How does action potential travel down an axon?

(Original post by loukas2993)
My answer depends on whether you are concerned about action potential propagation along an unmyelinated or a myelinated axon. Since you didn't specify anything about myelination or saltatory conduction, I will assume you meant an unmyelinated axon:

An action potential is generated at the axon hillock and is propagated in one direction, from the cell body towards the axon terminals, along the axon. During an action potential, the inside of the cell membrane becomes positively charged with respect to the outside. This action potential generates local currents that tend to depolarise the membrane patch immediately adjacent to the action potential. When depolarisation is sufficiently strong and reaches threshold, a new action potential is produce adjacent to the original one. This action potential is propagated in one direction only because the recently depolarised area of membrane is in absolute refractory period and cannot generate an action potential.

Please review this animation, I think you'll find it very useful in understanding the propagation of an action potential along an unmyelinated axon:

http://highered.mheducation.com/site...ated_axon.html

If you want more information on action potential propagation in a myelinated neuron, please just let me know.

Hope this helps.