The three main factors that determine how quickly an action potential will travel are: 

1. Myelin sheath: The presence of a myelin sheath increases the speed at which action potential travels. This is because the myelin sheath acts as an insulator, preventing current from leaving the axon. Instead, the action potential skips along the axon in a process known as saltatory conduction. In fibers that are unmyelinated, every part of the axonal membrane has to undergo depolarization, which slows down the speed of action potential consideration. 
2. AxonDiameter: Axons with larger diameters allow for faster action potential travel as there is less leakage of ions in wider axons.
3. Temperature - The higher the temperature the faster the action potential travels. This is because higher temperatures increase the efficiency of enzymes that control the sodium-potassium pump needed to produce action potentials.