Membrane Potential
The electrical potential difference across a biological cell membrane produced by asymmetric ion concentration gradients.
Governing formula
V_m = V_in - V_out (Resting Potential ≈ -70 mV)
SI unit
mV (Millivolts)
In depth
Maintained by active ATP-driven Na⁺/K⁺ pumps and selective potassium leak channels. Inside the cell is electrically negative (~-70 mV) relative to extracellular fluid, creating an electrochemical driving force for ion transport and cell signaling.
Examples in the real world
Resting membrane potential of -70 mV across giant squid axon cell membranes.