Among somatic nerve fibers, which statement is true about preganglionic and postganglionic conduction velocities?

• A. Postganglionic fibers are faster because they are larger
• B. Preganglionic fibers are faster because they are myelinated and larger
• C. Both have the same velocity
• D. Postganglionic fibers are faster because they are unmyelinated

Answer: (B)

Conduction velocity is mainly determined by myelination and fiber diameter. Myelinated fibers conduct impulses quickly through saltatory conduction, and larger-diameter fibers have lower internal resistance, enabling faster transmission. Preganglionic fibers are myelinated and generally larger than postganglionic fibers, which are unmyelinated and smaller. This combination makes preganglionic fibers conduct impulses faster than postganglionic fibers. The other statements don’t fit because postganglionic fibers are not faster due to being unmyelinated or smaller, and they don’t share the same velocity as preganglionic fibers.