomy 2 Unit 3 > 5 - Auditory and Vestibular System > Flashcards

5 - Auditory and Vestibular System Flashcards

1
Q

The auditory and vestibular receptors innervated by the vestibulocochlear nerve are located within the

A

petrous part of the temporal bone. Within the temporal bone is space (bony tube) that suspends a membranous tube.

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2
Q

Perilymph: Fills

A

perilymphatic space (between bony and membranous labyrinths)

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3
Q

Perilymph: Similar to

A

extracellular fluid

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4
Q

Perilymph: Continuous with

A

subarachnoid space through the cochlear aqueduct

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5
Q

Endolymph

A

Fills membranous labyrinth
Continuous throughout
Closed system
Similar to intracellular fluid

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6
Q

Cells within the walls of the membranous labyrinth are connected by

A

tight junctions creating a diffusion barrier

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7
Q

There is a redox differential between

A

inside out outside of cells and this is reminiscent of potential difference across the membranous labyrinth. What I mean by this is that the intracellular fluid is more negative and the intercellular fluid. More negative charge in biology means a more reduced environment and more positive charge means a more oxidized environment. This allows for depolarization to occur if ion channels are opened and the potential different can be reduced through the flow of ions.

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8
Q

Endolymph is secreted by cells within the

A

cochlea called stria vascularis (and other locations)

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9
Q

Endolymph flows out through the

A

endolymphatic duct to the endolymphatic sac where it is reabsorbed

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10
Q

Endolymph production this process is reminiscent of

A

CSF secretion and reabsorption.

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11
Q

The endolymphatic sac is located within the

A

dura of the temporal bone and is the site of reabsorption.

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12
Q

Blockage can result in swelling of the

A

membranous labyrinth (endolymphatic hydrops), which is thought to be a cause of Ménière’s disease (tinnitus, transient attacks of vertigo, nausea & hearing loss).

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13
Q

Auditory and Vestibular Receptors are

A

Hair Cells

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14
Q

Hair cells are within the

A

membranous labyrinth

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15
Q

Hair cell Stereocilia project into the

A

endolymph (apical projections)

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16
Q

Hair cell Basal surface synapses with

A

peripheral processes with CN VIII (both divisions)  CNS

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17
Q

Hair cell Stereocilia arranged in

A

rows (tallest is kinocilium, but only found in vestibular portions)

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18
Q

Groups of hair cells, tallest stereocilia project into a

A

gelatinous mass

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19
Q

Hair cells are

A

mechanosensitive transduction channels

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20
Q

Stereocilia are

A

rigid (actin)

Bend at the base

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21
Q

Stereocilia are

A

linked to each other

Bend as a unit

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22
Q

Tip Links at the tips up towards the

A

tallest neighbor

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23
Q

Deflect towards tallest stereocilia

A

stretches tip links and depolarizes the hair cell  firing of CN VIII fibers

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24
Q

Deflection towards the tallest stereocilia =

A

depolarize hair cell.

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25
Q

Deflection away from tallest stereocilia =

A

hyperpolarize hair cell.

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26
Q

Deflection in a perpendicular direction =

A

no response.

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27
Q

Subtle differences in the physical arrangements of hair cells determine the

A

stimuli to which they are most sensitive

Cochlea, Vestibule & Semicircular Canals use the same general mechanism

Coupling of gelatinous masses and stereocilia

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28
Q

Arrangement is key to the type of

A

signal that gets transduced
Sound (cochlea)
Head movement (semicircular ducts)
Head position (utricle & saccule)

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29
Q

Cochlear Division Overview

A

Conveys information about sound
Organ of Corti (auditory receptor organ)
Outer ear & Middle ear = air filled
Inner ear = liquid filled

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30
Q

The job of the outer and middle ears is to

A

transfer sound efficiently through the air: liquid interface into the inner ear.

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31
Q

The job of the outer and middle ears is to

A

transfer sound efficiently through the air: liquid interface into the inner ear.

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32
Q

Remember: membrane suspended in

A

perilymph and filled with endolymph

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33
Q

Cochlea = bone, forms

A

2¾ turns

Modiolus with Osseous Spiral Lamina

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34
Q

The cochlear duct is

A

triangular in cross section, each of the walls has different name and function.

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35
Q

Sounds travels from the vestibule into the

A

scala vestibule  helicotrema (apex)  scala tympani  round window membrane.

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36
Q

Direction of sound movement through perilymph

A

This movement will slightly deform the cochlear duct and will stimulate cells within it.

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37
Q

Traveling waves in the basilar membrane stimulate hair cells in the

A

Organ of Corti, in locations that depend of sound frequency

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38
Q

Intensity  determined by the

A

rate and number of nerves firing

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39
Q

Frequency 

A

Basilar membrane & Organ of Corti (tonotopic organization)

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40
Q

Location  accomplished by comparing

A

stimuli between ears within the CNS

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41
Q

Organ of Corti: Hair cells sit on the

A

basilar membrane
Inner hair cells: X tectorial membrane
Outer hair cells: ✓ tectorial membrane

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42
Q

Organ of Corti: Basilar membrane

A

Stiff at the base, responds to high frequencies

Floppy at the apex, responds to low frequencies

43
Q

Organ of Corti: Tonotopic organization maintained within

A

CNS

44
Q

Cochlear Implants

A

Take advantage of tonotopic organization of cochlea
Used when cochlear hair cells damaged, but VIII endings are intact

Place electrodes in round window into scala tympani so different electrodes are placed at different points along basilar membrane

Electronics stimulate VIII endings at appropriate tonotopic levels

45
Q

Primary afferents stimulated by hair cells contain their cell bodies in

A

spiral ganglion and synapse at both the dorsal cochlear nucleus and the ventral cochlear nucleus.

46
Q

Both nuclei project

A

bilaterally. Second order fibers from the dorsal cochlear nucleus ascend in the lateral lemniscus.

47
Q

Second order fibers from the ventral cochlear nucleus synapse at the

A

superior olivary nucleus (which is involved in sound localization) by crossing through the trapezoid body, then fibers from the superior olivary nucleus ascend through the lateral lemniscus.

48
Q

The lateral lemniscus terminates at the

A

inferior colliculus.

49
Q

The inferior colliculus then sends fibers through the

A

inferior brachium to the medial geniculate nucleus (MGN) of the thalamus.

50
Q

The MGN then projects to the

A

transverse temporal gyri, which is the primary auditory cortex, located on the superior aspect of the temporal lobe.

51
Q

The inferior brachium is also called the

A

brachium of the inferior colliculus.

52
Q

Main functions of the vestibular system:

A

Regulate posture (an example is the Erector Spinae muscles)
Coordinate eye movements
Coordinate head movements

53
Q

Vestibular Division : Bony portion

A

1 Vestibule

3 Semicircular canals

54
Q

Vestibular Division Membranous portion

A

2 otolithic organs (saccule & utricle)

3 Semicircular ducts

55
Q

Each semicircular duct has an dilation called an

A

ampulla, containing several structures:

56
Q

Crista

A 
Supporting cells
Hair cells (unidirectional per semicircular duct)
57
Q

Cupula (gelatinous mass)

Creates a

A

partition across the ampulla
Responds to angular acceleration
Deflection in perpendicular direction (like turning a wheel) will either increase or decrease firing rate of afferents
The 3 ducts are arranged so rotation be detected from all three dimensional planes

58
Q

The semicircular ducts are not able to detect

A

continuous rotation

59
Q

Because of inertia the endolymph initially

A

lags behind (meaning it takes longer to accelerate up to speed) it results in a deflection of the cupula. But with constant rotation the endolymph catches up and the cupula is no longer deflected and the stimulus cannot be detected. Although, think about it, how often are you in situations where you experience constant rotation. This may occur on a roller coaster, but is very rare.

60
Q

The utricle and saccule each have a tuft of hair cells called the

A

macula

61
Q

The stereocilia (and kinocilium) project into a

A

gelatinous mass called the otolithic membrane

62
Q

The otolithic membrane flops in response to

A

various positions of the head and stays flopped in order to indicate head position in response to linear accelerations

63
Q

The otolithic membrane contains small bits of

A

calcium carbonate called otoconia (ear sand or ear stones).

64
Q

The most common form of linear acceleration that we experience is

A

gravity, but we also experience linear accelerations in elevators and cars.

65
Q

Utricle –>

A

forward/backward & side/side

66
Q

Saccule –>

A

forward/backward & up/down

67
Q

Hair cells stimulate the

A

peripheral processes of the vestibular division of CN VIII

68
Q

Vestibular ganglion projects directly the

A

cerebellum (via the juxtarestiform body) & the vestibular nuclei

69
Q

There are 4 vestibular nuclei within the vestibular nuclear complex on each side

A

Inferior
Medial
Lateral
Superior

70
Q

The vestibular nuclei have a particular pattern of connections with the

A

semicircular canals, utricle & saccule, but they will all here treated as one continuous complex here.

71
Q

Cerebellum

Directly from the

A

flocculonodular lobe

72
Q

Spinal cord

Directly from

A

spinovestibular fibers

73
Q

Visual information

Indirectly from

A

various nuclei in the brainstem

To distinguish between movement and just movement across the retina

74
Q

Contralateral vestibular nuclei

A

Extensively interconnected

75
Q

Vestibular nuclei: Spinal cord

A

Regulate posture

76
Q

Vestibular nuclei: Cerebellum

A

Coordinate head movements

77
Q

Vestibular nuclei: Nuclei of CN III, IV & VI

A

Coordinate eye movements

78
Q

Vestibular nuclei: Thalamus–> Cerebral cortex

A

Conscious awareness

79
Q

Vestibular nuclei: Visceral nuclei

A

Autonomic effects

80
Q

Some of the autonomic effects can be things such as

A

cardiovascular adjustments or seasickness.

81
Q

Some of the autonomic effects can be things such as

A

cardiovascular adjustments or seasickness.

82
Q

Lateral vestibulospinal tract

A

Stabilize posture
Lateral vestibular nucleus  runs next to spinothalamic tract  antigravity muscles at all spinal levels
Stays ipsilateral

83
Q

Medial vestibulospinal tract

A

Stabilize head (from walking & eye movements)
Medial vestibular nucleus  MLF  cervical spinal cord
Bilateral

84
Q

Vestibuloocular reflex

A

Generate eye movements that compensate for head movements, this keeps the eye fixed on an object in the visual field
Retinal photoreceptors are slow
Semicircular canals  vestibular nuclei  MLF & RF  nuclei of CN III, IV & VI
Afferent limb = CN VIII
Efferent limb = Nuclei that control the extraocular muscles
Interneuronal connects = MLF & RF

85
Q

Nystagmus: Physiological

A

Aid in keeping images on the retina during movement
Slow period
Fast period, “reset” movement

can also be pathological

86
Q

Cupula and gravity: Normally the cupula has the same

A

density as the surrounding endolymph so it is not deflected by gravity

87
Q

Excessive alcohol consumption

A

Alcohol penetrates inner ear

88
Q

Dislodged otoconia

A

“plunger effect”

89
Q

Position Sense

A 
They all work together:
Vestibular sense
Proprioceptive sense
Visual sense
Need 2 out of 3 to be functioning for adequate day to day life
Loss of 2 or 3 is disabling
Rhomberg’s sign
90
Q

tympanic membrane from

A

first pharyngeal cleft and groove

ectoderm and endoderm (internal is endoderm)

91
Q

Tensor tympani attached to

A

handle of maleus

92
Q

Muscles of pharyngotympanic tube

A

levator palatini along axis of tube

tensor veli palatini comes up 90 degrees to tube, attaches to cartilage and membranous portion and opens tube.

93
Q

tegmen tympani

A

roof of middle ear

94
Q

manubrium of maleus attached to

A

tympanic membrane

95
Q

Promentory

A

medial wall - protuberance from cochlea

96
Q

facial canal prominence created by

A

cn VII

97
Q

Anterior part of maleus

A

anchor and stabilizer

98
Q

Tensor tympani

A

V3

derived from pharyngeal arch 1

99
Q

Tensor veli palatini

A

VII

Arch 2

100
Q

chorda tympani

A

passes between maleus and incus

101
Q

tympanic plexus on surface of

A

promentory

102
Q

Inner ear enclosed in

A

petrous ridge of temp boen

103
Q

Helicotrema

A

where scala tympani and vestibuli connect - lymph goes around, through this, and back around.

104
Q

Perilymph has a more

A

positive charge, endolymph the opposite.

Anatomy 2 Unit 3 (14 decks)

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