auditory processing

Question 1

Describe the structure of the inner ear

Answer 1

bony structure of cochlea and semicircular canals of vestibular system

Question 2

what is the cochlear

Answer 2

its a bony tube containing fluid in chambers separated by a thin membrane called the basilar membrane

Question 3

what happens when sound pressure waves enter the ear?

Answer 3

the ear sets up vibrations of the tympanic membrane (ear drum)
these virbations are then transmitted to the sensory receptors in the cochlea

Question 4

what happens when ‘sound’ enters the ear

Answer 4

the stapes vibrates and applies pressure to the fluid in teh upper chamber (scala vestibuli)
the fluid moves to the apex of the cochlea (helicotrema)
the fluid pressure is relieved by movement of additional membrane at the round window, which bulges out

Question 5

what leads to the vibration of the basilar membrane

Answer 5

compression and rarefaction of air in the outer ear

Question 6

as fluid moves around the helicotrema….

Answer 6

it exerts force onto the basilar membrane

Question 7

what is the structure of the basilar membrane like at the apex

Answer 7

5 times broader, thicker and floppier

Question 8

descripe the tonotopic organisation of the basilar membrane

Answer 8

high grequencies vibrate at round window end, low frequencies at apex

Question 9

what is the organ of corti comprised of

Answer 9

two rows of hair cells (inner and outer)

Question 10

what is the function of inner hair cells

Answer 10

main receptors responsible for perception of sound

Question 11

describe the structure of where hair cells are embedded

Answer 11

tips are embedded into gelatinous membrane (tectorial) that protrudes into a special fluid chamber called the scala media which has very high K+

Question 12

what happens to tips of hair cells when basilar membrane vibrates

Answer 12

shearing motion, deflected back and forth as tips adhere to tectorial membrane

Question 13

what about the hair cells can enhance the tonotopic map

Answer 13

fact that they are also longer and floppier at the distant end of the cochlea

Question 14

what ahppens to voltage when hair cells are pushed

Answer 14

the voltage change across the cell membrane is proportional to teh force encoding amplitutide and phase in their graded receptor potential

Question 15

what are tip links and what do they do

Answer 15

fine structures that connect the tips of stereocilia together
gate cation cahnnels
when pushed open, = K+ influx

Question 16

will the stimulus strength required to produce a 1mV response in hair cells be the same across the length of the basilar membrane

Answer 16

no because of tuning/sensitivity to different frequencies

Question 17

what is the relationship between the magnitude of sound and the perceived loudness

Answer 17

logarithmic = 10x the sound pressure for each increment in perception

Question 18

what explains our ability to perceive large dynamic range of volume

Answer 18

additional amplifiers = outer hair cells which generate sound in the ear to sharpen frequency tuning of inner ahair cells

Question 19

what is the speed of mechanical gating of ion channels

Answer 19

fast duh

Question 20

what do recordings from hair cells show

Answer 20

that they respond to sounds with graded responses which means the refractory period of spikes would be very limiting

Question 21

where is the ntsm released onto

Answer 21

the spiral ganglion neurons and then transmitted with action potentials

Question 22

why could a rate code not be used by receptors

Answer 22

it would lose resolution of timing (phase)

Question 23

hair cells fire ….. but auditory interneurons ap fire ….. at high frequencies

Answer 23

fast

slower

Question 24

is ap firing better or worse at lower amplitudes when its quieter

Answer 24

worse lol

Question 25

what lines up with the timing of spike generation

Answer 25

precisely in phase with depolarisation of hair cells

Question 26

why do we need multiple afferent interneurons per hair cell

Answer 26

because they miss info individually bc of the refractory period. so graded signal is converted to spike code for transmission to higher centres for processing

Question 27

how do we improve dynamic range

Answer 27

having different neurons with different thresholds for spike generation

Question 28

where do the spiral ganglion neuron cells project to

Answer 28

the cochlear nuclei in the brain stem in medulla

Question 29

describe the projection to the auditory cortex

Answer 29

its ascending pathway via relay nuclei in the mid brain = inferior colliculus (IC) and medial geniculate nucleus (MGN)

Question 30

what type of neurons does the IC contain

Answer 30

ones that respond only to specific sound locations

Question 31

what is cortex projection involved with

Answer 31

complex pattern recognition (speech)

Question 32

what can brain stem nuclei do

Answer 32

they are projected onto by spiral ganglion neurons. they compare sounds coming from two ears to determine the location of sounds in space (because of delay in sound reaching the more distant ea)