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Home/Biophysics, Fluids & Geoscience/Hodgkin–Huxley Action Potential

Hodgkin–Huxley Action Potential

The Hodgkin–Huxley model describes excitable biological membranes with voltage-dependent sodium and potassium conductances controlled by gating variables (m, h, n). A depolarizing current raises V; once sodium channels open, positive feedback drives the upstroke, after which potassium repolarizes the cell. This page integrates the classical squid-axon parameter set with RK4 and plots membrane voltage together with effective conductances.

Who it's for: Undergraduates in biophysics or neuroscience learning action potentials beyond integrate-and-fire cartoons.

Key terms

  • Hodgkin–Huxley
  • Action potential
  • Sodium channel
  • Potassium channel
  • Gating
  • RK4

RK4 on the HH ODEs; pulse starts at 1 ms. Increase I or pulse width to cross threshold and fire.

Live graphs

Stimulus

12 µA/cm²
2 ms
40 ms

Classical Hodgkin–Huxley (squid giant axon parameters): C dV/dt = I − g_Na m³h(V−E_Na) − g_K n⁴(V−E_K) − g_L(V−E_L), with α/β kinetics for m,h,n. A depolarizing current pulse from t = 1 ms can trigger an action potential if above threshold.

Measured values

Peak V40.5 mV

How it works

Numerical integration of the Hodgkin–Huxley excitable membrane: sodium activation/inactivation and potassium activation produce the stereotyped spike; conductance traces show channel gating.

Frequently asked questions

Why two graphs for voltage and conductances?
V spans tens of millivolts while g_Na m³h and g_K n⁴ peak on a different scale; overlaying them on one autoscaling axis would hide one of the traces.