Ch. 53 Hearing Flashcards

1
Q

Conduction of sound pathway

A

tympanic membrane –>ossicles–>chochlea

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2
Q

tympanic membrane is attached to the

A

handle of the malleus

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3
Q

3 bones in middle ear:

A
  1. malleus
  2. incus
  3. stapes (connects to oval window –>inner ear)
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4
Q

Attenuation of sound:

A

after 40-80 seconds of intense sound:
1. stapedius uscle
2. tensor tympani mucles
are contracted with increased rigitidy in ossicles = reduces sound conduction

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5
Q

Attenuation of sound benefits (3)

A
  1. protect cohlea from damaging vibration
  2. masks low frequency sounds in environments
  3. decreases hearing sensitivity to own speech
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6
Q

Transmissin of sound through bone

A

Cochlea implanted in temporal bone. Vibration enter skull = fluid vibrations in chochlea

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7
Q

Cochlea is made of:

A

3 tubes coiled side by side:
1. scala vestibuli
2. scala media
3. scala tympani

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8
Q

Sound vibration pathway

A

vibrations–>scala vestibuli via faceplate at oval window –>faceplate moves inward to push fluid forward and outward to move fluid backward

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9
Q

Stiff, short fibers are near

A

oval window

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10
Q

stiff, short fibers beat at

A

very high frequency

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11
Q

long, limber fibers are near

A

tip of cochlea

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12
Q

long, limber fibers vibrate best at

A

low frequency

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13
Q

Fluid wave travels along

A

basilar membrane

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14
Q

fluid wave is strongest at

A

point of natural resonant frequency

at this point, membrane can vibrate back and forth with ease

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15
Q

fluid waves travel ____ initially then get _____

A

fast initally, then get progressively slower as it goes into chochlea

this allows high frequecy sounds to spread out and separate from one another

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16
Q

Pattern of sound wave

A

A - stapes is all the way in
B - Neutral
C - stapes all the way out

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17
Q

______ frequency waves are closest to stapes

A

higher

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18
Q

organ of corti role

A

generates nerve impulses in response to vibration of basilar membrane

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19
Q

Excitation of organ of Corti

A
  1. Stereocillia project upward from hair cells, which are embedded in gel coating of tectorial membrae
  2. bending of hairs in one direction depolarizes hair cells, bending in another direction hyperpolarizes them
  3. inward and outward movement of basialr fiber causes hairs to shear back and forth in tectorial membrane
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20
Q

____% of info comes from inner hair cells of organ of Corti

A

90-95%

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21
Q

what opens or closes mechanically gated ion channels in hair cells?

A

bending of sterocilia

22
Q

pivoting of steriocillia

A

opens or closes mechanically gated ion channels

23
Q

What is the electircle potential of hair cells at tips of sterocilia

A

+80
(creates extra sensitivity)

24
Q

place principle

A

determining sound frequencies by poition along basilar membrane

25
How does loudness occur
as sound becomes louder, amplitude of vibration in basilar membrane and hair cells increases -->more hair cells become stimulated (spatial summation)
26
decibel unit
10-fold increase in sound energy = 1 decibel logarithm of actual intensities
27
frequency of sound (age comparison)
young: 20-20,000 cycles per second older: 50-8,000 cycles per second young has broader range
28
Nerve fibers from spiral ganglion of Corti enter
dorsal and ventral cochlear nuclei in upper part of medulla-->2nd order neurons to opposite side of brain stem-->terminate in superior olivary nucleus
29
From superior olivary nucleus, auditory pathway
passes upward through lateral lemniscus where some fibers terminate and other -->colliculus where they synase
30
colliculus synapses to
medial geniculate nucleus -->synapse to auditory cortex
31
auditory synapse location
superior gyrus of temporal lobe
32
fibers pass through reticular activating system of brain stem, which:
activates nervous system in response to loud sounds
33
signals form both ears transmitted through the pathway of
both sides of the brain
34
Primary auditory cortex directly excited by
projections from medial geniculate body
35
Secondary association areas are excited secondarily by
impulses from primary auditory cortex
36
Sounds frequency perception
high frequency sounds excite nuerons at one side of tonotopic map, low frequency excite on other side
37
What "sharpens" frequency
lateral inhibition
37
Auditory cortex is important for
discrimination of tonal and sequential sound patterns
38
destruction of both primary auditory cortices would result in
reduced hearing
39
damage to only one primary auditory cortices results in
slightly reduced hearing and affects ability to localize sound
40
Lesions affecting auditory association area:
interfere with ability to interpret meaning of sound
41
How is direction of sound determined
time lag between entry of sound in one ear and entry into opposite ear = difference between intensities of the sounds in two ears
42
What determines if sound is front or behind, above of below?
Pinnae - changes quality of sound based on direction
43
Lateral superior olivary nucleus role
detecting direction from which sound is coming
44
medial superior olivary nucleus role
detects time lag between acoustic signals entering two ears
45
sounds from different areas around the head stimulate
different olivary neurons
46
Deafness can be caused by impairment of(3)
1. Cochlea 2. auditory nerve 3. CNS circuits from ear
47
Main cause of deafness
impairment of physical structures of the ear that conduct sound to cochlea
48
Permanent deafness MOA:
damage to cochlea or auditory nerve
49
Method for measuring hearing
audiometer - emits tone with ranging frequencies