When a neuron reaches a threshold of about −55 mV, it fires an all-or-nothing spike. First sodium floods in. Then potassium floods out. Hit Stimulate and follow the voltage.
Action potential
Resting−70 mV
💡 It is all-or-none. Below threshold, nothing happens. At threshold, you get the same full-size spike every time. A stronger stimulus makes spikes fire more often, not bigger.
📷 Reference image
A real labeled figure to compare with the interactive above.
The Action Potential — OpenStax, CC BY 4.0 (via Wikimedia Commons)
