Hiperpolarizáció

Hiperpolarizáció refers to a state where a biological membrane, typically the plasma membrane of a cell, becomes more polarized than its resting potential. The resting potential itself is a difference in electrical charge across the membrane, with the inside of the cell usually being more negative than the outside. When a cell undergoes hyperpolarization, the membrane potential becomes even more negative, moving further away from zero.

This phenomenon is often caused by the influx of negative ions into the cell or the efflux of positive ions out of the cell. Specific ion channels, such as potassium channels or chloride channels, play a crucial role in mediating these ion movements. For example, if potassium channels open and allow potassium ions to flow out of the cell, the inside becomes more negative, leading to hyperpolarization. Similarly, the influx of chloride ions can also cause hyperpolarization.

Hyperpolarization is a critical process in cellular signaling, particularly in excitable cells like neurons and muscle cells. It generally makes it more difficult for a cell to reach its threshold potential for firing an action potential. This inhibitory effect can be used to regulate neuronal activity, preventing excessive firing or dampening signals. In neurons, hyperpolarization can occur after an action potential, during the refractory period, and also in response to inhibitory neurotransmitters. The duration and extent of hyperpolarization can vary depending on the cell type and the specific stimulus.