Zellmembranpotenzial

Zellmembranpotenzial refers to the electrical potential difference across the plasma membrane of a cell. This potential difference arises from the uneven distribution of ions, primarily sodium (Na+), potassium (K+), calcium (Ca2+), and chloride (Cl-), across the cell membrane. The cell membrane is selectively permeable, meaning it allows certain ions to pass through more easily than others, largely due to the presence of ion channels and pumps.

The resting membrane potential is the stable electrical potential difference that exists across the plasma membrane of a non-excited cell. It is typically negative on the inside relative to the outside. This negative resting potential is primarily established by the outward movement of potassium ions, which are more concentrated inside the cell, and the action of the sodium-potassium pump, which actively transports sodium ions out of the cell and potassium ions into the cell, further contributing to the ionic gradient.

Changes in the membrane potential are crucial for cellular function, particularly in excitable cells like neurons and muscle cells. Depolarization occurs when the membrane potential becomes less negative, often due to the influx of positive ions like sodium. Repolarization is the process of returning the membrane potential to its resting state, usually by the efflux of positive ions like potassium. Hyperpolarization is a change in the membrane potential that makes it more negative than the resting potential. These dynamic changes in membrane potential underlie processes such as nerve impulse transmission and muscle contraction.