What is saltatory conduction?

Motor neurones have a myelin sheath made of Shwann cells. It's an electrical insulator meaning action potentials cannot pass through them. Along the axon there are gaps where there's no myelin sheath, called the 'Nodes of Ranvier'. Depolarisation of a neurone only occurs at these nodes and the cytoplasm of the neurone conducts enough of an action potential for the depolarisation to 'jump' along the nodes of the axon. This is called 'saltatory condution' and means that the impulse travels along the axon a lot faster on a myelinated neurone than a non-myelinated one as the imuplse doesn't have to travel along the whole length of the axon.