Action Potentials 2

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Action Potentials


The action potential moves along the neurone.


  1. When an action potential happens, some of the sodium ions that enter the neurone diffuse sideways.
  2. This causes sodium ion channels in the next region of the neurone to open and sodium ions diffuse into that part.
  3. This causes a wave of depolarisation to travel along the neurone.
  4. The wave moves away from the parts of the membrane in the refractory period because these parts can’t fire an action potential.


The refractory period produces discrete impulses


  1. During the refractory period, ion channels are recovering and can’t be opened.
  2. So the refractory period acts as a time delay between one action potential and the next. This makes sure that action potentials don’t overlap but pass along as discrete (separate) impulses.
  3. The refractory period also makes sure action potentials are unidirectional (they travel in one direction).


Action potentials have an All – or Nothing Nature


Once the threshold is reached, an action potential will always fire with the same change in voltage, no


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