Restpolarisering

Restpolarisering refers to the phenomenon where, after an electric potential difference has been applied across a biological membrane, the membrane potential returns to its resting state. This process is crucial for the functioning of excitable cells, such as neurons and muscle cells. When a cell membrane is stimulated, it undergoes depolarization, meaning its electrical potential becomes less negative or even positive. This change in potential is often caused by the rapid influx of ions like sodium (Na+) across the membrane.

Following depolarization, repolarization is the process that restores the membrane's negative electrical charge. This is typically achieved through the outward movement of positively charged ions, primarily potassium (K+), which flow out of the cell down their electrochemical gradient. Voltage-gated potassium channels play a key role in this phase, opening in response to the depolarization and allowing K+ to exit. This efflux of positive charge makes the inside of the cell more negative again.

Sometimes, repolarization can overshoot, leading to hyperpolarization, where the membrane potential becomes even more negative than the resting potential. This is then followed by a slow return to the resting potential through the action of ion pumps and leak channels. The precise timing and magnitude of restpolarisering are critical for processes like nerve impulse transmission and muscle contraction, ensuring that cells can respond to subsequent stimuli effectively.