Depolarisoitumiseen

Depolarisation is a fundamental process in biology and biochemistry, particularly in the context of nerve cells and muscle cells. It refers to the reversal of the resting membrane potential, which is the difference in electrical charge across the cell membrane. This resting potential is maintained by the selective permeability of the cell membrane to ions, primarily sodium (Na+) and potassium (K+).

When a nerve or muscle cell is at rest, the inside of the cell is negatively charged relative to the outside due to the higher concentration of potassium ions inside the cell. This is maintained by the sodium-potassium pump, which actively transports sodium ions out of the cell and potassium ions into the cell.

Depolarisation occurs when the cell membrane becomes more permeable to sodium ions, allowing them to rush into the cell. This influx of sodium ions causes the inside of the cell to become less negative, or even positive, relative to the outside. This change in membrane potential is what allows the signal to propagate along the nerve or muscle cell.

Depolarisation is a critical step in the generation and transmission of nerve impulses. It is followed by repolarisation, where the membrane potential returns to its resting state, and then hyperpolarisation, where the membrane potential becomes more negative than the resting potential. These processes are essential for the proper functioning of the nervous and muscular systems.