Potassium, sodium, chlorine, and calcium ions in nerve cells have osmotic and electrostatic forces acting on them. Normally they can’t cross the cell membrane, but when ion channels open they rush into/out of the cell trying to reach osmotic equilibrium, and carrying their charge with them. This changes the cell’s voltage with respect to the environment; this is how the neuron fires.
The tendency of these ions to flow is actually a chemical effect, not an electrical one: osmosis is the primary driver. But the tendency to flow in this way can be quantified and calculated exactly like a voltage difference across very high resistance. Even though the ions want to flow to equalize this so-called voltage differential, ordinarily they can’t.
It’s potential potential, in the fullest physics sense of both words.
BWAHAHAHAHAHAHAHAHAHAHAHAHA! I love cognitive science.
upd 8 nov: revised first para, sorry for bumping everyone’s rss feeds