hodgkin-huxley-sim is a free neuron-dynamics learning tool implementing Hodgkin & Huxley 1952 J Physiol's four coupled ODEs (C·dV/dt = −gNa·m³h·(V−ENa) − gK·n⁴·(V−EK) − gL·(V−EL) + I + gating dm/dh/dn/dt = α(1−x) − β·x) + Goldman-Hodgkin-Katz auto-computed ENa/EK/EL + RK4 Δt=0.01 ms time step + absolute/relative refractory periods, all visualised with in-house RK4 solver and oscilloscope SVG (Kandel Ch.7 / Hille Ion Channels baseline, zero npm).

(1) Static action potential figures → RK4 4-order coupled ODE dynamic simulation (2) Learn gating variables m/h/n traces (Na⁺ activation/inactivation + K⁺ activation) (3) Goldman-Hodgkin-Katz equilibrium potential auto baseline (undergrad neuroscience) (4) 5 scenarios (subthreshold / threshold / suprathreshold / refractory / extracellular K⁺ change) (5) Bonus RK4 numerical methods learning (Δt=0.01 ms precision) (6) Zero external libs

① Stimulus current I slider (0-30 μA/cm²) + pulse duration (0.1-10 ms) ② Sandbox: click-to-stimulate electrode pulse (intensity/duration) ③ RK4 Δt=0.01 ms auto-evolves → membrane V(t) oscilloscope SVG live ④ Gating m/h/n auxiliary traces shown simultaneously ⑤ ENa/EK/EL Goldman-Hodgkin-Katz auto-displayed ⑥ 5 quick scenarios: • Subthreshold (I=10 μA/cm²) → no AP • Threshold (I=15 μA/cm²) → single AP • Suprathreshold (I=20 μA/cm²) → train • Refractory (1st pulse + 1 ms later 2nd) → 2nd AP fails (absolute refractory) • Extracellular K⁺ change → resting potential shift ⑦ Hover 18 academic terms (action potential / membrane potential / voltage-gated / gating / threshold / refractory / Nernst / Goldman-Hodgkin-Katz / RK4 / Na/K pump, etc.)

Example 1) I=0 → V resting ≈ −65 mV (RK4 stable equilibrium) Example 2) I=10 μA/cm² (subthreshold) → no AP Example 3) I=15 μA/cm² (threshold) → 1 AP (depolarisation → repolarisation → hyperpolarisation) Example 4) I=20 μA/cm² (suprathreshold) → train Example 5) 1st pulse + 1 ms later 2nd pulse (absolute refractory) → 2nd AP fails