Question

What other action potentials do organisms use? Humans use the potassium and sodium. Is there any other chemicals used for an action potential?

Answer 1

i know some organisms use chlorine ions. i think algae and maybe others too, but your right that sodium and potassium are most important in animals

Answer 2

Calcium ions in cardiac action potential.
http://en.wikipedia.org/wiki/Cardiac_action_potential