C fibers are sensory fibers in the body, which means that they transmit sensory information. C fibers are specifically known to transmit slow burning pain, warmth, sensual touch, itching, and burning/cramping from muscle exercise. They respond to stimuli with strong intensity and are responsible for slow, dull, chronic, pain. C fibers are present in peripheral nerves (nerves outside of the brain and spine). C fibers are known as afferent nerves, which means that the send information to the central nervous system (brain and spine). C fibers stimulate pain receptors (known as nociceptors), which helps communicate initial information about pain to the body.
C fibers are unmyelinated, which means they lack myelin, a fatty substance that covers nerves which helps them transmit messages fast. Thus, c fibers are slow due to the lack of myelin. Specifically, c fibers conduct impulses slowly (known as slow conduction velocity) at a speed of no more than two meters per second. A meter is approximately 39 inches (slightly more than 3 feet). C fibers are 0.2 to 1.5 micrometers (one millionth of a meter) in diameter, which means they are really, really, really small. Compare c fibers to a delta fibers, which are myelinated and thus transmit sensory information fast, which is perceived as acute sharp pain.