L8: Auditory Senses Flashcards

1
Q

conduction pathway sequence of the ear

A

tympanic membrane
ossicles
oval window

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2
Q

auditory ossicles

A

malleus
incus
stapes

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3
Q

malleus

A

attaches tympanic memb to incus

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4
Q

incus

A

intermediate bone between malleus and stapes

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5
Q

stapes

A

stirrup shape for stapedial artery to pass

connects incus to oval window

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6
Q

openings of the middle ear

A

oval window

round window

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7
Q

oval window

A

opens into the scala vestibuli

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8
Q

round window

A

a membrane covered window at the end of the scala tympani

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9
Q

muscles of the middle ear

A

tensor tympani

stapedius

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10
Q

tensor tympani

A

inserts on the malleus

pulls handle of malleus inward

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11
Q

stapedius

A

inserts on the stapes and pulls it outward

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12
Q

function of middle ear muscles

A

contract reflexively in response to loud sounds

in order to dampen the vibrations

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13
Q

impedance matching

A

tympanic memb is 17x smaller than stapes surface area

this increases the force from ossicular lever system to cochlear by 22x

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14
Q

importance of impedance

A

fluid has greater inertia than air and thus requires this increase in force in order to create vibration in fluid

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15
Q

who provides impedance

A

tympanic memb and ossicles

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16
Q

cochlea components

A

3 side by side coiled tubes

scala vestibuli, media, tympani

and reissner’s memb also called vestibular memb

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17
Q

what does reissner’s membrane separate?

A

scala media from scala vestibuli

18
Q

explain width of reissner’s membrane

A

is so thin that the scala media and vestibuli are considered a single chamber when discussing sound

19
Q

purpose of reissner’s membrane

A

keeps special fluid w/in scala media

20
Q

what does the basilar membrane separate

A

scala media from scala tympani

21
Q

trace basilar membrane fibers

A

project from modiolus of cochlea outer wall
to
basilar membrane

but the distal fiber ends are not fixed

these fibers can vibrate

22
Q

function of basilar fibers

A

transfer vibrations

stiff short fibers near oval window = higher frequency

long limber fibers near apex of cochlea = low frequency of vibration

23
Q

function of organ of corti

A

generates nerve impulses in response to vibration of basilar membrane

24
Q

sensory receptors of organ of corti

A

hair cells
single row of internal cells
3-4 rows of external cells

25
contents of scala media and tympani
endolymph perilymph
26
hair cell stimulation
stim nerve fibers that lead to the spiral ganglion of corti
27
how do hair cells transmit signals
stereocilia of hair cells touch or embed in tectorial memb bending of the hair cells = depolarization bending in opposite direction = hyperpolarization
28
outer ends of hair cells are tightly attached to ?
reticular lamina supported by rods of corti which are attached to basilar fibers thus creating a rigid unit
29
axons of neurons in the ganglion
axons are sent to upper medulla via cochlear nerve | CN VIII
30
basilar fibers length increases from ?
oval window to apex of cochlea
31
diameter of basilar fibers decrease from ?
oval window to apex of cochlea
32
mvt of basilar fibers causes mvt of _________ , which causes shearing forces on _______ against the _______________. thus whenever basilar membrane moves ?
reticular lamina hair cells tectorial memb hair cells become excited
33
hair cell stereocilia
about 100 on their apical border are longer on side farther from modiolus
34
depolarization of hair cells
occurs when cilia are bent towards longer ones a tensile force is created on shorter ones creates mechanical transduction that opens K channels
35
endolymph
high K conc low Na conc + charge = endocochlear potential
36
voltage potential of endo/peri-lymph
+80 difference between them scala media is + = endocochlear potential
37
tops of hair cells project thru ?
the reticular lamina | thus bathed in endolymph
38
lower bodies of hair cells
surrounded by perilymph
39
intracellular potential of hair cells
- 150 apical ends in endolymph | - 70 lower bodies in perilymph
40
place principle
nervous system detects sound frequencies by determining positions along the basilar memb that are most stimulated
41
6 components of the nervous system pathway for sound
1. spiral organ of corti 2. dorsal n ventral cochlear nuclei 3. superior olivary nucleus 4. lat lemniscus nucleus 5. med geniculate nucleus (in the thalamus) 6. auditory cortex
42
auditory cortex
located in temporal lobe | dif areas associated w/ high vs low sound frequencies