Membranapotentsiaal

Membranapotentsiaal refers to the difference in electrical potential between the interior and exterior of a biological membrane, most notably the plasma membrane of cells. This potential arises from the uneven distribution of ions across the membrane, primarily due to the action of ion pumps and channels.

In a resting cell, the membrane potential is known as the resting membrane potential. This state is typically characterized by a negative charge inside the cell relative to the outside. This negativity is maintained by the sodium-potassium pump, which actively transports sodium ions out of the cell and potassium ions into the cell, creating concentration gradients. Leak channels, particularly those permeable to potassium, allow potassium ions to diffuse out of the cell, further contributing to the negative interior.

When a cell is stimulated, the membrane potential can change dynamically. Depolarization occurs when the interior of the membrane becomes less negative or more positive. This can be triggered by the influx of positive ions, such as sodium. If depolarization reaches a certain threshold, an action potential is generated in excitable cells like neurons and muscle cells. An action potential involves a rapid, transient reversal of the membrane potential, characterized by a large influx of sodium ions followed by an efflux of potassium ions. Repolarization then restores the membrane potential to its resting state.

Membrane potentials are fundamental to cellular function, enabling processes such as nerve impulse transmission, muscle contraction, and nutrient transport. The precise regulation of ion movement across membranes is crucial for maintaining cellular homeostasis and executing these vital physiological activities.