hvilespændingen

Hvilespændingen, also known as the "resting membrane potential" in English, is a fundamental concept in physiology and neuroscience. It refers to the electrical potential difference across the plasma membrane of a cell when it is at rest, meaning it is not actively conducting an action potential or any other electrical activity. This potential is typically measured in millivolts (mV) and is crucial for the proper functioning of excitable cells, such as neurons and muscle cells.

The resting membrane potential is primarily determined by the distribution of ions across the cell membrane. The most significant ions involved are sodium (Na+), potassium (K+), and chloride (Cl-). The cell membrane is selectively permeable to these ions, allowing some to pass through while blocking others. This selective permeability creates an electrochemical gradient, which drives the ions to move across the membrane, generating a voltage difference.

In most excitable cells, the resting membrane potential is negative, usually around -70 mV. This negative potential is maintained by the active transport of ions, particularly the sodium-potassium pump, which actively transports three sodium ions out of the cell for every two potassium ions it brings in. This pump helps to maintain the high concentration of potassium ions inside the cell and the low concentration of sodium ions, contributing to the negative resting membrane potential.

The resting membrane potential is essential for the initiation and propagation of action potentials. When a cell is stimulated, the membrane potential can depolarize, leading to the generation of an action potential. The resting membrane potential provides the baseline from which these changes occur, ensuring that the cell can respond appropriately to various stimuli.