Transmission of action potentials

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  • Created by: Steff06
  • Created on: 19-05-16 13:26
What are local currents?
The movements of ions along the neurone. The flow of ions is caused by an increase in concentration at a point, which causes diffusion away from the region of higher concentration.
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What is the effect of the opening of sodium ion channels?
The balance of sodium and potassium ions created by the sodium/potassium pumps is upset.
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What does this create and where in the neurone?
Creates local currents in the cytoplasm of the neurone.
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What do the local currents cause?
Cause sodium ion channels further along the membrane to open.
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Describe the production of a local current (steps 1-3)
When an action potential occurs, the sodium ion channels open at a point along the neurone. Sodium ions diffuse across the membrane from high conc outside to inside the neurone. This movement upsets the balance of ions.
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Describe steps 4-6
The conc of sodium ions inside the neurone rises where the Na+ channels are open. Causes sodium ions to diffuse sideways, away from region of increased concentration. Movement of charged particles is local current.
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Where are the voltage-gated sodium channels and how are they operated?
Further along the membrane. They are operated by changes in voltage across the membrane.
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What is the voltage across the membrane at rest and what is this known as?
-60mV. This is the resting potential.
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What does the movement of sodium ions along the neurones alter?
Alters the potential difference across the membrane.
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What do the gates do when the potential difference across the membrane is reduced?
The gates open.
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What is the effect of the gates opening?
The sodium ions can enter the neurone at a point further along the membrane.
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What is the myelin sheath?
A insulating layer of fatty material.
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What cannot diffuse through this fatty layer?
Sodium and potassium ions.
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What are the gaps in the myelin sheath?
Gaps between the Schwann cells known as nodes of Ranvier
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Where do the ionic exchanges occur in a myelinated neurone?
Only occur at the nodes of Ranvier.
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How do the sodium ions diffuse in a myelinated neurone?
Diffuse along the neurone from one node of Ranvier to the next.
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What does the action potential appear to do?
Action potential appears to jump from one node to the next.
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What is this 'jumping' known as?
Saltatory conduction.
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What are the advantages of saltatory conduction?
Transmission is sped up as action potentials can only occur at nodes of Ranvier.
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Other cards in this set

Card 2

Front

What is the effect of the opening of sodium ion channels?

Back

The balance of sodium and potassium ions created by the sodium/potassium pumps is upset.

Card 3

Front

What does this create and where in the neurone?

Back

Preview of the front of card 3

Card 4

Front

What do the local currents cause?

Back

Preview of the front of card 4

Card 5

Front

Describe the production of a local current (steps 1-3)

Back

Preview of the front of card 5
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