Why do nerve impulses travel faster in myelinated neurons?

The myelin sheath is a fatty layer made up of the hugely expanded plasma membrane of schwann cells which surround the axon of neurons. The axon is unprotected where the sheath of one cell meets the next and these points are known as nodes of Ranvier. Voltage gated sodium ion channels are confined to the nodes. The influx of sodium ions at one node creates enough depolarization to reach the threshold of the next. This means that the action potential 'jumps' from one node to the next. The process is known as saltatory conduction and results in much faster propagation of the nerve impulse compared to non-myelinated neurons (where action potentials travel as one slow wave)