Fig. 1.

Schematic of axon structure and ion channel distribution, demonstrating the node of Ranvier with high density of voltage-gated Na⁺ channels [both transient (Na_t) and persistent (Na_p)] and slow K⁺ channels (K_s). The internode under the myelin sheath is depicted with fast K⁺ channels (K_f) located adjacent to the node, the hyperpolarization activated cation conductance (I_h), slow K⁺ channels, and voltage-independent leak conductances (Lk) along with the energy dependent Na⁺/K⁺ pump and the Na⁺/Ca²⁺ exchanger