11. What technique can be used to monitor channel activity? 12. What are the four different types of gated ion channels? 13. What is membrane potential and how is it maintained? 14. What is an action potential and how is it generated? Why is its movement across a nerve 15. Be prepared to describe the activation of an action potential at one end of a nerve cell in only one direction? cell (dendrite), its propagation towards the synapse, its conversion to a chemical signal at the synapse, and how this signal activates the post-synaptic cell..