Excitabilitását

Excitabilitását (excitability) refers to the property of a cell or tissue to respond to a stimulus with a detectable electrical or chemical signal. In biology, excitability is most evident in nerve and muscle cells, where it underpins nerve transmission and muscle contraction. It arises from the cell membrane’s capacity to regulate ion flow through channels, pumps, and exchangers that maintain ionic gradients for ions such as sodium, potassium, calcium, and chloride.

The core mechanism involves changes in the membrane potential. A stimulus that depolarizes the membrane toward a threshold can trigger an action potential, a rapid and all-or-none electrical event that propagates along the cell or along a nerve fiber. The action potential is followed by a refractory period during which the cell is less excitable, helping to regulate the timing and direction of signaling.

Excitability is influenced by several factors, including ion concentration, temperature, pH, and pharmacological agents that modify channel function. It is measured through electrophysiological techniques such as patch-clamp recording, intracellular and extracellular recordings, and voltage-clamp experiments, which reveal properties like resting potential, threshold, and conduction velocity.

Clinical relevance lies in conditions where excitability is altered. Hyperexcitability can contribute to seizures and chronic pain, while hypoexcitability underlies some neuropathies and muscular disorders. Although most prominent in animal nervous and muscular systems, plant and microbial cells can also exhibit forms of excitability, though via different mechanisms and signaling molecules.

In summary, excitabilitását describes the capacity of cells to translate stimuli into electrical or chemical signals, enabling rapid communication and coordinated responses throughout the organism.