Action potential
Action Potential
Action potential (pronounced: ak-shun po-ten-shul) is a short-term change in the electrical potential on the surface of a cell, especially of a nerve or muscle cell, that leads to the transmission of nerve impulses.
Etymology
The term "action potential" originates from the Latin words "actio" meaning action, and "potentia" meaning power. It was first used in the context of bioelectricity in the 1950s.
Definition
An Action potential is a rapid, temporary change in a cell's membrane potential. It is initiated by a stimulus and is usually carried along the membrane of a neuron or muscle cell. In neurons, action potentials play a central role in cell-to-cell communication. In muscle cells, they are involved in coordinating contraction.
Process
The process of an action potential involves several stages:
- Resting potential: The cell membrane is at rest with a negative charge on the inside and a positive charge on the outside.
- Depolarization: A stimulus causes some sodium channels to open, allowing positively charged sodium ions to enter the cell.
- Repolarization: After the peak of the action potential, potassium channels open, allowing positively charged potassium ions to exit the cell.
- Hyperpolarization: The potassium channels stay open slightly too long, causing an overshoot of the membrane potential.
- Return to resting potential: The sodium-potassium pump restores the resting potential.
Related Terms
- Resting potential: The electrical potential of a neuron or other excitable cell relative to its surroundings when not stimulated or involved in passage of an impulse.
- Depolarization: A change in a cell's membrane potential, making it more positive, or less negative.
- Hyperpolarization: An increase in the cell's membrane potential, making it more negative.
- Sodium-potassium pump: A protein that pumps sodium ions out of the cell and potassium ions into the cell.
External links
- Medical encyclopedia article on Action potential
- Wikipedia's article - Action potential
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