Hi Sarah,

The resting potential of a neuron is established by the active transport done by the Na/K pump. It is not the most stable state because you are expending energy to maintain this "resting" state (making it kind of a misnomer).

It's almost like a dam. When you open Na channels, they follow the electrochemical gradient down via passive diffusion.

This will depolarize the cell and make it favorable for the K+ to diffuse out, also passively, along its concentration gradient.

So in short, the active establishment of the electrochemical gradient by the Na/K pump allows for passive diffusion of Na+ and K+ during action potential.

I hope this helps,

Katt