ACTIVE EQUIVALENT

CIRCUIT OF THE AXON MEMBRANE

This program shows the equivalent circuit of the membrane capacitance and the three main conductances of the squid giant axon. The conductances are shown as variable resistor, the reversal potentials as batteries and the currents as the degree of darkness in the conductors.

• Interactive Circuit - In this mode, the values of the conductances may be changed manually by dragging the cursor of the variable resistors with the mouse. The leakage conductance can only be turned On or Off by dragging the mouse over the resistor.
• Passive Membrane - In this mode, the conductance values are fixed to the values last used in the Interactive circuit mode and the time course of the currents and membrane voltage are shown in the main screen and in the plot window.
• Simple RC - In this mode, the circuit is simplified to a simple resistor (value of gNa last modified in the Interactive circuit mode) and no battery.
• Membrane Action Potential - In this mode the full solution of the Hodgkin and Huxley equations are shown as a function of time.
• Pulses - This button allows the modification of the current pulses.