BMS11004 WEEK 8 - THURSDAY

Question 1

outline what sound actually is

Answer 1

particles move backward/forward in small area ‘vibrating’
sound waves travels along the whole length, as move create rareified and compressed air

Question 2

outline rareified air

Answer 2

low density of particles

Question 3

outline compressed air

Answer 3

high density of particles

Question 4

outline sound frequency

Answer 4

number of compressed or rareified patches of air that pass by our ears each second, expressed in Hz

Question 5

describe what frequency like at less or more particles

Answer 5

less particles = low frequency sound
more particles = high frequency sound

Question 6

define intensity/amplitude of sound

Answer 6

air pressure difference between peaks and troughs, in dB

Question 7

what does greater intensity/amplitude mean

Answer 7

bigger air pressure difference

Question 8

what is human hearing range

Answer 8

20-20,000Hz

Question 9

what is baseline of profound hearing loss

Answer 9

100Db

Question 10

why does 0Db not mean there’s no sound

Answer 10

logarithmic scale

Question 11

what is role of the outer ear

Answer 11

funnel sound wave
more sensitive to sound from infront than from behind
convolutions of pinna (outer ear squiggle) for sound localisations

Question 12

briefly outline structure of middle ear

Answer 12

tympanic membrame, 3 ossicles, oval window, cochlea

Question 13

what is tympanic membrane (middle ear)

Answer 13

ear drum, move back/forth like speaker
when moves, causes movement in ossicle

Question 14

name 3 ossicles of middle ear

Answer 14

malleus, incus, stapes

Question 15

what is oval window (middle ear)

Answer 15

covers base of cochlea, similar to tympanic membrane but smaller

Question 16

why would oval (middle ear) hardly move if moved directly by sound

Answer 16

air-fluid interface, fluid has greater inertia
cochlea is fluid filled compartment

Question 17

explain how middle ear transfers sound

Answer 17

rareified patches of air pulls tympanic membrane outwards so pulls oval window out of cochlea (pull fluid in cochlea in opposite direction)
transfers movement of tympanic membrane from oval window to create fluid movement in cochlea
middle window concentrate force of sound waves against larger tympanic membrane onto smaller oval window

Question 18

how does ossicles of middle ear amplify sound

Answer 18

exerts 20x more pressure onto oval window than to tympanic membrane
overcome greater impedance of cochlear fluid

Question 19

what 3 fluid-filled compartments surround the cochlea spiral

Answer 19

scala vestibuli, scala media, scala tympani

Question 20

outline scala vestibuli (cochlea)

Answer 20

connected to top of oval window, gets pushed at bottom if oval window gets moved in, pushes fluid (perilymph) down into scala tympani

Question 21

outline scala tympani (cochlea)

Answer 21

filled with perilymph, connect at large end to round window

Question 22

outline scala media (cochlea)

Answer 22

filled with different solution, endolymph, with very high extracellular K+ surrounds stereocilia (hair bundles)

Question 23

what is organ of corti

Answer 23

mid of cochlea
top of organ of corti has tectorial membrane (underneath there are outer hair cells)

Question 24

what is role of hair cells in organ of corti (cochlea)

Answer 24

inner line = primary transducers of auditory system
outer line = less important, help amplify cochlea response, help inner hair cell listen to low db

Question 25

explain hair bundles and tip link

Answer 25

hair cell has hair bundle at apex, made of stereocilia which is connected by tip links (broken by loud music)
when tip links pulls, open mechanoelectrical transducer channels (non selective cation channel) and allow flow in of cation, depolarise hair cell

Question 26

outline basilar membrane

Answer 26

runs along cochlea, moved when cochleal fluid moves
thick at base and thinner at apical end

Question 27

what does different frequency sounds cause in basilar membrane

Answer 27

maximal displacement
high frequency cause more movements
low frequency makes apical end move more
tonotopic map (cell responsive to different frequencies found in different place on each levels)

Question 28

explain how movement of the basilar membrane not linear

Answer 28

amplitude of movement not proportional to the sound pressure

Question 29

how does basilar membrane displacement (bowing upward) affect hair cells

Answer 29

stapes move outward, BM move upwards
moves hair cell up, stretch tip link, opens channel- depolarisation

Question 30

how does basilar membrane displacement (bowing downward) affect hair cells

Answer 30

stapes move inward, BM move downwards
hair cells move down, relaxes tip link, shut channel- hyperpolarisation

Question 31

why is endolmyph at a higher voltage

Answer 31

high K+

Question 32

why is perilymph at a lower voltage

Answer 32

low K+

Question 33

describe why outer hair cells are electromobile, and what this allows

Answer 33

when cell voltage change, MP change, they move and change size
so are able to amplify movement of basilar membrane, acting as cochlear amplifier