Action Potential
A rapid, self-propagating electrical voltage impulse along the membrane of excitable cells (neurons and muscle cells).
Governing formula
v_conduction ∝ √(d) (Unmyelinated), v_conduction ∝ d (Saltatory Myelinated)
SI unit
mV (Amplitude ~100 mV) & m/s (Conduction Speed)
In depth
Triggered when membrane depolarization reaches threshold (~-55 mV). Voltage-gated Na⁺ channels open rapidly causing depolarization (+30 mV), followed by Na⁺ inactivation and voltage-gated K⁺ channel opening for repolarization.
Examples in the real world
Saltatory conduction jumping rapidly between Nodes of Ranvier along myelinated motor neuron axons.