neuronal membrane

The neuronal membrane is the thin, flexible skin that wraps around a neuron — a nerve cell — and separates the watery soup inside the cell from the watery world outside it. Imagine a soap bubble made of two layers of greasy molecules standing tail-to-tail: the oily tails huddle in the middle to hide from water, while the water-loving heads face outward toward the wet on both sides. This double sheet is called a lipid bilayer (lipid just means fat-like), and it is only about two molecules thick, yet it is what holds the whole cell together and gives it a definite inside and outside.

On its own this fatty film would be a fairly boring, leaky barrier. What makes the neuronal membrane special is everything embedded in it: hundreds of different proteins float in the bilayer like ships and gates dotted across a calm sea. Some are tiny doorways called ion channels that let charged particles slip in or out; others are pumps that push those particles uphill, and still others are receptors that catch chemical messages from neighboring cells. Because these proteins control exactly what crosses and when, the membrane can build up an electrical difference between inside and outside and then fire it off as a signal. In short, the membrane is not just the neuron's wall — it is the stage on which nearly all of the neuron's electrical and chemical signaling takes place.