Conduction velocity (m/s) of nerve fibers carrying fast pain is about

(C) # Fast pain, like pricking yourself with a needle or touching a burning object, is mainly related to painful stimuli of the skin, mouth and anus. It is transmitted by relatively thick nerve fibers, although this is relative, because they are still microscopically thin, with a diameter of 2 to 5 thousandth of a millimeter. These nerves are called A-delta fibers. Because of their relatively thick size, these nerve fibers allow the pain stimulus to be transferred very fast (at a speed of five to 30 meter/second), hence the name. This is all to make the body withdraw immediately from the painful and harmful stimulus, in order to avoid further damage.# Slow pain, which starts immediately after the fast pain, is transmitted by very thin nerve fibers, called C-nerve fibers (their diameter is between 0.2 to 1 thousandth of a millimeter). Because of their small size, the pain impulse can only be transmitted slowly to the brain, at a speed of less than 2 meters per second. The response of the body is to hold the affected body part immobile (guarding, spasm or rigidity), so that healing can take place.