The Action Potential:  Images

These following images should help you to see how the action potential moves along the axon's membrane.  Take a look at the animated figure (16 k) which includes these imagese in motion (it may not work on all web browsers) .

animation frame 1 At rest, the inside of the neuron is slightly negative due to a higher concentration of positively charged sodium ions outside the neuron. 
animation frame 2 When stimulated past threshold, sodium channels open and sodium rushes into the axon, causing a region of positive charge within the axon. 
animation frame 3 The region of positive charge causes nearby sodium channels to open. Just after the sodium channels close, the potassium channels open wide, and potassium exits the axon. 
animation frame 4 This process continues as a chain-reaction along the axon.  The influx of sodium depolarizes the axon, and the ourflow of potassium repolarizes the axon. 
animation frame 5 The sodium/potassium pump restores the resting concentrations of sodium and potassium ions 


   
      copyright (c) 2008 Michael R. Markham Updated: April 25, 2008