The influence of nodal constriction on conduction velocity in myelinated nerve fibers.
Myelinated nerve fibers exhibit a complex anatomy in the nodal region which includes a marked nodal-paranodal constriction and an intricate paranodal structure where the myelin sheath is separated from the axon by a narrow periaxonal space. In this study, a recently developed computational model of the mammalian myelinated nerve fiber based on electron microscopic data was employed to examine the effect of the nodal-paranodal axonal radius and periaxonal space width on the conduction of action potentials. These findings indicate that the nodal-paranodal constriction promotes higher conduction velocities by minimizing the component of the nodal capacity contributed by the paranodal axolemma. Model prediction of optimal nodal-paranodal radii is correlated with radii determined in experimental anatomical studies.
Division of Restorative Neurology and Human Neurobiology, Baylor College of Medicine, Houston, Texas 77030.
J A
JA
Halter
J W
JW
Clark
D000200:Action Potentials / Q000502:physiology; D001369:Axons / Q000502:physiology / Q000648:ultrastructure; D003198:Computer Simulation; D008959:Models, Neurological; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology; D011901:Ranvier's Nodes / Q000502:physiology*; D015222:Sodium Channels / Q000502:physiology
D015221:Potassium Channels; D015222:Sodium Channels