A delta fiber

A delta fibers, or Aδ fibers, are a type of sensory fiber. They are associated with cold and pressure, and as nociceptors they convey fast pain information.

They are much faster than the C fibers because they are myelinated, but they are much thinner than other "A" caliber nerve fibers, so they conduct signals more slowly than the other fibers of that class.

The fibers terminate at Rexed lamina I.

Structure

They are thin, myelinated axons with a moderate conduction velocity, or speed of travel of a nerve signal (2 to 30 m/s). These nerve fibers are associated with acute (sharp) pain and therefore constitute the afferent portion of the reflex arc that results in "pulling away" from noxious stimuli (ie: yanking hand away from hot stove). A certain proportion of Aδ fibers are also associated with sensations of temperature (also known as 'cold receptors' in mammals) and pressure. Slowly-conducting, unmyelinated C fibers, by contrast, carry slow, burning pain.

Like other sensory fibers, the Aδ fiber is an extension of a pseudounipolar neuron with its cell body located in a dorsal root ganglion or trigeminal ganglion. Within the spinal cord, afferent nociceptor fibers synapse at or near the spinal cord level where they enter.

See also

• Free nerve ending
• Thermoreceptor

External links

• http://instruct1.cit.cornell.edu/courses/psych396/student2006/the_biology_of_pain_mac_version/functions.html