leak channel

A leak channel is a tiny pore in a neuron's outer skin (its membrane) that stays open all the time, quietly letting certain charged atoms, called ions, slip through. Most other channels in the membrane behave like doors with a lock: they snap open only when the cell flips a switch, such as a change in voltage or the arrival of a chemical messenger. A leak channel has no lock and no switch. It simply sits there, propped open, day and night. Because of that constant openness, it sets the membrane's resting leakiness, the steady background trickle of ions that never stops.

The vast majority of leak channels are picky in one important way: they let potassium ions through far more easily than any other kind. Potassium is more crowded inside the cell than outside, so given an always-open door, it tends to dribble outward. Each potassium ion carries a tiny positive charge, so this slow outward leak pulls positive charge out of the cell and leaves the inside slightly negative compared with the outside. That gentle, steady negativity is the resting membrane potential, the cell's electrical idling point. It is the baseline the neuron springs away from when it finally fires an action potential, the brief electrical pulse it uses to signal.

So although a leak channel does nothing dramatic on its own, it is the quiet anchor of a neuron's electrical life. By holding the resting voltage steady, it keeps the cell poised and ready, neither asleep nor firing, so that when a real signal arrives the neuron can respond crisply and then settle right back to where it started.