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Neuron Action Potential Simulator

Explore the dynamics of neuronal firing with adjustable parameters. Visualize ion movement, membrane potential changes, and action potential phases.

Simulation Controls

Parameters
Ion Channels

Stimulation

Membrane Properties

Simulation Speed

Understanding Action Potentials

Action potentials are the electrical signals that neurons use to transmit information. They are brief, rapid changes in the electrical potential across the cell membrane, caused by the flow of ions through specialized channels.

The Action Potential Phases

Resting State: The neuron membrane is polarized, with a negative charge inside (-70 mV) relative to outside.

Depolarization: When stimulated above threshold, sodium channels open, allowing Na+ ions to rush in, making the inside of the cell more positive.

Repolarization: Potassium channels open and sodium channels inactivate, allowing K+ ions to flow out, restoring negative charge inside.

Hyperpolarization: Potassium channels remain open briefly, causing the membrane potential to become even more negative than the resting potential.

Recovery: All ion channels return to their resting states, and ion pumps restore the original ion concentrations.

The Hodgkin-Huxley Model

This simulation uses the Hodgkin-Huxley model, a mathematical model that describes how action potentials are initiated and propagated in neurons. The model represents the electrical characteristics of excitable membranes as electrical circuits with resistors and capacitors.

The key equation is:

C_m dV/dt = -g_Na(V-E_Na) - g_K(V-E_K) - g_L(V-E_L) + I_ext

Where:

  • C_m is the membrane capacitance
  • V is the membrane potential
  • g_Na, g_K, and g_L are the conductances of sodium, potassium, and leak channels
  • E_Na, E_K, and E_L are the reversal potentials
  • I_ext is the external current stimulus

Clinical Relevance

Understanding action potentials is crucial for neuroscience and medicine. Many neurological disorders and medications affect ion channels and action potential generation:

  • Local anesthetics block sodium channels, preventing action potentials
  • Epilepsy involves abnormal, excessive action potentials
  • Multiple sclerosis affects myelin, which impacts action potential propagation
  • Cardiac arrhythmias often involve disruptions in action potential timing

Experiment with the simulator to see how changes in membrane properties and ion channel characteristics affect action potential generation and propagation.