The mechanism of propagation of nerve impulse in a myelinated nerve fibre is different from that of an unmyelinated fibre of the same diameter. Salutatory means 'leaping'. The impulse actually travels by leaping through the nodes of Ranvier in a myelinated fibre. Thus, the local circuits occur only at the nodes. At each node, the action potential is boosted to the same height by ionic mechanisms.
In the rest of the inter-modes, such an exchange of ions is not possible due the presence of myelin sheath. This lipoidal layer of myelin acts as an insulator. It has been found that a nerve impulse can jump across one node, but not two of them. In this case, the third node is beyond the operation of the electric field. The motor neurons, which have to work very swiftly, are all myelinated, and have high speed of transmission of the nerve impulse.
In the rest of the inter-modes, such an exchange of ions is not possible due the presence of myelin sheath. This lipoidal layer of myelin acts as an insulator. It has been found that a nerve impulse can jump across one node, but not two of them. In this case, the third node is beyond the operation of the electric field. The motor neurons, which have to work very swiftly, are all myelinated, and have high speed of transmission of the nerve impulse.