lecture 11 - adrian rees

Question 1

sound travels by

Answer 1

rearefraction and compression of molecules

Question 2

frequency of sound wave is described as…

Answer 2

pitch

Question 3

amplitude is described as

Answer 3

loudness

Question 4

the outer ear

Answer 4

the pinna
auditory canal

Question 5

middle ear

Answer 5

ossicles (malleus, incus and stapes)

Question 6

inner ear

Answer 6

cochlea

Question 7

role of the pinna

Answer 7

helps to funnel sound into the ear canal
is also helps us localise sounds in the vertical plane

Question 8

auditory canal conducts sound down to the

Answer 8

tympanic membrane

Question 9

the auditory canal also causes…

Answer 9

acoustic gain due to resonance

Question 10

the sound reaching the tympanic membrane causes the tympanic membrane to vibrate then it is transmitted through the

Answer 10

ossicles

Question 11

what are the three ossicles

Answer 11

malleus, incus and stapes

Question 12

the footplate of the stapes connects to..

Answer 12

a window in the wall of the cochlea and allows the vibrations to enter the cochlea

Question 13

the middle ear pressure needs t be the same as the…

Answer 13

atmospheric pressure on the other side of the tympanic membrane

Question 14

if the atmospheric pressure changes how does the middle ear equilibrate

Answer 14

via the eustachian tube (connects to the nasopharynx, when you swallow the eustachian tube opens and allows the air pressure to equilibrate)

Question 15

the cochlea is ______ filled

Answer 15

fluid

Question 16

the middle ear acts as an….

Answer 16

impedance transformer (improves transfer from 3% to 60%)

Question 17

is the pressure greater at the tympanic membrane or the stapes

Answer 17

the stapes
this is because the area is smaller at the stapes and the force is the same (P = force/area)

Question 18

the malleus is longer than the incus (they act as a lever) so we get a larger movement in the malleus and a smaller movement in the incus but with

Answer 18

greater force

Question 19

lever ratio is 1.3 x and area ratio is 18 x so the total increase in pressure is 1.3 multiplied by 18 giving a

Answer 19

x 25 increase in pressure between the tympanic membrane and the stapes

Question 20

each nerve fibre is selective for a limited range of…

Answer 20

frequency

Question 21

what is the top compartment of the cochlea called

Answer 21

the scala vestibuli

Question 22

what is the bottom compartment of the cochlea called

Answer 22

the scala tympani

Question 23

what is in between the two compartments

Answer 23

scala media

Question 24

coming away from the cochlea at all levels are cochlea nerve fibres and the ganglion (where the cell bodies are found) is a…

Answer 24

spiral ganglion which spirals around the cochlea

Question 25

what is the membrane between the scala vestibuli and the scala media

Answer 25

reissner’s membrane

Question 26

what is the membrane between the scala media and the scala tympani

Answer 26

basilar membrane

Question 27

what structure sits on the basilar membrane

Answer 27

the organ of corti

Question 28

what membrane over lies the organ of corti

Answer 28

the tectorial membrane

Question 29

what fluid fills scala vestibuli and scala tympani

Answer 29

perilymph (high Na+)

Question 30

what fluid fills scala media

Answer 30

endolymph (high K+)

Question 31

there is a high conc of K+ in the scala media due to the epithelium called the…

Answer 31

stria vascularis which pumps potassium ions into the space

Question 32

the stereocilia of the outer hair cells embed into the

Answer 32

tectorial membrane

Question 33

the region in between the OHCs and IHCs is called the

Answer 33

tunnel of corti

Question 34

the stapes footplate goes backwards and forwards making contact with the oval window (a window onto scala vestibuli) at the frequency of the sound and that increases the pressure in the scala vestibuli when it pushes in out decreases the pressure pulls out. The round window (in the wall of the cochlea) bulges out when the stapes pushes in and pulls in when the stapes pulls out to accommodate the pressure changes. the pressure applied pushes the basilar membrane down, a wave travels along the basilar membrane to the apex. the cochlea is stiffer and the base and floppier at the apex. the stiffer part will vibrate first and the apex later. the displacement of the basilar membrane depends on the frequency of the sound. A high frequency sound causes most displacement at the…

Answer 34

base
and a low frequency sound causes most displacement at the apex