Neuropeptides and Classic Innervation: Neural Structures in Human Airways

The earlier concepts of innervation of human airways have been undergoing change owing to expanded research. The autonomic nervous system of the airways is more complex than originally believed. The autonomic nervous system is composed of the sympathetic (adrenergic) and parasympathetic (cholinergic) systems consisting of efferent (motor) and afferent (sensory) pathways. The efferent fibers to the bronchial smooth muscle and submucosal glands arise from ganglia. In the parasympathetic system, airway ganglia receiving preganglionic fibers from the vagal nuclei from the central nervous system (CNS) are mainly located in the airway wall external to the smooth muscle and cartilage. Only a few smaller ganglia are situated in the submucosa. In the sympathetic system in humans, the preganglionic fibers leave the spinal cord and synapse with the prevertebrate ganglia. Postganglionic fibers then enter the lungs. It is generally accepted that virtually all afferent nerve fibers to the CNS from the airways travel in the vagus nerve (Richardson and Ferguson, 1979; Murray, 1986). © 1994 by Marcel Dekker, Inc. All Rights Reserved.