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PHGY 209 > CNS/sensory 5 - auditory > Flashcards

CNS/sensory 5 - auditory Flashcards

1
Q

describe amplitude and frequency of sound

A

changes of pressure around head
auditory system detects changes in pressure

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2
Q

what are hertz

A

number of cycles per second = frequency = pitch

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3
Q

what is amplitude

A

Loudness

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4
Q

describe normal audibility curve

A

dB = 20log (sound pressure/reference pressure
20 change in db = 10 times louder

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5
Q

descrive frequency range of humans

A

~10khz
to 20 khz
human voice = 1-4khz

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6
Q

what is damage threshold

A

less than pain threshold
not just loudness but duration
Around 80db

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7
Q

what is presbycusis

A

adavancing age = loss of hearing at high frequencies (>1000hz)

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8
Q

what is external auditory cannal

A

pinna reflects pressure wave into it

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9
Q

what is pinna

A

folds = reflect certain frequencies of sounds into external auditory canal

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10
Q

what is middle ear

A

has 3 smallest bones in body
malleus, incus, stapes
connects tympanic membrane to another membrane on other side of ear

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11
Q

what is inner ear

A

in skull

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12
Q

what is cochlea

A

shell

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13
Q

what is eustachian tube

A

middle ear attached to back of throat through this
can hear in airplane - open mouth and equalize pressure in middle ear, also when have cold = inflammation and cannot regulate pressure well

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14
Q

what is tympanic membrane

A

strike eardrum

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15
Q

what is semicircular canals

A

loops of vestibular system

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16
Q

what is oval window

A

flexible membrane that transmits sound in ear

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17
Q

what is round window

A

another membrane

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18
Q

what is sensory epithelia

A

where afferent are for cochlea = perception of sound waves occurs, transduction and vestibular organs

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19
Q

what is utricle and saccule

A

vestibular organs
encodes horizontal and vertical acceleration of head

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20
Q

name vestibular organs

A

5 of them = 3 semicircular canals, utricle, saccule

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21
Q

describe flow of sound energy - beginning

A

tympanum = pushed by pressure waves
amplification modulated by skeletal muscles
linked to oval window by 3 bones = malleus, incus, stapes

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22
Q

what happens to tympanum when pressure

A

pressure decrease= eardrum pulled out
pressure increase=eardrum pushed in

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23
Q

describe amplification modulated by skeletal muscles

A

mechanical coupling of tiny bones innervated by skeletal muscles
contract when loud noise since limited range in which they can move = contract before sound to reduce amount of movement
if do not expect sound = will not contract and do job
large eardrum but small oval window = so force amplified, behind window = fluid

24
Q

describe flow of sound energy - end

A

oval window = flexible membrane, pushed in or out, pressure waves go to flui
scala vestibuli = attached to oval window and pushes pressure waves down cochlea, fluid filled compartment
then comes back down
scala tympani
basilar membrane = vibrates up and down in response to pressure waves in compartments, mechanical properties of basilar membrane not uniform across cochlea
oval window pushes in = pushes out round window which moves back and forth
cochlear duct = scala media - in between 2 other scala

25
motion of basilar membrane is
Frequency dependent locations of vibrations are a function of frequency of sound
26
describe where frequencies fall on basilar membrane
low frequencies = towards tip of cochlea as frequencies increase = vibrations move closer to oval and round window complex sounds = vibrations in multiple locations
27
what does basilar membrane encode
frequency of sound in location dependent manner
28
where is basilar membrane motion converted into neuronal activity
organ of corti on top of basilar membrane = where afferent located
29
what does deflection of basilar membrane produce
shearing of hair cell stereocilia
30
describe organ of corti
4 rows of specialized hair cells down cochlea hair on apical surfaces
31
describe inner hair cells
1 row where afferents and transduction from afferent synapse onto hair cells = release neurotransmitter and sends info to brain
32
describe what happens as basilar membrane moves to the stereocilia
stereocilia moves (activated to tectorial membrane) bend or pulled in ways = move back and forth
33
describe outer hair cells
some afferents come from 3 outer rows of hair cells but really receive afferents
34
describe outer hair cell electromotility
shorten when depolarized lengthened when hyperpolarized hair cell electromobility augments basilar membrane motion alter how basilar membrane vibrates = allows cns to focus on certain properties by activating outer hair cells
35
describe clinical implications of outer hair cell electromotility
otoacoustic emissions = reflex, are used to evaluate hearing in newborns outer hair cells make noise, do not hear them tho, makes click and can hear with microphone way to test functioning = play click and wait for it to come back, if dont hear click = outer hair cells not doing what they should hearing is important for language development
36
what do hair cells contain
mechanoreceptors bend stereocilia
37
describe bending of stereocilia
Distance between ends of stereocilia are getting small as they are pushed or bent = clue as to where ion channels are
38
what connects stereocilia
tip links = tiny molecular threads attaching them
39
describe tip links
coated tip links between stereocilia ~15000 hair cells/inner hair cells in reach row = where transduction occurs do not have many hair cells in cochlea ~10-20 stereocilia and one tip link per cell = ~100000 or 200000 tip links per cochlea When break = problem
40
where are ion channels on cilia
on each side of tip link as they move = tip link string pulls open channels when stereocilia move further apart when move closer togetehr = tip links relax = less tension to ion channels close
41
what do tip links do
gate ion channels in stereocilia each side ot tip link between taller and shorter stereocilia pulls ion channel and lets potassium through = transduction
42
what does mechano transduction at tip link activate
afferent neurons
43
describe mechanotransduction at tip link
move in direction of tallest stereocilia = open move in other direction = close
44
describe moving in direction of tallest stereocilia
k+ comes in and depolarizes cell and causes influx of calcium and neurotransmitter released on afferent and send ap to brain
45
why does potassium cause depolarization
fluid in cochlear duct is different from other fluids = it has high potassium, usually low potassium in ecf and high in cells but opposite in cochlear duct
46
what is tinnitus
ringing in ears permanent does not stop
47
name 2 types of tinnitus
transient chronic
48
describe transient tinnitus
less and 24 hrs usually due to loud noise excessive mechanical stress of stereocilia tip links are though to break but eventually grow back = ringing stops
49
describe chronic tinnitus
many causes but mostly loud noise origin can be either inner ear, nerve or central pathways Impacts quality of life - does not stop mechanical damage or if damage to central auditory pathways
50
compare visual and auditory transduction - visual
photons = high energy but hard to catch, ~100x10^6 photoreceptors trillions of opsin molecules slow = g protein cascade amplification closes many ion channels
51
compare visual and auditory transduction - auditory
sound waves = low energy but all around ~15000 hair cells, easy to catch but low energy Several hundred thousand tip links fast = direct channel activation no amplification of transduction (yes mechanical but not of transduction)
52
describe cochlear implant
hair cell loss due to aging, loud sounds, ototoxic drugs reestablish hearing in deaf
53
describe process of cochlear implant
implanted through round window electrode place in scala tympani Electrodes are spaced along the cochlear spiral to stimulate groups of afferent fibers that respond to different frequencies ~12 electrodes sounds a bit diff but does work
54
what is deafness usually due to
transduction process does not work but afferents still there so cochlear implants take sound through microphone and transmit through electrodes --> stimulates afferents and fire aps decomposes frequency of sounds and stimulates right electrode in right location = figure out what frequencies are in sound= what basilar membrane does
55
describe central auditory pathways
8th cranial nerve - vestibular and auditory enters brainstem at level of medulla bilaterally represented across midline = ipsilateral and contralateral at same time Thalamus primary auditory cortex = recieves input from both ears
56
why is it important that receive info from both ears
use differences between sounds that being sent from each ear to do sound localization
57
name 3 steps to locating source
1 - time it takes sound to enter and activate cochlea on both sides (sound on left hits right cochlea later, microseconds but neurons are sensitive to it) 2 - head blocks pressure waves so amplitude depends on how its coming towards you 3 - pinna (ear) reflects sound coming in diff directions and also helps determine ability to locate sound neurons use slight differences to help determine where sound is coming from

PHGY 209 (19 decks)

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