Which nerve fiber conducts action potentials the most rapidly?

Which nerve fiber conducts action potentials the most rapidly?

• A. A-delta fiber
• B. A fiber
• C. C fiber
• D. B fiber

Answer: (B)

Conduction velocity depends mainly on myelination and axon diameter. Heavily myelinated, large-diameter fibers enable rapid saltatory conduction, so they transmit signals fastest. Among the options, the A fiber has the largest diameter and is well myelinated, giving the highest conduction speed. A-delta fibers are smaller and only moderately fast, B fibers are myelinated but smaller than A fibers, and C fibers are unmyelinated and slowest. Thus, the fastest conduction occurs in the A fiber.

Conduction velocity depends mainly on myelination and axon diameter. Heavily myelinated, large-diameter fibers enable rapid saltatory conduction, so they transmit signals fastest. Among the options, the A fiber has the largest diameter and is well myelinated, giving the highest conduction speed. A-delta fibers are smaller and only moderately fast, B fibers are myelinated but smaller than A fibers, and C fibers are unmyelinated and slowest. Thus, the fastest conduction occurs in the A fiber.