Jänniteriippuvaisuus

Jänniteriippuvaisuus, known in English as voltage dependence or voltage gating, is a property of certain biological molecules, particularly ion channels, that influences their behavior based on the electrical potential difference across a membrane. This phenomenon is crucial for the transmission of electrical signals in excitable cells like neurons and muscle cells.

When the voltage across a cell membrane changes, it can induce a conformational change in voltage-dependent proteins. In the case of ion channels, this change can cause the channel to open or close, thereby altering the flow of ions across the membrane. Different voltage-gated ion channels respond to specific voltage ranges. For example, voltage-gated sodium channels are typically closed at resting membrane potential but open rapidly when the membrane depolarizes, allowing sodium ions to rush into the cell. Conversely, voltage-gated potassium channels often open more slowly during depolarization, facilitating potassium efflux and contributing to repolarization.

This mechanism underlies the generation and propagation of action potentials, the electrical impulses that enable communication in the nervous system and muscle contraction. The precise voltage dependence of these channels allows for the fine-tuning of cellular excitability and responsiveness to stimuli. Beyond ion channels, other proteins, such as certain voltage-sensitive dyes and some neurotransmitter transporters, also exhibit voltage dependence.