A Threshold Equation for Action Potential Initiation
Influence of Na inactivation and ionic conductances on spike threshold in the conductance-based model (ka = 3.4 mV, see Materials and Methods).
A, Spike threshold θ as a function of Na+ inactivation variable h, with all other ionic conductances suppressed. B, Threshold as a function of K+ activation variable n, without inactivation (h = 1). C, Threshold as a function of total synaptic conductance (excitatory ge and inhibitory gi), relative to the resting conductance gL (conductances are considered static).