3: Permeability is key!

So there are two opposing gradients affecting membranes: one for concentration, and one for voltage. But, and this is a big BUT:

The gradients only have an effect IF ions can move through the membrane. If you put a brick wall in place of the membrane, you could have all sorts of differences in concentration and voltage, but those differences won’t have any effect in the real world. A membrane with no open channels is actually a lot like a brick wall.

closed channels: open channels:
closed channels open channels


We’ll see how this plays out in the equations soon…