Hearing - Hair cells

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  • Created by: Jess
  • Created on: 15-05-14 12:09
What is the transduction mechanism in hearing?
Bending of the hairs.
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How are hair cells connected to the CNS?
By sprial ganglion neurons (bipolar cells).
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What percentage of sensory fibres innervate the single inner row of hair cells?
90% (roughly 10 sensory fibres per hair cell)
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Why is the shape of the basilar membrane important?
It is narrower close to the oval window. Important consequences in detecting pitch. Narrower - high frequency. Wider - low frequency.
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What neurotransmitter is constantly released from the base of hair cells at a low rate?
Glutamate.
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What happens when the hair cells bend towards the kinocillium?
Increase open prob of voltage gated Ca channels, increases glutamate release, increases firing rate in the afferent nerve.
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What happens when the hair cells bend away from the kinocillium?
Decreases open prob of voltage gated Ca channels, decrease glutamate release, decreases firing frequency in the afferent nerve.
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What polarity are the hair cells at rest?
Depolarised (-60mV)
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How are hair cells mechanically tuned?
Hair bundle length vaires due to efferent stimulation by motor nerves.
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What is hair cell tuning influenced by?
The location in the cochlea, the length of stereocillia and electrical tuning.
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Why does ionic movement have to be through the hair cells?
Tight junctions between cells prevents ionic movement elsewhere.
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Describe the K gradient through a hair cell.
K is at a very high concentration at the top of the cell and a low concentration at the bottom. This affects ionic flux.
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Explain how membrane potential changes are produced in hair cells.
K influx causes depol, opens voltage gated Ca channels - Ca influx, opens Ca sensitive K channels and K leaves through bottom of cell with its gradient, causes hyperpol, opens more K channels causing more K exit, Ca pumped out to return to normal.
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What type of membrane potential changes are seen in hair cells?
Oscillatory/Sinusoidal.
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Hair cells release glutamate, what does this regulate?
Firing in the cochlear nerve.
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Card 2

Front

How are hair cells connected to the CNS?

Back

By sprial ganglion neurons (bipolar cells).

Card 3

Front

What percentage of sensory fibres innervate the single inner row of hair cells?

Back

Preview of the front of card 3

Card 4

Front

Why is the shape of the basilar membrane important?

Back

Preview of the front of card 4

Card 5

Front

What neurotransmitter is constantly released from the base of hair cells at a low rate?

Back

Preview of the front of card 5
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