A myelinated neurone is insulated by a layer of Schwann cells that make up the myelin sheath. This aids in the faster conduction of an action potential down the neuronal axon. Depolarisation of the axon can only occur at regions of the axon that are not myelinated (i.e. are not surrounded by Schwann cells), these regions are called the Nodes of Ranvier. Therefore, in myelinated neurones, the nerve impulse is said to jump from node - to - node, a impulse pathway known as Saltatory Conduction. This means that the action potential does not have to travel along the whole length of the myelinated axon. This translates to an increased speed in the transmission of the nerve impulse across an entire myelinated axon compared to along a non-myelinated axon.