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

5 - Auditory and Vestibular System Flashcards

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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
Deflection away from tallest stereocilia =
hyperpolarize hair cell.
26
Deflection in a perpendicular direction =
no response.
27
Subtle differences in the physical arrangements of hair cells determine the
stimuli to which they are most sensitive Cochlea, Vestibule & Semicircular Canals use the same general mechanism Coupling of gelatinous masses and stereocilia
28
Arrangement is key to the type of
signal that gets transduced Sound (cochlea) Head movement (semicircular ducts) Head position (utricle & saccule)
29
Cochlear Division Overview
Conveys information about sound Organ of Corti (auditory receptor organ) Outer ear & Middle ear = air filled Inner ear = liquid filled
30
The job of the outer and middle ears is to
transfer sound efficiently through the air: liquid interface into the inner ear.
31
The job of the outer and middle ears is to
transfer sound efficiently through the air: liquid interface into the inner ear.
32
Remember: membrane suspended in
perilymph and filled with endolymph
33
Cochlea = bone, forms
2¾ turns Modiolus with Osseous Spiral Lamina
34
The cochlear duct is
triangular in cross section, each of the walls has different name and function.
35
Sounds travels from the vestibule into the
scala vestibule  helicotrema (apex)  scala tympani  round window membrane.
36
Direction of sound movement through perilymph
This movement will slightly deform the cochlear duct and will stimulate cells within it.
37
Traveling waves in the basilar membrane stimulate hair cells in the
Organ of Corti, in locations that depend of sound frequency
38
Intensity  determined by the
rate and number of nerves firing
39
Frequency 
Basilar membrane & Organ of Corti (tonotopic organization)
40
Location  accomplished by comparing
stimuli between ears within the CNS
41
Organ of Corti: Hair cells sit on the
basilar membrane Inner hair cells: X tectorial membrane Outer hair cells: ✓ tectorial membrane
42
Organ of Corti: Basilar membrane
Stiff at the base, responds to high frequencies | Floppy at the apex, responds to low frequencies
43
Organ of Corti: Tonotopic organization maintained within
CNS
44
Cochlear Implants
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
Primary afferents stimulated by hair cells contain their cell bodies in
spiral ganglion and synapse at both the dorsal cochlear nucleus and the ventral cochlear nucleus.
46
Both nuclei project
bilaterally. Second order fibers from the dorsal cochlear nucleus ascend in the lateral lemniscus.
47
Second order fibers from the ventral cochlear nucleus synapse at the
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
The lateral lemniscus terminates at the
inferior colliculus.
49
The inferior colliculus then sends fibers through the
inferior brachium to the medial geniculate nucleus (MGN) of the thalamus.
50
The MGN then projects to the
transverse temporal gyri, which is the primary auditory cortex, located on the superior aspect of the temporal lobe.
51
The inferior brachium is also called the
brachium of the inferior colliculus.
52
Main functions of the vestibular system:
Regulate posture (an example is the Erector Spinae muscles) Coordinate eye movements Coordinate head movements
53
Vestibular Division : Bony portion
1 Vestibule | 3 Semicircular canals
54
Vestibular Division Membranous portion
2 otolithic organs (saccule & utricle) | 3 Semicircular ducts
55
Each semicircular duct has an dilation called an
ampulla, containing several structures:
56
Crista
``` Supporting cells Hair cells (unidirectional per semicircular duct) ```
57
Cupula (gelatinous mass) | Creates 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
The semicircular ducts are not able to detect
continuous rotation
59
Because of inertia the endolymph initially
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
The utricle and saccule each have a tuft of hair cells called the
macula
61
The stereocilia (and kinocilium) project into a
gelatinous mass called the otolithic membrane
62
The otolithic membrane flops in response to
various positions of the head and stays flopped in order to indicate head position in response to linear accelerations
63
The otolithic membrane contains small bits of
calcium carbonate called otoconia (ear sand or ear stones).
64
The most common form of linear acceleration that we experience is
gravity, but we also experience linear accelerations in elevators and cars.
65
Utricle -->
forward/backward & side/side
66
Saccule -->
forward/backward & up/down
67
Hair cells stimulate the
peripheral processes of the vestibular division of CN VIII
68
Vestibular ganglion projects directly the
cerebellum (via the juxtarestiform body) & the vestibular nuclei
69
There are 4 vestibular nuclei within the vestibular nuclear complex on each side
Inferior Medial Lateral Superior
70
The vestibular nuclei have a particular pattern of connections with the
semicircular canals, utricle & saccule, but they will all here treated as one continuous complex here.
71
Cerebellum | Directly from the
flocculonodular lobe
72
Spinal cord | Directly from
spinovestibular fibers
73
Visual information | Indirectly from
various nuclei in the brainstem | To distinguish between movement and just movement across the retina
74
Contralateral vestibular nuclei
Extensively interconnected
75
Vestibular nuclei: Spinal cord
Regulate posture
76
Vestibular nuclei: Cerebellum
Coordinate head movements
77
Vestibular nuclei: Nuclei of CN III, IV & VI
Coordinate eye movements
78
Vestibular nuclei: Thalamus--> Cerebral cortex
Conscious awareness
79
Vestibular nuclei: Visceral nuclei
Autonomic effects
80
Some of the autonomic effects can be things such as
cardiovascular adjustments or seasickness.
81
Some of the autonomic effects can be things such as
cardiovascular adjustments or seasickness.
82
Lateral vestibulospinal tract
Stabilize posture Lateral vestibular nucleus  runs next to spinothalamic tract  antigravity muscles at all spinal levels Stays ipsilateral
83
Medial vestibulospinal tract
Stabilize head (from walking & eye movements) Medial vestibular nucleus  MLF  cervical spinal cord Bilateral
84
Vestibuloocular reflex
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
Nystagmus: Physiological
Aid in keeping images on the retina during movement Slow period Fast period, “reset” movement can also be pathological
86
Cupula and gravity: Normally the cupula has the same
density as the surrounding endolymph so it is not deflected by gravity
87
Excessive alcohol consumption
Alcohol penetrates inner ear
88
Dislodged otoconia
“plunger effect”
89
Position Sense
``` 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
tympanic membrane from
first pharyngeal cleft and groove ectoderm and endoderm (internal is endoderm)
91
Tensor tympani attached to
handle of maleus
92
Muscles of pharyngotympanic tube
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
tegmen tympani
roof of middle ear
94
manubrium of maleus attached to
tympanic membrane
95
Promentory
medial wall - protuberance from cochlea
96
facial canal prominence created by
cn VII
97
Anterior part of maleus
anchor and stabilizer
98
Tensor tympani
V3 | derived from pharyngeal arch 1
99
Tensor veli palatini
VII | Arch 2
100
chorda tympani
passes between maleus and incus
101
tympanic plexus on surface of
promentory
102
Inner ear enclosed in
petrous ridge of temp boen
103
Helicotrema
where scala tympani and vestibuli connect - lymph goes around, through this, and back around.
104
Perilymph has a more
positive charge, endolymph the opposite.

Anatomy 2 Unit 3 (14 decks)

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