the categorization of peripheral nerve fibers in accordance with their diameters, speeds of conduction, and positions. They lie in three primary categories, that can be further separated into subsections, A fibers span from 6 to 20 with regard to their diameter, whereas B fibers take place within the preganglionic autonomic nervous system- they’re myelinated but of fairly minute diameter, and conduct more gradually than A fibers, C fibers span from 0.2 to 1.5 pm with regard to their diameter- they’re not myelinated and conduct gradually.