Neurones

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  • Created by: Ribenas1
  • Created on: 04-03-17 14:52
What is the cell membrane at rest?
Polarised
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What does polarised mean?
Difference in charge (-called potential difference)
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What is the resting state?
Outside of the membrane positively charged than inside bc more positive ions outside
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How is the resting potential maintained?
Sodium potassium pumps + potassium ion channels
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Explain how the resting potential is maintained
1) Sod pot pumps move sod ions out - can't diffuse back in bc membrane isn't permeable to them = creates electrochemical gradient. Pumps move potassium ions in - membrane is permeable to them so diffuse back out through channels.
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What happens when membrane is stimulated?
Triggers sodium ion channels to open = rapid change in potential difference = causes A.P
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Explain process of membrane being depolarised
1) Stimulus - sod ion channels open = inside less negative. 2) Depolarisation - threshold more sodium ions channels open. more sodium ions rapidly diffuse in.
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Explain process of membrane being repolarised
3) Repolarisation - sodium ion channels close + pot ion channels open. Membrane more permeable = pot ions diffuse out = back to resting potential
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Explain process of hyperpolarisation
Pot ion channels slowly close = overshoot = potential difference become more negative than resting potential
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Explain process of resting potential after stimulation
ion channels reset - sodium pot pumps return to resting potential
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Stages of stimulus exciting a membrane
1) Stimulus 2) Depolarisation 3) Repolarisation 4) Hyperpolarisation 5) Resting potential
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What is the refractory period
ion channels recovering + can't be opened = time delay. A.P therefore don't overlap but pass as discrete impulses. Limits freq. @ which nerve impulses can be transmitted. A.P are uni directional
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What is 'All or nothing'
When the A.P is reached it fires a voltage, not reached = won't fire = all or nothing. Bigger stimulus = A.P fire more frequently
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What increases speed of A.P
1) Myelination - myelin sheath = faster 2) axon diameter - bigger = less resistance = faster 3) Temperature - ions diffuse faster - 40c denatures
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Other cards in this set

Card 2

Front

What does polarised mean?

Back

Difference in charge (-called potential difference)

Card 3

Front

What is the resting state?

Back

Preview of the front of card 3

Card 4

Front

How is the resting potential maintained?

Back

Preview of the front of card 4

Card 5

Front

Explain how the resting potential is maintained

Back

Preview of the front of card 5
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