Membrane potential

Membrane potential is the voltage difference between a cell’s interior and exterior, produced by unequal ion distributions across its membrane. It can store electrical energy and drive ion movement and cellular signaling.

Nernst equation: An equation that relates an ion’s concentration gradient across a membrane to its equilibrium voltage. It predicts the voltage at which one ion’s chemical and electrical forces balance.
Lipid bilayer: A double layer of lipid molecules that forms the basic structure of cell membranes. Its low ion permeability lets charge accumulate on opposite sides.
Action potential: A rapid, transient change in a cell’s membrane voltage that propagates along an excitable membrane. Neurons and muscle cells use this voltage event to transmit signals.
Membrane current: The flow of electrical charge across a membrane, commonly carried by ions. Current is charge flow; membrane potential is the voltage that can drive or result from that flow.
Goldman–Hodgkin–Katz equation: An equation estimating membrane voltage from ion concentrations and relative membrane permeabilities. It extends the single-ion Nernst relation to membranes permeable to several ions.
Ion: An atom or molecule with a net electric charge from gaining or losing electrons. Charged particles, especially sodium, potassium, chloride, and calcium, generate membrane voltage.
Resting membrane potential: The relatively stable membrane voltage of a cell when it is not actively signaling. It is the baseline voltage from which many cellular electrical signals begin.
Equilibrium potential: The membrane voltage at which a particular ion has no net electrochemical movement. A single ion’s equilibrium voltage differs from the combined voltage of a permeable membrane.
Ion channel: A membrane protein that forms a selective pore through which ions can cross. Opening and closing channels changes ionic permeability and therefore membrane voltage.
Concentration gradient: A spatial difference in the concentration of a substance. Unequal ion concentrations across the membrane create chemical forces on ions.

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