想请教人体生理学问题

Action potential is the transient and rapid change in the membrane potential that spread rapidly all over the cell membrane.
Action potentials usually occur because of increases in the conductance of Na+ or Ca2+.

Mechanisms for production of AP
At the onset of the action potential (threshold), the Na+ channels instantaneously become activated
Na+ inflow - depolarization
Na+ channels close and K+ channels open:
K+ out flow – repolarization
Na+-K+ pumps re-establish K+ and Na+ gradients.

人民卫生出版社《生理学》教材，我记得好像刚开篇就是讲电生理的