In the structure of a human neuron, the nodes of Ranvier are found on

The myelinated nerve fibres are enveloped with Schwann cells, which form a myelin sheath around the axon. The gaps between two adjacent myelin sheaths are called nodes of Ranvier. Myelinated nerve fibres are found in spinal and cranialnerves.Unmyelinated nerve fibre is enclosed by a Schwann cell that does not form a myelin sheath around the axon, and is commonly found in autonomous and the somatic neural systems. So, nodes of Ranvier are not found in ANS and SNS containing non medullated nerve fibres.