1. Details of Depolarization, Repolarization, and the Refractory Period
The Action Potential
Details of Depolarization, Repolarization, and the Refractory Period

2. The Action Potential: Depolarization Phase
What kind of Na+ channels are these and
where are they?
Ach
(At the motor end-plate)
What is the magnitude of the voltage change (on graph) required for this cell to generate the all-or-none Action Potential?

3. The Action Potential: Repolarization Phase
When is it possible to generate another Action Potential in this cycle? Explain why.

4. Unidirectional Propagation
Propagation of the action potential only moves in one direction, from the axon hillock to the axon terminals.
The region just recovering from an action potential (K+ outflow region) cannot be stimulated by local current flow.
During the repolarizing and undershoot phases, the inactivation gates of the Na+ channels are still closed, blocking any Na+ influx even if the activation gates were to open.
Why is this important?
Refractory Period