A level Biology exam revision resources written by A level Examiners





 

Once an action potential occurs on a neurone membrane it automatically spreads along the membrane. This is because the depolarisation of one area causes an electrical circuit to be established which causes the adjacent voltage gated sodium channels to open. Which generates an action potential in the adjacent membrane.

The figure 8 sequence shows how an action potential occurs and spreads along the neurone

Figure 8
The following sequence shows how an action potential occurs and spreads along the neurone

Neurone that are surrounded by Schwann cells are said to be myelinated neurones. This is because the Schwann cells contain the fatty substance myelin. Myelin acts as an insulator and instead of the localised circuits forming, much larger circuits form between each node of Ranvier. The propagation of the action potential is a series of 'jumps' from node to node. This is called saltatory conduction and is much faster than the normal conduction sequence (approx 100 times faster).

The sequence in figure 9, shows saltatory conduction.

Figure 9 : Saltatory conduction
Figure 5 : Saltatory conduction

Flash Animation

Click here to run this simulation of Normal conduction Vs Saltatory conduction.

 click to run simulation




Share this knowledge

 
 



Back To Top Back To Top