Properties Of Sound And The Trasnmisstion Of Auditory Signals Flashcards
What is sound?
A pressure wave with areas of compression and rarefaction
What frequency are human speech
500 to 3000 hetz
What freqencies can humans hear
20 to 20 KHz
What’s is sound pressure level
Lp is RMS of sound pressure in N/m2 divided add diagram
Is the decibel scale a linear scale if not what is it?
No it is log 10 scale
List the peripheral machisms of the auditory system
1.outerear
2. Middle ear
3.inner ear
4. 8th cranial nerve
What is the central machismo of the auditory system?
Brain, specifically the coccular nucleus
How does sound get transduced from the ear drum to the oval window?
- Ear drum (tympanum)
- Malleus
- incus
- Stapes
- oval window
What is place theory?
It states that each position on the basilar membrane has a characteristic frequency at which it has maximum vibration amplitude.
In place theory, where along the basilar membrane would you be more likely to have a high amplitude of vibration for high frequencies ? Why?
Towards the base of the basilar membrane as it is thin and stiff.
In place theory, where along the basilar membrane would you be more likely to have a high amplitude of vibration for low frequencies ? Why?
Towards the apex (middle of the loop) as the basilar membrane is wide and floppy.
How many types of hair cells do we have, which are linked to auditory nerve fibers?
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.
What is the purpose of outer hair cells
They are used to amplify vibrations to inner hair cells.
How do the tectorial membrane and the outer hair cells work to transmit vibrations to the inner hair cells?
They are mechanically connected, the tectorial membrane contacts both hair cell types
How do inner hair cells produce ap
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
How do outer hair cells amplifiy the vibrations that reach the inner hair cells
Basilar membrane vibrate (look up in text book) this causes the vibration of outer hair cells which amplifiy these signals (by contacting )
How does the intercellular voltage of the innerhair cell change with increasing frequency?
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.
How is the frequency coded for in the auditory nerve when the inner hair cells are stimulated with a sinosidal wave below 5 KHz?
The response is dominated by spikes in phase with the signal but only during one half of the cycle the signal is half rectified.
How high can auditory nerve perform temporal coding?, how can this number be achieved?
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)
What do we mean when we say that auditory fibres have a tuning curve?
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
List the path of the auditory system from the auditory nerve to the primary auditory cortex
- Auditory nerve
- Cochlear nucleus
- Superior olivary nuclei
- Inferior colliculus
5.medial geniculate nucleus - Primary auditory cortex.
What happened to the ability of a nerve to transmit an ap when it is over exposed to noise
It decreases
Name one machism that leads to the loss of an audioty nerve to transmit ap
Loss of myolin, both increasing the proportion of node to myalin and the thickness of myelin
What happens to cellular activity in the dorsal Claudette nucleus when an animal has an over exposure to noise?
There is an increase in DCN neuronal activity
