Peripheral nerve

A longitudinal section of a nerve fascicle, shows several myelinated axons.  Two nodes of Ranvier are  visible between adjacent internodes of the myelin sheath.  The axon can be seen passing through the nodal region; Schwann cell nuclei are visible between vacuolated-appearing myelin sheaths.  1000x

The myelin sheath is composed of a series of segments called internodes.  Each internode consists of multiple, concentric wrappings of the plasma membrane of a single Schwann cell.  The myelin membrane is uniquely high in lipid, which provides insulation for the axon and results in increased conduction velocity of the action potential.

The node of Ranvier is a specialized region of the axonal plasma membrane located in the gap between adjacent myelin internodes.  The node of Ranvier possesses a high concentration of sodium channels, which propagate the action potential.

A longitudinal section of a nerve fascicle, shows several myelinated axons.  Two nodes of Ranvier are  visible between adjacent internodes of the myelin sheath.  The axon can be seen passing through the nodal region; Schwann cell nuclei are visible between vacuolated-appearing myelin sheaths.  1000x