Fig. 1.

The single-cable model. We simulated a generic axon fiber, consisting of 30 repeating INTER-JUXTA-PARA-NODE-PARA-JUXTA-INTER sections. Nodes contained fixed numbers of sodium channels (5 × 10³, 1.5 × 10⁴, or 2.5 × 10⁴), which have fast Na⁺ membrane dynamics and a linear leak conductance. JUXTA sections contained fast-gated potassium channels. While all sections contained a membrane capacitance in parallel with their respective conductance, nonnodal regions contained two capacitors in series, one representing the myelin capacitance C_myelin, and the other representing the membrane capacitance C_mem. The figure is not to scale. INTER, internode; JUXTA, juxtaparanode; PARA, paranode; and NODE, node itself.