Summary
A rapid, all-or-none reversal of membrane potential that travels along an axon.
In depth
When depolarisation reaches threshold (about -55 mV), voltage-gated Na+ channels open, producing a spike to about +30 mV; then Na+ channels inactivate and K+ channels open, repolarising, with brief hyperpolarisation. All-or-none, amplitude fixed; intensity is coded by frequency.
Threshold is the point at which sodium channel opening becomes self-reinforcing. Conduction is non-decremental. Frequency codes intensity.
Common mistake: action potentials do not get larger with a stronger stimulus.
Frequently asked questions
What is Action Potential?
A rapid, all-or-none reversal of membrane potential that travels along an axon.
Which area of biology covers Action Potential, and how advanced is it?
Action Potential is one of the 54 topics in Neuroscience. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Depolarisation and Repolarisation, Voltage-Gated Ion Channels, Hodgkin-Huxley Model.
Can you give an example of Action Potential?
Local anaesthetics such as lidocaine block Na+ channels.
What should I learn before Action Potential?
Work through the Beginner topics in Neuroscience first, such as Nervous System, Neuron, Central and Peripheral Nervous Systems, then return to Action Potential. Intermediate topics assume the Beginner vocabulary.
What topics are related to Action Potential?
The closest topics to Action Potential are Depolarisation and Repolarisation, Voltage-Gated Ion Channels, Hodgkin-Huxley Model, Synaptic Transmission. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Action Potential?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Action Potential. To practise the whole of Neuroscience, use the Neuroscience quiz.
How is Action Potential different from Depolarisation and Repolarisation?
Action Potential: A rapid, all-or-none reversal of membrane potential that travels along an axon. Depolarisation and Repolarisation: Sodium channels open and the cell becomes positive, then potassium channels open to restore the negative interior. Read both side by side and note what each one explains.
What is a common mistake about Action Potential?
Action potentials do not get larger with a stronger stimulus.
How should I study Action Potential step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Depolarisation and Repolarisation and explain the difference aloud. Finally, take the Neuroscience quiz and come back to this page for any question you miss.