membránpotenciál

Membránpotenciál refers to the electrical potential difference that exists across the plasma membrane of a cell. This potential difference arises primarily from the uneven distribution of ions, such as sodium (Na+), potassium (K+), chloride (Cl-), and calcium (Ca2+), across the cell membrane. These ions are moved by various ion channels and pumps, which are proteins embedded within the membrane.

The resting membrane potential is the electrical potential difference across the plasma membrane of a non-excited cell. This potential is typically negative inside the cell relative to the outside, often in the range of -60 to -90 millivolts. This negative charge is mainly due to the higher concentration of potassium ions inside the cell and the selective permeability of the membrane to potassium ions, allowing them to leak out. The sodium-potassium pump also plays a crucial role by actively transporting sodium ions out of the cell and potassium ions into the cell, contributing to the ionic gradients.

Changes in membrane potential are fundamental to cell signaling, particularly in excitable cells like neurons and muscle cells. Depolarization occurs when the membrane potential becomes less negative or more positive, often due to the influx of positive ions like sodium. Repolarization is the return of the membrane potential to its resting state. Hyperpolarization is when the membrane potential becomes more negative than the resting potential. These rapid changes in membrane potential, known as action potentials, are responsible for transmitting nerve impulses and triggering muscle contractions. The precise maintenance and modulation of membránpotenciál are vital for normal cellular function.