Hearing

Question 1

hair cells

Answer 1

sensing cells in the ear

Question 2

hair cells contract

Answer 2

rapidly in synchrony with sound

-responding to pitch, tone and loudless

Question 3

Anatomy of the ear: what separates the outside of the ear (air) with the inner portion of the ear (fluid)

Answer 3

the ear drum

Question 4

sound waves travel

Answer 4

diff through air and fluid

Question 5

what allows the transmission of sound waves from the air to the fluid in the inner part of the ear

Answer 5

the OVAL window

Question 6

where is the oval window found

Answer 6

the ossicles

Question 7

three bones of the ossicles

Answer 7

malleus, incus and stapes- conduct vibrations to the oval window

Question 8

the organ of corti

Answer 8

is the hearing sensing organ

Question 9

organ of corti is made up of

Answer 9

hair cells, which are connected to the tectorial membrane and the basilar membrane

Question 10

tectorial membrane is closest to the

Answer 10

scala vestibular

Question 11

basilar membrane is closest to the

Answer 11

scala tympani

Question 12

the scala vestibular, scala media and scala tympani are all filled

Answer 12

with special, differing fluids –> mechanical sensing

Question 13

how vibration is conducted around the cochlea

Answer 13

vibration transferred to oval window

- generates fluid wave down the scala vestibule, then through to the scala tympani to the round window

Question 14

as the sound passes around the cochlea

Answer 14

the vibrations are also conducted to the organ of corti, via a displacement of the membrane

Question 15

three differing fluids of the ear are located in

Answer 15

the scala vestibular/ tympani (ECF), the scala media (endolymph) and the hair cell (ICF)

Question 16

fluid in the scala vestibular/ tympani

Answer 16

extracellular fluid

Question 17

fluid in the scala media

Answer 17

endolymph

• similar to intracellular fluid
• VERY HIGH CONC OF POTASSIUM (150 mmol/L
• potential of +80mV
• low sodium conc

Question 18

how the different fluid compositions work

Answer 18

electrochemical potential between these fluids

Question 19

where is there the highest conc of potassium

Answer 19

the endolymph within the scala media

Question 20

there are fewer

Answer 20

inner hair cells and they ar ea single row

Question 21

outer hair cells (further into the cochlea)

Answer 21

parallel rows of cilia of hair cells embedded into tectorial membrane

Question 22

base of hair cells is in contact with the

Answer 22

basilar membrane- which is more flexible- transmits wave

Question 23

cilia are bathed in

Answer 23

a high conc of potassium

Question 24

outer hair cells

Answer 24

amplify the vibration

Question 25

when strain is put on the basilar membrane

Answer 25

strain is put on the cilia, therefore they will bend in response

Question 26

this strain

Answer 26

will open and close mechanically gates K+ channels | - causing depolarisation and repolarising

Question 27

potassium is

Answer 27

recycled through the structure

Question 28

cochlear nerve fibres than transit AP

Answer 28

to the CN VIII part of the CNS- vestibulocochlear nerve

Question 29

overal process of hearing

Answer 29

1) sound wave 2) vibration of organ of court 3) bending oc cila on hair cells 4) change in K+ (mechanically gated) conductance of hair cell membrane 5) Oscillary receptor potential (cochlear microphonic) 6) intermediate glutamate release 7) excitatory to NMDA/ AMPA 8) intermittent AP in afferent cochlea nerves 9) cranial nerves 10) temporal pathway

Question 30

pitch is determined by

Answer 30

frequency of the signal

Question 31

higher frequencies

Answer 31

closer to the oval widnow

Question 32

lower frequencies

Answer 32

near helicotrema

Question 33

loudness

Answer 33

identified by the amplitude of deflection at a given part of the cochlea

Question 34

inner hair cells

Answer 34

Transduce the mechanical signal (vibration) into an electrical one via opening of mechanically gated K+ channels

Question 35

outer hair cells

Answer 35

At to amplify the vibration by adjusting their length to modify the basilar membrane (positive feedback)