nerve /nurv/ [L, nervus] , one or more bundles of impulse-carrying fibers, myelinated or unmyelinated or both, that connect the brain and the spinal cord with other parts of the body. Nerves transmit afferent impulses from receptor organs toward the brain and spinal cord and efferent impulses peripherally to the effector organs. Each nerve consists of an epineurium enclosing fasciculi of nerve fibers; each fasciculus is surrounded by its own sheath of connective tissue, or epineurium. Individual nerve fibers, which are microscopic, consist of formed elements within a matrix of protoplasm enclosed in endoneurium that are enclosed in a neurilemmal sheath. Inside the neurilemma are nerve fibers, also enclosed in a myelin sheath. See also axon, dendrite, neuroglia, neuron, Schwann cell.
