Speed of Conduction of Nerve Impulses (4.1.2)

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What does the speed of an A.P depend on?
The diameter of the neurone and whether or not it is myelinated.
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What does having a wide axon do to the impulse?
It speeds up the transmission- less resistance to the setting up of localised electrical circuits.
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How many of the peripheral neurones in vertebrates are myelinated?
About 1/3.
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How does myelination speed up action potentials?
Myelin sheath- an electrical insulator, ions can't move in & out of membrane where it's present. Depolarisation only occurs at nodes of Ranvier. Local circuits set up spread from node to node. The A.P jumps to nodes- v. quick, saltatory conduction.
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How much does myelin sheath speed up the action potential?
By about 50X.
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What are myelinated neurones used for?
Carry nerve impulses from sensory receptors to CNS and from CNS to effectors. They work over fairly long distances.
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What are non-myelinated neurones used for?
They are shorter and carry nerve impulses over shorter distances. They are used in coordinating body functions such as breathing.
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Card 2

Front

What does having a wide axon do to the impulse?

Back

It speeds up the transmission- less resistance to the setting up of localised electrical circuits.

Card 3

Front

How many of the peripheral neurones in vertebrates are myelinated?

Back

Preview of the front of card 3

Card 4

Front

How does myelination speed up action potentials?

Back

Preview of the front of card 4

Card 5

Front

How much does myelin sheath speed up the action potential?

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