The Hodgkin-Huxley model explains how neurons fire action potentials. Scientists Alan Hodgkin and Andrew Huxley developed it in 1952. They studied the giant axon of a squid. Their work earned a Nobel Prize later.
Neurons maintain a resting membrane potential first. This potential stays around -70 mV inside the cell. Sodium ions stay outside. Potassium ions stay mostly inside. Ion channels control this balance.
When a stimulus arrives, the membrane depolarizes slightly. Voltage-gated sodium channels open quickly. Sodium ions rush into the cell. The inside becomes more positive. This creates a rapid rise in voltage.
Next, sodium channels inactivate fast. At the same time, voltage-gated potassium channels open slowly. Potassium ions flow out of the cell. The membrane repolarizes. The voltage drops back toward rest.
Moreover, potassium channels stay open a bit longer. This causes a brief hyperpolarization. The membrane becomes more negative than rest. This phase helps prevent immediate re-firing.
The model uses four key equations. One describes the membrane potential change. Three others track gating variables. These variables represent sodium activation (m), sodium inactivation (h), and potassium activation (n).
Each gating particle moves between open and closed states. The rates depend on voltage. Hodgkin and Huxley measured these rates carefully. Their math captures the real behavior of ion channels.
Furthermore, the model predicts action potential shape accurately. It shows the all-or-nothing response. Small stimuli fail to trigger spikes. Stronger ones produce full action potentials.
Researchers still use this model today. It forms the basis for many neuron simulations. Modern versions add more channel types. Yet the original equations remain powerful and elegant.
Overall, the Hodgkin-Huxley model changed neuroscience forever. It turned electrical recordings into clear mathematical rules. Scientists now understand nerve impulses much better. This breakthrough continues to inspire new discoveries.