The Reflex and Chemical Control of Respiration

¹ Portland, Oregon

The control of respiration seems to be based on the following factors:

a) An intrinsic rhythm of the respiratory neurones of the medulla oblongata. This rhythm is dependent upon oxygen supply to the neurones involved. It is regulated by both reflex and chemical mechanisms.

b) The chemical regulation of respiration concerns the hydrogen ion content of the respiratory neurones which in turn is dependent upon the carbon dioxide tension of the blood and the rate of flow of blood through the medulla. Variations in blood oxygen tension under normal conditions are not thought to be concerned with direct regulating effects on the respiratory neurones. In severe anoxemia, however, the respiratory neurones are probably directly depressed as a result of anoxia.

c) The reflex control of respiration under normal conditions almost certainly is concerned principally with the Hering-Breuer vagal reflexes. The respiratory neurones may be driven reflexly, however, by impulses from the carotid bodies whose 9th nerve endings are stimulated by severe oxygen want. Similarly, respiration may be driven by impulses coming into the medulla over any afferent neurones as in pain, and over neurones from higher brain centers.