Resting Potentials and Active Potentials

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  • Created by: Ellegrace
  • Created on: 29-12-15 15:36

A Resting Neurone

  • When a neurone is not transmitting an action potential it is said to be at rest.
  • It is actively transporting ions across its plasma membrane.
  • Sodium/pottasium ion pumps use ATP to pump 3 sodium ions out for every 2 potasiums in.
  • Plasma membrane is more permeable to pottasium ions than sodium ions so many diffuse out again.
  • Interior of the cell is a negative potential compared to the outside.
  • The cell mambrane is said to be polarised.
  • Potential difference across the cell mambrane is -60mV.
  • This is called the resting potential. 

An Action Potential

  • At rest the gated sodium ion channels are kept closed.
  • the sodium/pottasium ion pump uses ATP to actively transport three sodium ions out for every 2 pottasium ions brought into the axon.
  • A few pottasium ions diffuse back out as some pottasium channels open
  • If some of the sodium ions channels are opened then sodium ions will quickly diffuse down their concentration gradient into the cell from the surrounding tissue fluid.
  • Causes a depolarisation of the membrane.
  • Generator region of the receptor cells the gated channels are open due to an energy change in the environment.
  • E.g. pressure change.
  • The gates further along the neurone are opened by changes in the potential difference across the membrane.
  • These are called voltage-gated channels.
  • Channels respond to depolarisations of the membrane.

All or Nothing

  • Generator potentials in the sensory receptor are depolarisations of the cell membrane.
  • A small depolarisation will have


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