The Length and Diameter of the Node of Ranvier

The physiological significance of the node of Ranvier is now well known. The histological delineation of its length, however, still remains uncertain. Should it be identified as the gap between the myelin sheaths, or the whole part of the narrowed axon? The present analysis, which makes use of the transmission-line theory, shows that both the length and the diameter of the node are definitely related to the fiber diameter, even though these relations are not linear ones. Theoretical curves are constructed, which are expected to fit with the histological measurements pertaining to the effective structure of the node.