Why do myelinated axons propagate action potentials faster than unmyelinated axons?

Unlike unmyelinated axons, myelinated axons are surrounded by an insulatory myelin sheath produced by Schwann cells. Because of this insulatory sheath, action potentials cannot occur along the entire length of a myelinated axon but only at the gaps between Schwann cells, known as Nodes of Ranviers. This results in the action potential 'jumping' along the axon in a process known as saltatory conduction, and thus propagating much more quickly than along an unmyelinated axon.