The Nerve Impulse

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The nerve impulse is described as a self propagating wave of electrical disturbance which travels along the surface of the axon membrane.

It is a temporary reversal of the potential difference across the membrane, switching from the resting potential to the action potential.

The resting potential

The resting potential of the cell is maintained due to the different concentrations of sodium and potassium ions. Both of these ions are positive.

  • The phospholipid bilayer is impermeable to both ions, and prevents either one from diffusing naturally through it
  • The membrane is dotted with intrinsic proteins that travel all the way from the outside in. These proteins act as channels and can allow the sodium and potassium. However, some of the gates are 'gated' and will only only certain ions to move in certain directions across chemical and electrical gradients.
  • Some proteins actively transport ions through the membrane, against their electro-chemical gradients. This requires ATP from respiration. These gates are called sodium potassium pumps

The operation of these mechanisms…


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