Study of conduction in a new model of the myelinated nerve fiber

A new mathematical model of the myelinated nerve fiber was applied to the study of conduction behavior. This model represents the myelinated nerve fiber as a multiaxial equivalent electric circuit incorporating separate intra-axonal, periaxonal and extra-axonal longitudinal conductive pathways with independent representations of the myelin sheath versus the underlying axolemmal membrane. A detailed anatomical representation of the node is included, with the periaxonal space extending to the nodal compartment. Both amphibian and mammalian nerve fibers were modeled. Model results show a physiological conduction velocity of 57.6 m/s for 17.5-μm-diameter mammalian nerve fiber at 37°C with a change in conduction velocity versus temperature closely correlated to experimental findings. The periaxonal space width and the axon radius in the paranodal region are shown to have a strong influence on conduction velocity