Chemoreflexes in Breathing

Abstract

The author emphasizes that chemoreceptors are only those for which the adequate stimulus is a chemical factor within possible physiological limits. He deals in this review with those which regulate respiration in man, mentioning other mammals only incidentally. Carbon dioxide can stimulate reflex effects upon ventilation either through the arterial chemoreceptors or by direct action upon the respiratory centers, though the relative importance of the two methods remains debatable. Changes in oxygen concentration, on the other hand, affect the respiratory centers only indirectly, through stimulation of the arterial chemoreceptors. The work discussed includes studies upon premature and full-term newborns and babies, and upon adults exposed for short and long terms to high altitude. The existence of hypothetical chemoreceptors in the veins, heart, alveoli, pulmonary circulation, or the vascular bed of extremities has not been demonstrated, but there does appear to be a chemoreceptor system in the cerebrospinal fluid space, apparently near the lateral recess of the fourth ventricle, though its structure, function, and exact locale remain uncertain.