Explain what causes the conduction of impulses along a non-myelinated axon to be slower than along a myelinated axon.

In myelinated axons, the myelin sheath that surround the membrane prevents action potentials forming, hence depolarisation only occurs at the nodes of Ranvier (breaks in the sheath, exposing the membrane, at intervals of around 2mm). Impulses therefore 'jump' from node to node in a process called saltatory conduction. This is a much faster process than that which occurs along non-myelinated axons, whereby depolarisation occurs along the entire length of the axon.