Airway Surface Liquid and Respiratory Mucus - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 757

Table 12.1. Sensory and preganglionic and postganglionic sympathetic and parasympathetic
nerves and peptidergic innervation of the respiratory tract (Source: [ 1544 ]; CGRP: calcitonin gene-
related peptide; NAd: noradrenaline; NPY: neuropeptide-Y; VIP: vasoactive intestinal peptide).
Sensory nerves, which have cell bodies mainly in the vagal ganglia, especially the inferior
ganglion of vagus nerve (or nodose ganglion), project axons into the pulmonary blood vessels,
bronchi, cartilage, and other structures. The parasympathetic preganglionic neurons (vagus nerve)
originate from the brain stem (primarily the dorsal motor nucleus and nucleus ambiguus); the
parasympathetic postganglionic neurons innervate the intrapulmonary ganglia in the vascular
adventitia and airway submucosa. Neurons of airway ganglia produce acetylcholine (ACh), VIP,
substance-P (SP), galanin, enkephalins, and nitric oxide (NO). Preganglionic sympathetic fibers
of the lungs originate from the intermediolateral horn of spinal cord segments (T1-T5 column),
postganglionic neurons from ganglia of the sympathetic chain (superior and stellate ganglia). VIP +

and NPY + neurons of sympathetic chain ganglia project to airways.

Released messengers

Nerve type Targets

Parasympathetic nerves (vagus nerve)

Sensory nerves CGRP, SP

Preganglionic nerves ACh

Postganglionic nerves ACh, NO, SP, VIP

Respiratory epithelium, airway smooth muscle,
glands, bronchial arteries

Sympathetic nerves

Preganglionic nerves ACh

Postganglionic nerves NAd, NPY, VIP

Respiratory epithelium, airway smooth muscle,
glands, bronchial arteries

Postganglionic parasympathetic efferent nerves cause bronchoconstriction,
vasodilation; and bronchial gland secretion. Parasympathetic afferent nerves are
sensory fibers of the respiratory epithelium (stretch sensor) that ascend via the
vagus nerves. Stretch receptors lodge in smooth muscles of bronchial walls, most
being slowly adapting (firing with sustained stimulation), but others are rapidly
adapting (transiently firing). Juxtapulmonary (J) receptors localize to alveolar and
bronchial walls are connected to unmyelinated (C-fiber) or myelinated afferent
nerves of vagus nerves. Postganglionic, adrenergic, sympathetic efferent nerves are
bronchodilators, vasoconstrictors, and inhibitors of the glandular secretion.
The parasympathetic nervous system uses not only acetylcholine as a neurotrans-
mitter, but also peptides. Stimulated preganglionic nerves (cell bodies in the medulla
oblongata and nucleus ambiguus) release acetylcholine in the ganglion that targets
nicotinic receptors of postganglionic neurons. The latter then releases acetylcholine
that activate muscarinic receptors of target cells.
Acetylcholine is also the principal neurotransmitter in all autonomic ganglia. In
the autonomic nervous system, acetylcholine is actually released by all pre- and