auditory system

Question 1

functions of sound

Answer 1

communication
emotion
sound recognition
3D view of world
survival

Question 2

what features of sound are encoded

Answer 2

frequency Hz (pitch)
intensity dB (volume)
onset
duration

Question 3

pathway of sound

Answer 3

external auditory canal -> tympanic membrane -> tympanic cavity (ossicles) -> round window -> cochlea

Question 4

chambers of cochlear spiral

Answer 4

scala vestibuli
scala media
-> organ of corti
scala tympani

Question 5

organ of corti

Answer 5

contains hair cells
sensory transduction
in scala media

Question 6

organisation of mammalian cochlea

Answer 6

tonotopic organisation
spiral structure = extends freq range (as many hair cells in space)
- cells at base = high freq
- cells at apex = low freq

Question 7

place frequency code

Answer 7

position of active IHC along cochlea that encodes the sound freq

Question 8

how does sound of one frequency activate a specific IHC?

Answer 8

• cochlear tonotopicity is established by basilar membrane travelling wave
• Sound of one frequencycauses maximal movement of the basilar membrane (BM) at one location

Question 9

what is characteristic frequency

Answer 9

Sound of one frequencycauses maximal movement of the basilar membrane (BM) at one location

Question 10

low freq sound features

Answer 10

• high energy → travels further along BM
• causes maximal movement toward apex
• CF location closer to apex
• long wavelength

Question 11

high freq sound features

Answer 11

• low energy → travels less far along BM
• maximal movement toward base
• CF location closer to base
• short wavelength

Question 12

characteristic frequency is determined by

Answer 12

width and stiffness of basilar membrane

Question 13

what freq are base hair cells stimulated by

Answer 13

high freq

Question 14

what freq are apex hair cells stimulated by

Answer 14

low freq

Question 15

what are the primary sensory receptors of auditary system

Answer 15

inner hair cells

Question 16

how is sound tranduced to an electrical signal

Answer 16

travels through ear into cochlea and moves basilar membrane in a position dependent on freq (determines what sound)
perilymph in SV and ST move hair bundles on inner hair cells causing shorter stereocilia to move toward longer stereocilia and transducer channels to open. Influx of calcium -> afferent neurone

Question 17

voltage of resting IHC

Answer 17

-55mV

Question 18

voltage of excited IHC

Answer 18

-30mV

Question 19

voltage of inhibited IHC

Answer 19

-65mV

Question 20

sustained stimulation of inner hair cells

Answer 20

• hair cell moves back and forth at sound frequency
• cycle of membrane potential matching sound frequency
• sensory info relayed to brain via afferent neurone

Question 21

K movement through IHC during stimulation

Answer 21

enters down electrical gradient and leaves down chemical gradient due to separation of endo and perilymph

Question 22

role of outer hair cells

Answer 22

amplification of cochlea by moving basilar membrane more

Question 23

structural differences of outer hair cells

Answer 23

V shaped hair bundle
3 rows
containes prestin in cell membrane allowing stereocilia to lengthen and shorten in response to sound -> moves BM

Question 24

resting potential of outer cells

Answer 24

-40mV

Question 25

outer hair cells response to stimulation/inhibition

Answer 25

stim = depolarised = shorten in length (moves BM down)
inhib = hyperpolarised = lengthen