[Physiology of cough]

Cough is a reflex phenomenon occurring when sensitive receptors located in the larynx and upper airways are activated. These receptors generate information which reaches the central nervous system. The central organization of the cough reflex loop is poorly understood. The afferent pathways originate in receptors situated under and between airway epithelial cells. Most are rapidly adapting receptors (RAR) linked to myelinized fibers of the vagus nerve which can be directly stimulated by cough-inducing agents. Other receptors generate information carried by non-myelinized C fibers. When activated, these receptors release neuropeptides leading to neurogenic inflammation which can also activate RARs. The threshold of the cough reflex and its expression thus depends on a complex interaction between RARs and C fiber receptors with peripheral and central components. A better understanding of the mechanisms triggering cough and its control would be most useful for optimal management of patients with cough problems.