Abstract
Studies on the physiological functions of the posterior cricoarytenoid muscle were done with special reference to respiratory and protective functions, comparing with those of the diaphragm.
Activity of the posterior cricoarytenoid muscle and the diaphragm seen in every inspiration was reflexly inhibited by electrical stmulation of the internal branch of the superior laryngeal nerve. Duration of this inhibition reduced by increase of PCO2. Respiratory discharges in these two muscles faded away by further increase of PCO2.
Reflex activation of the posterior cricoarytenoid muscle was still observed even after complete disappearance of spontaneous respiratory activities.
These results indicate that the most primitive and the most important function of the larynx may be protection of the lower airway.
