depolarize

Depolarize, repolarize and hyperpolarize are terms used in electrophysiology to refer to changes in the membrane potential. Cells normally have a negative resting potential; they are "polarized". Depolarize: during an action potential, when the membrane potential is becoming less negative, the cell is depolarizing. Repolarize: during the repolarizing phase, the membrane potential becomes more negative. When a cell is more negative inside than the resting potential, it is hyperpolarized. The diagram below shows the membrane potential during a neuronal action potential. The action potential starts with a depolarizing phase then has a repolarizing phase. When the membrane potential is more negative than the resting potential (-60 mV) the cell is hyperpolarized. After the hyperpolarizing phase the membrane potential returns to the resting potential.