Neuroscience Trainingneuroscience.trainingNeural Signaling · Visual Neuroscience
What Is an Action Potential?
An action potential is a brief, all-or-nothing voltage spike: sodium channels open then inactivate, potassium flows out, and in myelinated axons the spike is renewed at each node. Values shown are typical textbook examples; real neurons vary.
Transcript
Neurons signal with brief electrical spikes. Many last around a millisecond, though spike width differs between cell types.
At rest, the inside of many neurons sits around minus sixty-five to minus seventy millivolts, relative to the outside.
Nudge it past threshold, and voltage-gated sodium channels open. Sodium ions rush in, and the inside swings positive.
Within about a millisecond, the sodium channels inactivate. Potassium channels open, potassium flows out, and the voltage falls, briefly dipping below rest.
Each spike is all or nothing. In myelinated axons, it is renewed only at gaps called nodes, where sodium channels cluster, so it travels much faster.
References
- The Action Potential — Anatomy & Physiology (Betts, Young et al.; OpenStax-derived, CC BY), Utah Education Network — https://uen.pressbooks.pub/anatomyphysiology/chapter/the-action-potential/
- Action Potentials — Foundations of Neuroscience (Casey Henley), Michigan State University Libraries — https://openbooks.lib.msu.edu/neuroscience/chapter/action-potentials/
- Bean BP (2007) The action potential in mammalian central neurons. Nature Reviews Neuroscience 8:451–465 — https://doi.org/10.1038/nrn2148
- Conduction velocity and axon diameter — Monash University Physiology iLearn — https://ilearn.med.monash.edu/physiology/action-potentials/axon-diameter
- The Membrane at Rest — Introduction to Neuroscience (Valerie Hedges), Michigan State University Libraries — https://openbooks.lib.msu.edu/introneuroscience1/chapter/the-membrane-at-rest/
Narration uses a synthetic voice. Animations are simplified illustrations of the mechanisms described. Educational content, not medical advice.
