Herbert Spencer Gasser in the context of Nobel Prize for Physiology or Medicine

Group A nerve fibers are one of the three classes of nerve fiber as generally classified by Erlanger and Gasser. The other two classes are the group B nerve fibers, and the group C nerve fibers. Group A are heavily myelinated, group B are moderately myelinated, and group C are unmyelinated.

The other classification is a sensory grouping that uses the terms type Ia and type Ib, type II, type III, and type IV, sensory fibers.

Group B nerve fibers are one of the three classes of nerve fiber as generally classified by Erlanger and Gasser. They are moderately myelinated, which means less myelinated than group A nerve fibers, and more myelinated than group C nerve fibers. They have a medium conduction velocity of 3 to 14 m/s. They are usually general visceral afferent fibers and preganglionic nerve fibers of the autonomic nervous system. They are used in Bainbridge reflex as afferents.

Joseph Erlanger (January 5, 1874 – December 5, 1965) was an American physiologist who is best known for his contributions to the field of neuroscience. Together with Herbert Spencer Gasser, he identified several varieties of nerve fiber and established the relationship between action potential velocity and fiber diameter. They were awarded the Nobel Prize in Physiology or Medicine in 1944 for these achievements.