[Ultrastructural characteristics of nodes of Ranvier]

Three types of the Ranvier nodes (conductive, presynaptic and receptor-like) were distinguished on the basis of investigations of the ultrastructure of peripheral and central nerve fibres of the frog and cat. Presynaptic nodes are characterized by the presence of large asymmetrical prominences, synaptic vesicles and membrane specialization. Receptor-like nodes have symmetrical prominences filled with mitochondria, nude neurolemma similar to that of receptor plates. In all types of nodes microtubules usually do not enter the protrusions of the neuroplasm.