Edit 5th September 2011:
Note there is a small error at around 2:20. The movement of ions to correct hyperpolarisation occurs by active transport using the sodium-potassium pumps (purple block) rather than by diffusion as the narration states. Thanks to user SirBlibofDoh for pointing this out.
The action potential for A level biology.
Produced as part of a final year undergraduate project into the use of podcasting in education at the University of Sussex.