A self-propagating wave of electrical activity that travels along the axon of a neurone
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What are the two states of an axon?
Resting potential and action potential
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What is resting potential?
When a neurone is at rest, polarised and at -70mv
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Explain how the resting potential of an neurone is maintained
- Sodium-potassium pump actively transports 3Na+ ions out of the membrane into the surroudning tissue fluid and 2K+ into the axon cytoplasm - K+ protein channels open so K+ ions diffuse out of the axon - volatge-gated sodium channels are closed -->
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so overall the axon is less positive than the outside of the axon in the tissue fluid
-->
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What is an action potential?
Depolarisation of the axon membrane which creates a nerve impulse at +40mv
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What causes some voltage-gated sodium channels to open?
The energy of the stimulus detected by a receptor in the nervous system
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Where do Na+ ions then diffuse down their electrochemcial gradient?
Into the axon cytoplasm
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What does the opening of some voltage-gated sodium channels cause?
The opening of more voltage-gated sodium channels to open causing an influx of sodium ions into the axon cytoplasm
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Once the action potential fo around +40mv has been established what happens?
The voltage-gated sodium channels close preventing a further influx of Na+ ions
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Why do some voltage-gated potassium channels begin to open then?
So that K+ ions can diffuse out of the axon cytoplasm and repolarise the axon
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What does this outward movement of K+ ions cause?
A temporary overshoot of the electrcal gradient, with the inside of the axon being more negative than usual
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What is this occurence called?
Hyperpolarisation
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What now closes and what other protein comes into action?
Some voltage-gated potassium channels close and the sodium-potassium pump starts working once again, repolarising the axon back to a resting potential of -70mv
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Other cards in this set
Card 2
Front
What are the two states of an axon?
Back
Resting potential and action potential
Card 3
Front
What is resting potential?
Back
Card 4
Front
Explain how the resting potential of an neurone is maintained
Back
Card 5
Front
so overall the axon is less positive than the outside of the axon in the tissue fluid
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