Final answer:
Action potential conduction is slowest in C fibers, which are unmyelinated as opposed to the faster-conducting myelinated A and B fibers.
Step-by-step explanation:
Action potential conduction velocity is slowest in unmyelinated fibers. When comparing different types of nerve fibers, C fibers are typically the slowest.
These are small-diameter, unmyelinated nerves that carry action potentials at a much lower speed compared to A fibers, which are larger and myelinated, and B fibers, which are also myelinated though smaller than A fibers.
Conduction velocity varies among different fibers due to factors such as diameter and the presence or absence of myelin insulation.
Myelinated fibers tend to conduct action potentials more rapidly through a process known as saltatory conduction. In contrast, unmyelinated fibers utilize continuous conduction, which is slower because the action potential must propagate along every segment of the axon membrane.