Auditory system

Question 1

What features of sound does the auditory system need to encode?

Answer 1

Frequency
Intensity
Onset
Duration

Question 2

How many chambers does the cochlea have?

Answer 2

3

Question 3

What are these chambers?

Answer 3

Scala tympani
Scala media
Scala vestibuli

Question 4

What is the Organ of Corti?

Answer 4

It is at the bottom of the scala media and contains the sensory hair cells and receives innervation from the auditory nerve

Question 5

Where is perilymph found?

Answer 5

Scala vestibuli and tympani

Question 6

What is its relative K+ concentration and Ca conc? (perilymph)

Answer 6

Low K+ and normal Ca

Question 7

What contains endolymph?

Answer 7

Scala media

Question 8

What are its concentrations of K+ and Ca? (endolymph)

Answer 8

High K+ and Low Ca

Question 9

What produces endolymph?

Answer 9

Stria vascularis – pumps K+

Question 10

What is the membrane potential in the scala media and in the Vm for the hair cells in the organ of corti?

Answer 10

Scala media = +80mV

Hair cell Vm = -60mV

Question 11

What is the name for this difference in potential?

Answer 11

Endocochlea potential

Question 12

Which hair cell is the main sensory cell?

Answer 12

Inner hair cell

Question 13

What is the function of the outer hair cells?

Answer 13

Amplify signals

Question 14

What do the outer hair cells make contact with?

Answer 14

Tectorial membrane

Question 15

How many bundles of outer hair cells are there?

Answer 15

3

Question 16

Where are the low frequency inner hair cells?

Answer 16

At the top

Question 17

What does each inner hair cell code for?

Answer 17

Particular frequency

Question 18

What causes the hair cells to move?

Answer 18

Movement of the basilar membrane due to the travelling wave in the scala tympani
- Low frequency travels further along basilar membrane

Question 19

What does MET stand for? (MET channels)

Answer 19

Mechanoelectrical transducer channels

- Allow current in

Question 20

Where are they found?

MET channels

Answer 20

On the end of the stereocilia hair bundles

Question 21

What do tip links do?

Answer 21

Connect and pull on hair bundles

Question 22

What happens when there is an excitatory deflection?

Answer 22

Maximal tip link extension that fully depolarises the hair cell

Question 23

What happens when there is an inhibitory deflection?

Answer 23

No tip link extension and hair cell is hyperpolarised

Question 24

What is the role of the OHC?

Answer 24

Amplify sound

Question 25

What fibres contact the OHC?

Answer 25

Efferent fibres

Question 26

What allows the OHC to contract?

Answer 26

Prestin in the cell membrane

Question 27

What happens when there is depolarisation to the OHC?

Answer 27

Contraction

Question 28

What does contraction in OHC do?

Answer 28

Increase movement of basilar membrane and IHC stimulation

Question 29

What tunes the IHC?

Answer 29

OHC to ensure IHC responds to a narrow frequency band

Question 30

What do type 1 afferents contact?

Answer 30

IHCs

Question 31

In which way does the auditory system encode the property of sound which is measured on a logarithmic scale?

Answer 31

The rate of firing of action potentials

Question 32

What is the auditory pathway?

Answer 32

superior olivary complex → superior colliculus → medial geniculate nucleus

Question 33

Why are low frequency sounds generally localised by interaural timing differences?

Answer 33

high frequency sounds are more susceptible to attenuation by the head

Question 34

What do the OHC receive efferent input from?

Answer 34

Superior olivary complex