Excitable media: action potential propagation on a 1D neural cable
HH equations describe nerve impulse propagation via ion channels:
C dV/dt = I - gNa·m³·h·(V-ENa) - gK·n⁴·(V-EK) - gL·(V-EL) + D·∇²V
Gating variables: m (Na activation), h (Na inactivation), n (K activation) — each follows dm/dt = αm(1−m) − βm·m
Color map: Blue = resting (−65mV), Cyan→White = depolarizing, Red = peak (+40mV), Purple = refractory
Spatial coupling D creates traveling action potentials. Refractory period prevents backfiring.