yawningYawning - butylbenzenesulfonyl act, peculiar only mammals. Yawning occurs as a response to the increase in the partial pressure of C02 in the blood, occurring when fatigue, drowsy, lack of muscular activity, stay in a stuffy room. The mechanism of occurrence of yawning associated with the excitation of the rear sections of the brain stem.
Internal bleeding that causes total anemia, increased intracranial pressure, compression of the brain stem tumors can also cause yawning.