Action potentials
Action Potentials
Action potentials (pronounced: ak-shun po-ten-shuls) are short-lasting events in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. These are essential for the propagation of signals along the neuron's axon.
Etymology
The term "action potential" is derived from the Latin words "actio" meaning action, and "potentialis" meaning potential. It was first used in the context of bioelectricity in the 1940s.
Definition
An action potential is a rapid, temporary change in a cell's membrane potential. It typically begins with a rapid depolarization, followed by a repolarization phase, and often a hyperpolarization phase. This process is crucial for the transmission of signals within the nervous system.
Generation
The generation of an action potential is initiated by a significant change in the membrane potential, usually a depolarizing current. This change triggers the opening of voltage-gated ion channels, which allow an influx of sodium ions into the cell. This influx causes a further increase in the membrane potential, leading to the generation of the action potential.
Propagation
The propagation of action potentials along a neuron's axon is a key process in the transmission of signals within the nervous system. This propagation is facilitated by the myelin sheath, a fatty layer that insulates the axon and increases the speed of signal transmission.
Related Terms
- Resting potential: The membrane potential of a cell when it is not being stimulated or inhibited.
- Depolarization: A decrease in the difference in voltage between the inside and outside of a cell.
- Repolarization: The process by which the membrane potential of a cell returns to its resting potential after depolarization.
- Hyperpolarization: An increase in the difference in voltage between the inside and outside of a cell, making it less likely to generate an action potential.
- Voltage-gated ion channels: Protein channels in the cell membrane that open or close in response to changes in the membrane potential.
- Myelin sheath: A fatty layer that insulates the axon of a neuron, increasing the speed of signal transmission.
External links
- Medical encyclopedia article on Action potentials
- Wikipedia's article - Action potentials
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