When a depolarizing current is injected into a cell, the resultant decrease in the membrane potential activates the voltage-dependent Na⁺ channels. The activation of the Na⁺ channels in turn accelerates the depolarization process, producing the rising phase of the action potential. The rise of the membrane potential ultimately triggers the process of Na⁺ channel inactivation, which prevents further membrane depolarization. At the same time, the voltage-dependent K⁺ channels are activated, repolarizing the cell and producing the falling phase of the action potential and the afterhyperpolarization.

The default parameters are:

• Maximum value of voltage-dependent Na⁺ conductance: 1500 uS
• Maximum value of voltage-dependent K⁺ conductance: 360 uS
• Na⁺ equilibrium potential: 55 mV
• K⁺ equilibrium potential: -75 mV