Hyperpolarization

Hyperpolarization is a change in a cell's membrane potential that makes it more negative. It is the opposite of a depolarization. It inhibits action potentials by increasing the stimulus required to move the membrane potential to the action potential threshold.

Mechanism

Hyperpolarization is often caused by efflux of K+ (a cation) through K+ channels, or influx of Cl- (an anion) through Cl- channels. On the other hand, influx of cations, e.g. Na+, or efflux of anions will decrease membrane potential, leading to depolarization.

Role in Neurons

In neurons, hyperpolarization is often caused by efflux of K+ (a cation) through K+ channels, or influx of Cl- (an anion) through Cl- channels. This increase in K+ permeability leads to an increase in the magnitude of the membrane potential (i.e., hyperpolarization) because K+ is at a higher concentration inside the cell. This results in a net loss of positive charge, making the inside of the neuron more negative.

Role in Cardiac Cells

In cardiac cells, hyperpolarization is the main cause for the resting potential of these cells. It is also the cause of the absolute refractory period, a period of time during which the cell cannot initiate another action potential.

See Also

• Depolarization
• Action potential
• Membrane potential
• Neuron
• Cardiac cells