[The activity of the internal laryngeal muscles during respiration]

Electromyographic study of the laryngeal internal muscles in dogs showed that the character and intensity of the electrical activity are specific for each muscle not only in frequency and amplitude of potentials, but also in the relation to the phases of the breathing cycle. Phasic electrical activity of these muscles occurred either in inspiration or expiration, whereas in some muscles the activity was recorded both in inspiration and expiration. Besides the phasic electrical activity, a less pronounced constant activity in some muscles was observed. The functional value of this phenomenon may be connected with the fixation of the larynx cartilages, whereas that of the phasic activity is connected with the realization of the larynx respiratory function. It was shown that the instrinsic laryngeal muscles activity coordination in the breathing act is not static and strictly determined but has a dynamic character: it can change under various conditions. The final result of the action of the intrinsic laryngeal muscles determining the degree of the glottis opening in the rspective phase of the breathing cycle is conditioned by the simultaneous but differently pronounced and differently derected activity of some of these muscles.