Hearing

Question 1

What does each wave component determine in sound
wavelength
amplitude
waveform

Answer 1

wavelength = frequency = pitch 
amplitude = loudness
waveform = how smooth the sound

Question 2

What is the function of the pinna

Answer 2

localise and collect sound

Question 3

what is the function of ossicles?

Answer 3

impedance matching

without it, sound wave from air will just reflect off the fluid medium

Question 4

how do we overcome the impedance?

Answer 4

by providing a 200x the pressure.

Question 5

How is the 200x pressure generated?

Answer 5

by the relative size of tympanic membrane and the lever action of the ossicles

Question 6

What are the three chambers of the cochlea?

Answer 6

Scala vestibuli
Scala media
Scala tympani

Question 7

What’s the difference between scala vestibuli and scala tympani?

Answer 7

Nothing really, they are continuous at the apex, but otherwise separated by the cochlear duct

They both carry perilymph

Question 8

The apex is _______ and ______, which is able to detect ______ frequency sound.

The base is _______ and ______, which is able to detect ______ frequency sound

Answer 8

broad and floppy
low
narrow and frigid
high

Question 9

T/F the tonotopic encoding of sound only occurs at the level of the cortex

Answer 9

False, tonotopic organisation begins at the basilar membrane

Question 10

What does the organ of corti consist?

Answer 10

basilar membrane
inner and outer hair cells
tectorial membrane

Question 11

What is found on top of the hair cells?

Answer 11

Stereocilia

Question 12

What is the name of the tallest stereocilia

Answer 12

kinocilium

Question 13

How is sound transduced into a neural signal?

Answer 13

sound wave causes movement of basilar membrane, which generates a shearing force along with tectorial membrane. The physical pulling on the hair cell channels leads to K+ dependent Ca+ influx, and neurotransmitter release

Question 14

T/F K+ Channels are usually closed

Answer 14

False, they are partially open to create resting membrane potential

Question 15

T/F the alternating pattern of depolarisation and hyperpolarisation is asymmetric

Answer 15

True, hyperpolarisation is much smaller. Hair cells tend to want to depolarise in the direction of kinocilium

Question 16

What is the function of stria vascularis

Answer 16

it creates the K+ gradient between endolymph and perilymph

Question 17

What is the function of inner hair cell?

Answer 17

they depolarise 95% of the afferent nerves going to the brainstem

Question 18

What is the function of outer hair cell?

Answer 18

they provide efferent signals from superior olivary complex and amplify the movement of basilar membrane

Question 19

Depolarisation causes OHC to ________

Hyperpolarisation causes OHC to _______

Answer 19

contract

elongate

Question 20

what happens if we don’t have functional OHC?

Answer 20

basilar membrane movement can be 100x less

Question 21

T/F Aminoglycoside can affect the function of OHC

Answer 21

True, gentamicin is ototoxic, so we need to always monitor the amount of drug taken

Question 22

the primary auditory neuron is a bipolar neuron. Which two locations does it project to?

Answer 22

dorsal cochlear nucleus, which then projects upward

ventral cochlear nucleus, which then projects to superior olive

Question 23

What is the name of the auditory ascending tract? Which structure does it pass? which structure does this secondary neuron terminate at?

Answer 23

lateral lemniscus
inferior colliculus
medial geniculate nucleus

Question 24

Which area in the brainstem is responsible for localisation of sound? What does this complex consist?

Answer 24

the superior olivary complex

lateral and medial superior olives
trapezoid body

Question 25

What is the function of medial superior olive?

Answer 25

localisation of sound by time delay

Question 26

What is the function of lateral superior olive?

Answer 26

localisation of sound by intensity difference

Question 27

How do we localise sound by time delay

Answer 27

sound wave travels to the two ears at different time. The ear that’s closer to the sound origin will fire AP before the other ear. Both sides fire AP towards a series of neurons in MSO. At one point, one neuron will receive both signals at the same time, and this neuron may have deviated from the centre, hence direction of sound can be determined

Question 28

In localisation by intensity, one neuron will project to two areas of superior olive. What are the two areas?

Answer 28

ipsilateral LSO and contralateral medial nucleus of trapezoid body (MNTB)

Question 29

How does intensity of sound help sound localisation?

Answer 29

the relative amount of excitation from LSO and inhibition from MNTB will determine where the sound is

There is more excitation on the neuron that’s stimulated first

Question 30

What is the auditory cortex also known as?

Answer 30

Herschls gyrus

Question 31

T/F there is symmetrical representation of sound on both auditory cortices

Answer 31

False, different sounds can be lateralised
music is lateralised to the right
speech is isolated to the left