Generating an action potential


Generating an action potential


  • Sensory receptors act as transducers.
  • At resting state, Na/K ion pumps move ions in and out of the cell
  • A stimulus is detected by receptor cells, which convert this energy into an electrical impulse.
  • A bigger stimulus excites the membrane more.
  • A big enough stimulus will produce a  generator potential above the threshold level (approx. -55mV)


  • Various forms or energy received by sensory receptors are converted into electrical energy.
  • The resting potential is at -70mV (the inside is negatively charged) at resting state.
  • This excited the cell membrane, allowing it to become more permeable and ions to move more freely in and out of the cell, altering the potential difference (generator potential).
  • There is a bigger movement of ions, a bigger change is potential difference and a bigger generator potential in produced.
  • If the threshold is reached, the generator potential will trigger an action potential .

Overall summary

So a stimulus can only bring about a change if the generator potential is big enough to initiate an action potential, by reaching the threshold level of around -55mV.


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