Which type of pain fiber is associated with slow conduction velocity and is unmyelinated?

• A. A-alpha fibers
• B. A-delta fibers
• C. B fibers
• D. C fibers

Answer: (D)

The type of pain fiber associated with slow conduction velocity and being unmyelinated is C fibers. C fibers are a class of nerve fibers that are known for their slow transmission speed, which can range from 0.5 to 2.0 meters per second. This slow conduction is a result of their unmyelinated structure, which lacks the insulating myelin sheath that speeds up impulse conduction in other types of fibers.

C fibers are primarily responsible for transmitting dull, aching, or chronic pain sensations, as well as temperature sensations. Their unmyelinated nature contributes to the slow and diffuse quality of the pain they convey, which stands in contrast to the fast-conducting, myelinated fibers that carry sharp, acute pain sensations.

In this context, understanding the different types of nerve fibers and their characteristics—such as myelination and conduction velocity—is crucial for comprehending the mechanisms of pain transmission and the clinical implications of pain management.