Chapter 34 - Neural and Humoral Control

Abstract

Airway nerves and circulating hormones often regulate the airways and have a significant influence on airway smooth muscle tone, airway blood flow, and mucus secretion. They also play an integral role in the inflammatory process and host defense. Increasing evidence suggests that neural and humoral mechanisms play an important role in the pathophysiology of asthma and chronic obstructive pulmonary disease (COPD). Neural control of airway function is complex. Many neurotransmitters have been identified that act on a multitude of autonomic receptors. There is a close interrelationship between inflammation and neural responses in the airways because inflammatory mediators may influence the release of neurotransmitters via the activation of sensory nerves leading to reflex effects and via stimulation of prejunctional receptors that influence the release of neurotransmitters. In turn, neural mechanisms influence the nature of the inflammatory response, either reducing inflammation or exaggerating the inflammatory response. Humoral mechanisms play an important role in the regulation of airway tone in diseased states of the airways such as asthma and COPD. Adrenaline influences bronchomotor tone and helps in maintaining resting airway tone in asthma patients. It also acts to counteract exercise-induced asthma.