From Big Medical Encyclopedia

YAWNING — the involuntary respiratory movement consisting of a deep slow breath widely open mouth and a bystry vigorous exhalation. Is followed by the characteristic sound caused by vibration of phonatory bands, and in certain cases the movements of a pandiculation in the person, and at animals a perestupaniye of legs and a flexure of a back. 3. represents the bezuslovnoreflektorny act, eurysynusic among mammals, reptiles and fishes, has the adaptive value directed to improvement of supply of an organism with oxygen. During yawning there is a raspravleniye of the fallen-down alveoluses, the surface of lungs increases.

Normal 3. comes at exhaustion, drowsiness, stay in the room with the increased maintenance of CO 2 , after the period weakened breath , in the absence of muscle performance etc. 3. — phylogenetic the ancient form of breath close to deglutitory breath (at reptiles and fishes) arising during the easing of activity of a respiratory center. Central mechanism 3. it is studied insufficiently. By data elektrofiziol, researches 3. it can be caused by irritation of subthalamic area near the III ventricle — between a precomissure and a funnel. 3. is caused also conditional reflex, easily arising as the imitative act. In the conditions of pathology 3. — symptom of air hunger of trunk formations of a brain. In surgical practice 3. — one of the menacing symptoms of the concealed internal hemorrhage which led to an acute anemia. 3. it can be observed during attacks of migraine, at attacks of small epilepsy. Yawning spasms — deep noisy breaths with dacryagogue and the increased salivation are observed at neuropathies and organic diseases of c. N of page.

Bibliography: Lagutina N. I. Reaction: yawning as conditioned excitator Fiziol, zhurn. USSR, t. 40, No. 1, page 23, 1954; Sketches on physiology of a fruit and the newborn, under the editorship of V. I. Bodyazhina, page 54, M., 1966; P e y p e r And. Features of activity of a brain of the child, the lane with it. page 315, L., 1962.

E. L. Golubeva