Definition

1. Noun:
   • A rapid, temporary change in the electrical potential across a cell membrane: An "action potential" is a fundamental electrical signal in excitable cells like neurons and muscle cells. It is a brief, self-propagating reversal of the membrane potential that travels along the cell.
   • The mechanism for transmitting nerve impulses: It is the primary means by which information is communicated within the nervous system and to muscles.

Usage Examples

• Noun:
  • The neuron fired an action potential. (The neuron generated and propagated this specific electrical signal.)
  • The propagation of the action potential along the axon is very fast. (The travel of this electrical signal along the nerve fiber is rapid.)
  • Researchers measured the action potential in the muscle cell. (Scientists recorded the characteristic voltage change in the muscle cell.)

Advanced Usage

• "To generate/initiate an action potential": To trigger the start of this electrical event, typically when a stimulus depolarizes the membrane to a threshold voltage.
  • Sodium ions rushing into the cell help generate the action potential.
• "The refractory period following an action potential": The brief period after an action potential during which the cell cannot immediately fire another one.
  • During the refractory period, the neuron cannot generate a new action potential.

Variants and Related Words

• Depolarization (n): The phase of the action potential where the membrane potential becomes less negative, moving toward a positive value.
• Repolarization (n): The phase where the membrane potential returns to its negative resting value after depolarization.
• Hyperpolarization (n): A temporary state where the membrane potential becomes more negative than the resting potential.
• Threshold potential (n): The critical level of depolarization required to initiate an action potential.

Synonyms

• Nerve impulse: Often used interchangeably, though "nerve impulse" can refer more broadly to the signal, of which the action potential is the electrochemical component.
• Spike (informal in neuroscience): A colloquial term for the sharp peak of an action potential on a graph.

Related Phrases

• "All-or-none" principle: A key property of the action potential stating that it either occurs fully if the threshold is reached, or does not occur at all.
  • The action potential follows an all-or-none principle; there is no partial signal.
• "Propagate an action potential": To describe the action potential traveling along the membrane.
  • The myelinated sheath allows the axon to propagate the action potential more efficiently.

Noun

1. the local voltage change across the cell wall as a nerve impulse is transmitted