How is an action potential propagated along an axon?

The velocity of nerve impulse conduction is greatest in

a. Heavily myelinated, large-diameter fibers

b. Myelinated, small-diameter fibers

c. Nonmyelinated, small-diameter fibers

d. Nonmyelinated, large-diameter fibers

During a neurobiology lecture, a professor repeatedly refers to group A and group B fibers, absolute refractory period, and myelin sheath gaps. Define these terms.

What are the structural and functional differences among type A, B, and C fibers?

In multiple sclerosis, there is intermittent and progressive damage to the myelin sheath of peripheral nerves. This results in poor motor control of the affected area. Why does destruction of the myelin sheath affect motor control?