Hearing

Question 1

describe sound

Answer 1

has wave/particle properties

consists of compression (peak) and rarefaction (trough)

Question 2

pitch and loudness are determined by

Answer 2

frequency and amplitude (intensity)

Question 3

parts making outer ear?

Answer 3

pinna, auditory canal

Question 4

parts making the middle ear?

Answer 4

tympanic membrane; ossicles (hammer (malleus)/anvil (incus) /stirup (staples))

Question 5

parts making the inner ear?

Answer 5

cochlea

Question 6

how does the inner ear increase pressure exerted onto cochlea?

Answer 6

p=f/SA
SA of oval window 20x smaller than that of tympanic membrane; hence 20x pressure exerted
ossicles increase force

Question 7

how is damage against large vibrations reduced

Answer 7

via the attenuation response

-tensor tympani and stapedius muscles contract, reduicing vibrations to voal window

Question 8

describe the cochlea structure

Answer 8

one continuous hole, filled with perilymph
top = scala vestibuli; bottom = scala tympani
middle hole called scala media, filled with endolymph (high [K+])
inside the scala media is the organ of corti: has hair cells, tectorial membrane, basilar membrane
apex (top) and base

Question 9

what happens inside cochlea when compression occurs

Answer 9

staples push into it

basilar membrane goes down

Question 10

what happens inside cochlea when rarefaction occurs

Answer 10

staples pulled out of cocluea

basilar membrane goes up

Question 11

considering that sound is a combination of compression and rarefaction, what happens to basilar membrane

Answer 11

goes up and down

Question 12

how does frequency locate to vibration location on basilar membrane

Answer 12

base is stiffer and thinner, hence more sensitive to higher frequencies than the apex

Question 13

what part of inner hair cells enables opening of ion channels

Answer 13

stereocilia; ion channels connected by tiplink proteins

when stereocilia are deflected, tiplink proteins are stretched, enabling ion flow into it

Question 14

describe inner hair cell innervation

Answer 14

by 9-10 spiral ganglion cells. they spike when enough glutamate from the IHC is received

Question 15

describe how AP is formed in spiral ganlgion cell, from the IHC

Answer 15

basilar membrane vibrates.
deflects stereocilia
tiplink proteins cause ion channels to open
K+ from endolymph goes in, causing depolarisation.
Ca2+ causes glutamate release
glutamate binds to SGC’s, casing AP`

Question 16

describe interaural time delay

Answer 16

• Sounds coming from the front will reach the ears at the same time
• Sounds coming from the right will reach the right ear earlier (0.6s)

Question 17

describe interaural level difference

Answer 17

• Sounds coming from the front will reach the ears with the same intensity
• Sounds coming from the right will reach the right more loudly, and the left less loudly (as the head blocks the sound)

Question 18

describe phase locking

Answer 18

• Doesn’t have to occur for every AP, as long as its at the same point of the phase
• At high frequencies (>5kHz) phase locking won’t occur.