The role of the autonomic nervous system in the control of lung ventilation and gas exchange can be considered in two ways. The first is the analysis of primary control mechanisms involving, for example, specific groups of receptors and their afferent nerves in the autonomic nervous system and their reflex action on breathing or on lung effector tissues. This analytical approach has been used extensively in studies with experimental animals, in which it is possible to isolate single components of the control mechanisms and to determine their properties. These studies lead to clear, forthright, and usually reliable statements such as the following: stimulation of pulmonary stretch receptors inhibits breathing and causes bronchodilation; hypoxia has a direct constrictor action on the pulmonary vascular bed; and stimulation of tracheal irritant receptors causes coughing, bronchoconstriction, and hypertension.
However, such statements may have little applicability to conditions in intact animals, in particular man, and