The Auditory System

Question 1

air particles

Answer 1

vibrate back and forth

Question 2

rarefied air vs compressed

Answer 2

packets of less dense air vs dense air

creates sound wave

Question 3

frequency

Answer 3

number of compressed or rarefied patches of air that pass ear each second , Hz
peak - rarefied
trough - compressed

Question 4

intensity

Answer 4

air pressure difference between peaks and troughs, dB

small difference = low intensity

Question 5

range of human hearing

Answer 5

20Hz - 20,000Hz
4,000Hz = best frequency
thresholds
high risk e.g. rock connects = 120dB
pain e.g. gun shot = 140dB

Question 6

anatomy of auditory system

Answer 6

outer ear - pinna and tympanic membrane
middle ear - tympanic membrane to oval window - air filled compartment
inner ear - oval window to cochlea and vestibular system

Question 7

pinna

Answer 7

bit you can see

localises sound in vertical plane

Question 8

tympanic membrane

Answer 8

ear drum

vibrates with sound waves - causes movement of ossicles

Question 9

oval window

Answer 9

moves back and forth with ossicles

Question 10

cochlea and vestibular system

Answer 10

cochlea - fluid filled, contains tranducers

Question 11

ossicles of middle ear

Answer 11

malleus - hammer, attached to tympanic membrane
incus - anvil, rigid connection with malleus
stapes - stirrup, flexbile connection with incus, attaches to oval window

Question 12

how does middle ear transfer sound?

Answer 12

middle ear takes large SA sound from tympanic membrane and converts to small SA on oval window - concentrates force of each sound eave

Question 13

why concentrate sound in middle ear?

Answer 13

we live in air filled environment, ear is fluid filled, it is more difficult fo waves to move through fluid so need to concentrate them so no energy is lost as it moves through

Question 14

if soundwave pushes inwards…..

Answer 14

bottom of maleeus moves down

point of incus pushes forward and pushes stapes into oval window = causes fluid movement along cochlea

Question 15

round window

Answer 15

in cochlea

allows fluid to push out, reduces resistance

Question 16

if sound pulls outwards…..

Answer 16

tympanic membrane moves out
malleus moves uo
incus pulls back
pulls stapes out with oval window

Question 17

anatomy of cochlea

Answer 17

oval window joins at bottom and causes movement of fluid up to apex
meets helicotrema where fluid moves into different compartemtn back on itself

Question 18

each spiral of cochlea has 3 compartments

Answer 18

scala vestibular
scala tymani
scala media

Question 19

scala vestibular

Answer 19

fluid intially pushed through from oval window

filled with perilymph - extra cellular fluid

Question 20

scala tympani

Answer 20

connects to round window

filled with perilymph

Question 21

scala media

Answer 21

filled with endolymph - high K, only found in inner ear, high potential

Question 22

path of fluid in cochlea

Answer 22

move up through vestibular - hit helicotrema - move down through tympani

Question 23

organ of corti

Answer 23

runs along spiral, from base to apex, contains transducers that sit on basilar membrane

Question 24

basilar membrane

Answer 24

runs along coil of cochlea
hair cells sit on top
tectorial membrane sits on top of hair cells

Question 25

hair cells

Answer 25

3 rows of outer hair cells
1 row of inner hair cells
all have stereo cilia - move back and forth with fluid movement
each haiir cell has 3 rows of cilia in staircase

Question 26

inner hair cell

Answer 26

primary tranducer
hair bundles surrounded by endolymph
cell body = perilymph

Question 27

anatomy of basilar membrane

Answer 27

different properties depending where it is
at basal end - high freq sound smake membrane move more
at apex - low feq make membrane move
creates tonotopic map
basal = stiff, thick, narrow
apex = wider and less stiff

Question 28

how does basilar membrane affect hair cells?

if stapes is pulled out….

Answer 28

fluid moves out

membrane pushes upwards, tectorial membrane moves and pushes stereocillia towards tallest one = depolarisation

Question 29

how does basilar membrane affect hair cells?

if stapes moves in….

Answer 29

membrane moves in

hair cells move towards smallest one = hyper polarised = no signal down auditory nerve

Question 30

hair bundles

Answer 30

connected by tip links - pull open channels for transducing
broken tip links—-> noise induced hearing loss
at top of shortest cilia = mechanoelectrical transducer channel
pushing towards tallest - opens channel - K moves in

Question 31

if cilia push towards tallest

Answer 31

stretched tip link
channels open and K floods in
depol of hair cells - moves to base of cell
opens voltage gated Ca channel and Ca floods into cell
causes exocytosis of glutamate vesicles
actiavtes afferent neuron

Question 32

if cilia push towards smallest

Answer 32

tip link shortens
shuts channel - no K
hyperpolarised
Ca channels dont open
no action potential

Question 33

outer hair cells

Answer 33

electromotive
act as cochlear amplifiers
'dancing hair cells'
make inner cell responses bigger - can hear at lower intensities 
amplify basilar membrane movement