Membranpotentialen

Membranpotentialen, also known as membrane potential, refers to the difference in electrical potential between the interior and exterior of a biological cell. This potential arises from the uneven distribution of ions across the cell membrane, primarily due to the selective permeability of the membrane and the action of ion pumps. Key ions involved include sodium (Na+), potassium (K+), chloride (Cl-), and calcium (Ca2+).

At rest, most cells maintain a resting membrane potential, which is typically negative inside relative to the outside. This is largely due to a higher concentration of potassium ions inside the cell and a greater permeability to potassium ions compared to sodium ions. The sodium-potassium pump actively transports sodium ions out of the cell and potassium ions into the cell, contributing to the maintenance of these concentration gradients.

When a cell is stimulated, such as by a neurotransmitter or an electrical signal, the permeability of the membrane to certain ions can change. This leads to a rapid influx or efflux of ions, causing a transient change in the membrane potential. These changes are crucial for various cellular functions, including nerve impulse transmission, muscle contraction, and hormone secretion. If the membrane potential reaches a certain threshold, an action potential can be generated, which is a rapid, all-or-none electrical signal. The precise value and dynamics of membrane potential are tightly regulated and essential for cellular life.