10.3 The Nerve Impulse

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  • Created by: Molly
  • Created on: 10-03-14 11:44
What is a nerve impulse?
A self propagating wave of electrical disturbance that travels along the axon membrane.
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What are the two 'states' in which a cell can be?
Resting potential and action potential.
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How is the movement of Na+ and K+ across the axon cell membrane controlled?
Phospholipid bilayer with instrinsic proteins such as the sodium/potassium pump, sodium gated channel, potassium gated channel.
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How does the sodium potassium pump work?
It actively transports (against own gradient, requires ATP) potassium in to the axon and sodium out of the axon.
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In resting potential, what is the charge inside and out of the membrane?
Inside - negatively charged. Outside - positively charged.
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When in resting potential, the axon is...
Polarised.
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What is actively transported out of the axon via the sodium/potassium pump?
Sodium.
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How many sodiums are actively transported compared to potassiums?
3 sodiums out for every 2 potassiums in.
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Describe the electrical gradient.
As more sodiums move out of the axon the outside becomes positively charge, meaning the inside of the membrane is negative. Because potassium is also + charged, it is attracted to the inside of the axon and so it is harder for potassium to move out.
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What happens when a stimulus is received by a receptor or nerve ending?
Its energy causes a temporary reversal of charges on the axon membrane.
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What is the charge inside the membrane at resting potential and action potential?
At resting potential = -65mV, at action potential = +40mV
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In action potential, the membrane is said to be...
depolarised
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What happens to the sodium gated channel when a nerve impulse arrives at the end of the axon?
It causes the sodium gated channels to open and as a result sodium diffuses into the axon.
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What happens to the charge inside the membrane when there is a nerve impulse?
There is a reversal in the potential difference and the inside of the membrane becomes positively charged whilst the outside of the membrane is negatively charged.
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What happens when an action potential of +40 is achieved?
The sodium gated channels close and the potassium ion channels open allowing potassium to diffuse in. This causes REPOLARISATION of the axon.
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What is hyperpolarisation?
There is a temporary overshoot in the electrical gradient when the potassium ion channels open following an action potential, where the inside of the membrane becomes more negative than it needs to be. As a result the potassium channels now closes.
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Card 2

Front

What are the two 'states' in which a cell can be?

Back

Resting potential and action potential.

Card 3

Front

How is the movement of Na+ and K+ across the axon cell membrane controlled?

Back

Preview of the front of card 3

Card 4

Front

How does the sodium potassium pump work?

Back

Preview of the front of card 4

Card 5

Front

In resting potential, what is the charge inside and out of the membrane?

Back

Preview of the front of card 5
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