Properties Of Sound And The Trasnmisstion Of Auditory Signals

Question 1

What is sound?

Answer 1

A pressure wave with areas of compression and rarefaction

Question 2

What frequency are human speech

Answer 2

500 to 3000 hetz

Question 3

What freqencies can humans hear

Answer 3

20 to 20 KHz

Question 4

What’s is sound pressure level

Answer 4

Lp is RMS of sound pressure in N/m2 divided add diagram

Question 5

Is the decibel scale a linear scale if not what is it?

Answer 5

No it is log 10 scale

Question 6

List the peripheral machisms of the auditory system

Answer 6

1.outerear
2. Middle ear
3.inner ear
4. 8th cranial nerve

Question 7

What is the central machismo of the auditory system?

Answer 7

Brain, specifically the coccular nucleus

Question 8

How does sound get transduced from the ear drum to the oval window?

Answer 8

1. Ear drum (tympanum)
2. Malleus
3. incus
4. Stapes
5. oval window

Question 9

What is place theory?

Answer 9

It states that each position on the basilar membrane has a characteristic frequency at which it has maximum vibration amplitude.

Question 10

In place theory, where along the basilar membrane would you be more likely to have a high amplitude of vibration for high frequencies ? Why?

Answer 10

Towards the base of the basilar membrane as it is thin and stiff.

Question 11

In place theory, where along the basilar membrane would you be more likely to have a high amplitude of vibration for low frequencies ? Why?

Answer 11

Towards the apex (middle of the loop) as the basilar membrane is wide and floppy.

Question 12

How many types of hair cells do we have, which are linked to auditory nerve fibers?

Answer 12

We have two types of hair cells, outer hair cells and inner hair cells, only the inner hair cells are linked to auditory nerve fibres.

Question 13

What is the purpose of outer hair cells

Answer 13

They are used to amplify vibrations to inner hair cells.

Question 14

How do the tectorial membrane and the outer hair cells work to transmit vibrations to the inner hair cells?

Answer 14

They are mechanically connected, the tectorial membrane contacts both hair cell types

Question 15

How do inner hair cells produce ap

Answer 15

Vibration of the oval window vibrates the cochlear fluid
This vibrates the inner hair cells and this opens ion channels, which causes a depolarisation and this opens vgnc and leads to an ap

Question 16

How do outer hair cells amplifiy the vibrations that reach the inner hair cells

Answer 16

Basilar membrane vibrate (look up in text book) this causes the vibration of outer hair cells which amplifiy these signals (by contacting )

Question 17

How does the intercellular voltage of the innerhair cell change with increasing frequency?

Answer 17

Low frequency voltage copies the signal, as frequency increases the AC signal get superposed with a DC components at frequency’s above 3-5b KHz there is mostly just a DC component.

Question 18

How is the frequency coded for in the auditory nerve when the inner hair cells are stimulated with a sinosidal wave below 5 KHz?

Answer 18

The response is dominated by spikes in phase with the signal but only during one half of the cycle the signal is half rectified.

Question 19

How high can auditory nerve perform temporal coding?, how can this number be achieved?

Answer 19

About 4KHz but each ap spike takes about 2 ms hence only 500 Hz can be done by each cell so it us shared out over several cells.(check text book)

Question 20

What do we mean when we say that auditory fibres have a tuning curve?

Answer 20

A auditory fibre is measured a threshold of firing is measured for that fiber, it turns our that there is alway a frequency at which this fiber is most sensitive this is the charactaraistic frequency of the fibre

Question 21

List the path of the auditory system from the auditory nerve to the primary auditory cortex

Answer 21

1. Auditory nerve
2. Cochlear nucleus
3. Superior olivary nuclei
4. Inferior colliculus
   5.medial geniculate nucleus
5. Primary auditory cortex.

Question 22

What happened to the ability of a nerve to transmit an ap when it is over exposed to noise

Answer 22

It decreases

Question 23

Name one machism that leads to the loss of an audioty nerve to transmit ap

Answer 23

Loss of myolin, both increasing the proportion of node to myalin and the thickness of myelin

Question 24

What happens to cellular activity in the dorsal Claudette nucleus when an animal has an over exposure to noise?

Answer 24

There is an increase in DCN neuronal activity

Question 25

What happens to gap induced pre pulse inhibition of the audcousic startle response when there is tinnitus and why?

Answer 25

The tinnitus blocks the ability of the animal to sense the gap so there is a loss of the pre pulse inhibition.

Question 26

What type of neuronal activity is seen in DCN fusiform cells when there is an over exposure to noise

Answer 26

They show a higher propscity for burst firing

Question 27

What happens to LTP in acoustic neurones after acetic over exposure?

Answer 27

It ablosises long term potentiation

Question 28

How does mangiest tehronate effect ltp in over exposed neurones

Answer 28

It re-established LTP