depolarisationen

Depolarisationen are changes in the membrane potential of a cell in which the inside of the cell becomes less negative (more positive) relative to the outside. They are a central feature of electrical signaling in many excitable cells, including neurons, cardiac muscle cells, and skeletal muscle fibers. A depolarisation can be subthreshold, contributing to graded potentials, or large enough to trigger an action potential when a critical threshold is reached.

In neurons, the resting membrane potential is typically around -70 mV. A depolarising stimulus opens voltage-gated or ligand-gated ion channels, most notably sodium (Na+) channels, allowing Na+ to rush into the cell. This inward current reduces the negative interior potential and drives it toward the positive; if the depolarisation reaches a threshold (often around -55 mV), an action potential is generated. The rapid upstroke of the action potential is mainly due to a further opening of Na+ channels; the peak is followed by repolarisation as voltage-gated potassium (K+) channels open and K+ exits the cell, sometimes with a brief hyperpolarisation before the resting potential is restored by ion pumps and leaks.

Depolarisationen play a role in synaptic transmission (excitatory postsynaptic potentials), muscle contraction, and the propagation of electrical signals along axons and muscle fibers. Abnormal depolarisation patterns can be associated with neurological or cardiac disorders, reflecting altered ion channel function, transporter activity, or membrane integrity. Terminology varies by language, with depolarisation/depolarization used in different dialects.