Figure 14-3 Pattern of "local circuit currents" flowing during impulse propagation in a nonmyelinated C fiber's axon (A) and a myelinated axon (B). During propagation of impulses, from left to right, current entering the axon at the initial rising phase of the impulse (gray downpointing arrows) passes through the axoplasm (local circuit current, red loops) and depolarizes the adjacent membrane. Plus and minus signs adjacent to the axon membrane indicate the polarization state of the axon membrane: negative inside at rest, positive inside during active depolarization under the action potential, and less negative in the regions where local circuit currents flow. This ionic current passes relatively uniformly across a nonmyelinated axon, but in a myelinated axon it is restricted to entry at the nodes of Ranvier, several of which are simultaneously depolarized during a single action potential.