depolarisering

Depolarization, also spelled depolarisation or depolarisering in some languages, refers to the reduction or reversal of polarization in a system. The term is used across disciplines, with domain-specific meanings in physics, chemistry, biology and medicine. In broad terms it describes a move toward a less polarized state or toward a more uniform distribution of charge.

In physics and materials science: Polarization is the alignment of electric dipoles in a material under an external field, producing a net dipole moment. Depolarization occurs when the field is removed or reversed, and dipoles return toward random orientations. This relaxation process, called dielectric relaxation, can take from nanoseconds to seconds depending on the material and conditions.

In biology and medicine: In cells, depolarization denotes a decrease in the resting membrane potential, i.e., a shift toward a less negative value. It typically results from the opening of voltage-gated sodium channels and influx of Na+, generating an action potential in neurons and muscle fibers. After depolarization, repolarization occurs as potassium exits the cell, restoring the resting potential. In the heart, a coordinated wave of depolarization triggers contraction; clinical defibrillation aims to depolarize large populations of cells to reset rhythm.

In diagnostics and research, depolarization is used as a measurable signal in electrophysiology and in studies of the dielectric properties of materials. The concept emphasizes how charge distribution and membrane potential influence function in living systems and in engineered materials.