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physiology 3 > auditory and vestibular physiology > Flashcards

auditory and vestibular physiology Flashcards

1
Q

loudness

A

sound energy intensity (amplitude of vibration)

prolongued exposure to sounds > 90dB can cause damage

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2
Q

loudness expresssed in

A

dB

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3
Q

pitch

A

high or low sound
vibration frequency - Hz (cycles/sec)
human hearing range is 20 - 20000 Hz

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4
Q

human hearing range

A

20 - 20 000 Hz
infrasonic < 20
ultrasonic > 20 000
speech is 1500 - 5000, where hearing is most sensitive

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5
Q

parts of the ear

A 
outer (external) ear 
middle ear (ossicles) for hearing 
inner ear (labyrinth) for hearing and equilibrium
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6
Q

receptors are located

A

receptors for hearing and equilibrium are located in the inner ear

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7
Q

3 ossicles

A

malleus - hammer
incus - anvil
stapes - stirrup

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8
Q

pressure is equalised by the

A

pharyngotympanic tube (eustachian) which connects to naso-pharynx (compressed to be closed unless opened by pressure)

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9
Q

what do the ossicles do

A

articulate to form a lever system that amplifies and transmits the vibratory motion of the tympanic membrane to fluids of inner ear cochlea via oval window

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10
Q

2 muscles used for the tympanic reflex

A

stapedius and tensor tympani

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11
Q

tympanic reflex

A

loud sounds causes stapedius and tensor tympani to contract which limits vibration, to dampen the noise

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12
Q

stapedius attached to

A

stapes

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13
Q

tensor tympani attached to

A

malleus

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14
Q

membranous labyrnth

A

fleshy tubes lining bony labyrinth
fillied with endolymph ( similar to intracellular fluid)
floating in perilymph - similar to CSF

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15
Q

mambranous larynth is filled wth

A

endolymph - high concentration of potassium

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16
Q

mambranous labyrinth is floating in

A

perilymph

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17
Q

cochlea

A

contains hearing receptors

organ of corti with hair cells

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18
Q

3 chambers of the cochlea

A
  • scala media (cochlear duct) middle chamber
  • scala vestibuli - superior chamber
  • scala tympani - inferior chamber
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19
Q

cochlea chambers are filled with

A

fluid

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20
Q

scala media

A

cochlear duct
middle chamber
contains hearing receptors
filled with endolymph

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21
Q

scala media is separated from scala vestibuli by

A

thin vestibular membrane

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22
Q

scala media seperated from scala tympani by

A

thicker basilar membrane

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23
Q

scala vestibuli

A

superior chamber
filled with perilymph
begins at oval window

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24
Q

scala tympani

A

inferior chamber
filled with perilymph
begins at round window

25
Q

hair cells

A

hair cells on basilar membrane; stereocilia embedded in gelatinous tectorial membrane

26
Q

inner hair cells

A

1 row
3500
gives hearing

27
Q

outer hair cells

A 
3 rows 
20 000 
dont do hearing 
modulatory 
adjusts response of cochlea to different frequencies
28
Q

hair cell receptors contain

A

mechanosensitive ion channels

29
Q

mechanosensitve ion channels in hair cells

A

bathed in endolymph (high K fluid)

  • creating electrochemical gradient
  • outside of cell is +80mV and inside of cell in near -40mV
  • mechanically gated K channels
30
Q

stereocilia

A

stick out of hair cell

attached to potassium channel

31
Q

when stereocilia are bent

A

when bent, open mechanossensitive potassium channel causing potassium to enter cell
cell depolarises

32
Q

hearing process

A
  • vibration at oval window causes displacement of basilar membrane
  • sensory inner hair cells mechanically stimulated by waves (squished against tectoral membrane)
  • K flux generates receptor potentials, neurotransmitter release
  • action potentials fire down cochlear nerve
33
Q

amplitude

A

loudness
intensity of cochlear vibrations
- louder sounds make the basilar membrane vibrate more vigorously
- triggers higher frequency of action potentials
- brain interprets this as louder sound

34
Q

frequency

A

pitch
basilar membrane location
low frequencies penetrate further - high frequency sounds penetrate less far
sound making it further around the cochlear is determined to be lower frequency

35
Q

why doo we have more outer than inner hair cells

A

outer hair cells are more modulation
stereocilia dont have potassium channels
modify responsiveness
when sound is loud - prestin (motor protein) strenghthens stereocilia

36
Q

prestin

A

motor protein
strenghtens stereocilia when there is loud sound
dampens vibrations between tectoral membrane and inner hair cells

37
Q

electromechano transduction

A

excitation atcivates motor protein (prestin)
frequency specific effect
not the same all the way through the cochlear

38
Q

hearing loss may be

A
  • sensorineural

- conductive

39
Q

sensorineural hearing loss

A

permanent
age, noise, or frequnecy related
sensory = cochlea hair cells
neural = (retrocochlear) cochlea nerve path

40
Q

conductive hearing loss

A

loss of sound conduction via middle/outer ear

blockage, damage, infection

41
Q

equilibrium

A

coordination, balance and orientation in three dmensonal space
only special sense for whichh most of the information goes to lower brain centres

42
Q

static equilibrium

A

the perception of the orientation of the head when the body is stationary

43
Q

dynamic equilibrium

A

perception of motion or acceleration

  • linear acceleration - change in velocity in a straight lne
  • rotational acceleration - change in the rate of rotation
44
Q

semicircular ducts

A

3 ducts

detect only rotational acceleration

45
Q

vestibular chambers

A

2 chambers
anterior saccule and posterior utricle
responsble for static equilibrium anf linear acceleration

46
Q

2 chambers are callled

A

saccule and urticle

47
Q

chambers conatin

A

saccule and urticle each contain a macula

48
Q

role of the macula

A

senses static equilibrium and linear acceleration of the head
not rotational movements
hair is imbedded in otolithic membrane (statoconia)

49
Q

statoconia

A

motolithic membrane - ear rock

2-3x heavier than surrounding medium - gravity activated

50
Q

how does the macula work

A

gravity moves the statoconia with moves hair cells which trigger vestibular nevre which branches to vestibulocochlear nerve

51
Q

how do semicircular canals work

A

3 each lying in one of the 3 planes of space
sense rotational acceleration of the head
duct with ampulla housing a small crest - crista ampullaris
hairs project into jellylike cupula - fluid endolymph remains stationary-ish as head rotates (inertia) bands hairs
synapse wth fibres of vestibular nerve

52
Q

cupula

A

jellylike structure encompassing hair cells in the semicircular canals

53
Q

hair cells in the semicircular canal comes out of

A

crista ampullaris

54
Q

crista ampullaris is located in

A

ampulla of the semicircular canal

55
Q

hair cells in the semicircular canal synapse with

A

vestibular nerve

56
Q

5 areas vestibular information is projected to

A

cerebellum - integrates vestibular information into its control of head and eye movements, muscle tone, and posture
nuclei of occumlomotor, trochlear, and abducens nerves (CN 3, 4, 6) to produce vestibulocochlear reflex: keeps vision fixed on distant object while walking
reticular formation - thought to adjust blood circulation and breathing to postural changes
spinal cord - descend through vestibulospinal tracts and innervate antigravity muscles
thalamus - thalamus relay to cerebral cortex for awareness of position and motor control of head and body

57
Q

2 types of vertigo

A

peripheral and central

58
Q

peripheral vertigo

A

vestibular
benign paroxysmal positional vertigo (BPPV)
Ca2+ deposits in semicicrcular canals
32% of all peripheral vertigo

59
Q

central vertigo

A

CNS (pathways, brainstem, nuclei, cerebellum)

physiology 3 (7 decks)

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