Action potential, ion channel gating dynamics, and spike generation (Nobel Prize 1963)
V (voltage, mV)
m (Na act.)
h (Na inact.)
n (K act.)
I_Na
I_K
Hodgkin-Huxley (1952) model: CdV/dt = I − g_Na·m³h(V−E_Na) − g_K·n⁴(V−E_K) − g_L(V−E_L)
m,h,n are voltage-dependent gating variables. Below threshold (~6.5 μA): subthreshold oscillation.
Above threshold: periodic spiking (tonic firing). I = 0 + pulse: single action potential at ~50mV.
The model captures how Na⁺ channels open fast (depolarization) and K⁺ channels open slow (repolarization).