Action Potential

• How does the action potential move along the neurone?


  As a wave of depolarisation
• What do some of the sodium ions do when an action potential happens?

  Some of the sodium ions that enter the neurone diffuse sideways

  • This causes sodium ion channels in next region of neurone to open = sodium ions diffuse into that part
  • causes a wave of depolarisation to travel along the neurone
• what does the wave move away from?

  the parts of the membrane in the REFRACTORY PERIOD because these parts cannot fire an action potential
• what does the refractory period produce?


  discrete impulses
• what happens during the refractory period?

  ion channels are recovering and cannot be opened
• what does the refractory period act as ?


  a time delay between one action potential and the next

  • this means that
• the refractory period acts as a time delay between one action potential and the next. this means that.?


  • action potentials dont overlap, but pass along as discrete (separate ) impulses
  • theres a limit to the freq at which the nerve impulses can be transmitted
  • action potentials are unidirectional - only travel in one direction
• give one property of action potentials?


  they do not overlap, but pass along as discrete impulses
• give another property of action potentials?

  there is a limit to the frequency at which the nerve impulses can be transmitted
• give another property of action potentials?

  Action potentials are unidirectional
• what does unidirectional mean?


  only travel in one direction
• what does discrete mean in the case of discrete impulses?

  separate impulses
• what nature do action potentials have?


  An all-or-nothing nature
• What happens once the THRESHOLD IS REACHED?


  An action potential will always fire with the same change in voltage, no matter how big the stimulus is
• what happens if the threshold is not reached?


  An action potential will not fire This is the all-or-nothing nature of action potentials
• What will a bigger stimulus cause?

  • WILL NOT CAUSE a bigger action potential
  • WILL CAUSE them to fire more frequently