医学英语课件Temperature.ppt

Animals such as dogs that do not have numerous sweat glands often “pant” in warm weather. Panting is the rapid movement of air into and out of the upper respiratory passages, where the warm surfaces evaporate large amounts of water. In this way the animal may lose large amounts of heat. A panting dog considerable Heat Loss Through the Urinary and Digestive Tracts When excreted, urine and feces are at body temperature, and their elimination results in a very small amount of heat loss. Regulation of Body Temperature The hypothalamus is responsible for the regulation of body temperature, and is considered the “thermostat” of the body. As the thermostat, the hypothalamus maintains the “setting” of body temperature by balancing heat production and heat loss to keep the body at the set temperature. In order to do this, the hypothalamus must receive information about the temperature within the body and about the environmental temperature. Specialized neurons of the hypothalamus detect changes in the temperature of the blood that flows through the brain. The temperature receptors in the skin provide information about the external temperature changes the body is exposed to. The hypothalamus then integrates this sensory information and promotes the necessary responses to maintain body temperature within the normal range. 皮肤温度感受器负责提供肌体接触到外部温度变化的信息，接着下丘脑将感官信息整合，为使体温维持在正常范围进行必要的反应。 Mechanisms to Increase Heat Loss In a warm environment or during exercise, the body temperature tends to rise, and greater heat loss is needed. This is accomplished by vasodilation in the dermis and an increase in sweating. Vasodilation brings more warm blood close to the body surface, and heat is lost to the environment. However, if the environmental temperature is higher than body temperature, this mechanism becomes ineffective. The second mechanism is increased sweating, in which excess body heat evaporates the sweat on the skin surface. As mentioned previously, s