The most prominent feature of this cross section, magnified many thousands of times, is the black circular structures, surrounding a light gray interior. This interior (one of which is marked M) is the nerve cell process. The dark surround is another cell type, the Schwann cell. The dark material effectively thickens the nerve cell membrane and changes the way signals propagate along the nerve cells. The presence of this myelin sheath speeds the propagation of signals markedly. Not all nerve cells have the myelin. An unmyelinated nerve cell appears in the lower right corner and is marked u.
The myelinated process marked M is about 12 µm in diameter.
Myelin brings about a marked increase in conduction velocity. The Schwann cells forming the myelin sheath are under study in the Development and Regeneration Laboratory.
©D.F. Davey,
Department of Physiology,
University of Sydney
Last updated 10 April 2002