Final answer:
The diameter of a nerve fiber significantly influences conduction velocity by affecting the resistance to ion flow, with larger diameters facilitating faster propagation of action potentials.
Step-by-step explanation:
The diameter of a nerve fiber is indeed a key determinant of conduction velocity. A larger diameter reduces the internal resistance to the flow of ions, such as Na+, that propagate the electrical signal, similar to the way greater vessel diameter reduces resistance to blood flow. So, the larger the diameter of the axon, the faster the propagation of the action potential. In unmyelinated axons, this principle is depicted through continuous conduction. In contrast, saltatory conduction occurs in myelinated axons and enables even quicker signal transmission, as the action potential 'jumps' from node to node. This can be compared to electrical conduction, where the density of charge carriers affects the current flow in conductors with identical cross-sections.