Biology revision A2

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  • Created by: Elena
  • Created on: 08-05-14 11:33
What is a resting potential?
Potential difference or voltage across the neurone cell membrane while the neurone is at rest. It's about -60mv inside the cell compared with the outside
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Where are the sodium-potassium pumps? and what do they do?
In the plasma membrane - actively transport 3 sodium ions out of the cell for every 2 potassium ions they pump in the cell.
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Where are the voltage-gated sodium channels? And what do they do?
Surafce membrane - opens when receptor detects an energy change, energy is converted into electrical energy - causes them to open and an influx of sodium ions occurs - cause voltage in cell to increase (depolarisation)
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What is depolarisation?
Loss of polarisation across a membrane - when the membrane loses it's resting potential
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When does depolarisation occur?
When the voltage-gated sodium ions channels open and there is an influx of sodium ions which causes the voltage inside the cell to increase, which is depolarisation.
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What is the value of the Threshold potential?
-50mv
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What is the value of the Action potential?
+40mv
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What is the value of the Resting potential?
-60mv
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What will happen if depolarisation reached -50mv (threshold potential)?
An action potentail would be generated
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What happens when an action potential occurs?
All sodium channels close at +40mv, and the voltage-gated potassium channels open and potassium ions move out of the neurone by facilitated diffusion - causes potential difference in cell to drop again (repolarisation) until a voltage of around -70mv
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How do the potassium ions move out of the cell during an action potential?
Facilitated diffusion
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What is repolarisation?
When the potential difference inside the cells drops again - after the action potential occurs - once potssium ions are diffused out of the neurone
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What is hyperpolarisation?
When the potential across the membrane drops even further that the resting potential (which is -60mv) at around -70mv - after repolarisation
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What is the refractory period?
The short period of time after firing during which it is more difficult to stimulate a neurone - allows particular point in membrane to have a recovery time W
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What are voltage-gated channels?
Channels in the cell membrane that allow the passage of charged particlesor ions. Have a mechanism called a gate which can open & close the channel. Gates respond to changes in the potential difference across membrane
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What are local currents?
Movements of ions along the neurone - flow of ions is caused by an increase in conc at one point - causes diffusion away from region of higher conc
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Where do local currents occur?
In the cytoplasm of the neurone
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What do the local currents make happen?
It causes sodium ion channels further along the membrane to open
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Other cards in this set

Card 2

Front

Where are the sodium-potassium pumps? and what do they do?

Back

In the plasma membrane - actively transport 3 sodium ions out of the cell for every 2 potassium ions they pump in the cell.

Card 3

Front

Where are the voltage-gated sodium channels? And what do they do?

Back

Preview of the front of card 3

Card 4

Front

What is depolarisation?

Back

Preview of the front of card 4

Card 5

Front

When does depolarisation occur?

Back

Preview of the front of card 5
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