Final answer:
The action potential travels down the axon through voltage-gated ion channels. In unmyelinated axons, the process occurs continuously, while in myelinated axons, it occurs through saltatory conduction. Saltatory conduction is faster and depends on the diameter of the axon.
Step-by-step explanation:
The action potential travels down the axon as voltage-gated ion channels are opened by the spreading depolarization. In unmyelinated axons, this happens in a continuous fashion because there are voltage-gated channels throughout the membrane. In myelinated axons, propagation is described as saltatory because voltage-gated channels are only found at the nodes of Ranvier and the electrical events seem to 'jump' from one node to the next. Saltatory conduction is faster than continuous conduction, meaning that myelinated axons propagate their signals faster. The diameter of the axon also makes a difference as ions diffusing within the cell have less resistance in a wider space.