Resting & Action Potentials in Neurones (4.1.2)

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What is a polarised membrane?
Where there's a slight charge difference between the inside and outside of the membrane.
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Describe how the resting potential is achieved.
The Na+/K+ pump uses ATP to pump 3Na+ out and 2K+ in. Other K+ protein channels are open and so some of K+ diffuses back out. There are many large anions inside the neurone that can't diffuse out. The gated Na+ channels are closed.
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What is the resting potential for most neurones?
Around -60mV.
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How is an action potential created?
When a sensory neurone is stimulated, some of the gated Na+ channels open due to energy changes caused by the stimulus. Na+ ions diffuse in quickly. This causes a charge reversal across the membrane. Membrane is depolarised.
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What needs to happen to result in an action potential?
A threshold level of Na+ must move into the membrane. The p.d must reach +40mV.
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How does the action potential move along?
The change in p.d across the membrane then causes voltage-gated Na+ channels to open. They open in response to a change in voltage when the Na+ ions move in. This will continue all the way along the neurone.
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What is the all or nothing rule?
All action potentials are the same size. But if the threshold potential of +40mV isn't reached then an action potential won't result.
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How does the neurone membrane recover?
Voltage-gated K+ channels open. K+ ions diffuse out of membrane. This starts to repolarise the membrane. Too many K+ diffuse out- hyperpolarisation. The Na+/K+ pump compensates for this and resting potential is restored.
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Card 2

Front

Describe how the resting potential is achieved.

Back

The Na+/K+ pump uses ATP to pump 3Na+ out and 2K+ in. Other K+ protein channels are open and so some of K+ diffuses back out. There are many large anions inside the neurone that can't diffuse out. The gated Na+ channels are closed.

Card 3

Front

What is the resting potential for most neurones?

Back

Preview of the front of card 3

Card 4

Front

How is an action potential created?

Back

Preview of the front of card 4

Card 5

Front

What needs to happen to result in an action potential?

Back

Preview of the front of card 5
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