How do warm-blooded animals keep their temperatures constant?

How do warm-blooded animals keep their temperatures constant? Ans. Warm blooded animals like us keep their temperature constant irrespective of their surroundings. But how do they do that? Energy should be supplied from the inside. I assume that reactions like making ATP from glucose are exothermic. That means in winter our body reacts more. Water is absorbed by those reaction.We should need more water in winter. Which is contradictory with our real life experience. On the other hand what prevents cold blooded animals from making heat? Don't they need ATP? Do they use different types of reactions to make energy? Do they have different evolutionary path? They don't seems very different from us.How do warm blooded animals maintain their body temperature? In some animals, the body temperature remains constant and is independent of the environment. These animals are classified as homeothermic eg. birds and mammals. They can regulate their body temperatures by generating heat through metabolic activities. Hence they are also called as endothermic animals. During summer, the environmental temperature shoots up. Warm blooded animals keep their hairs and feathers flat and close to the body so that there is no air between the body and hair. This permits loss of heat by radiation and prevents the entry of heat in to the body. The sweat glands in the skin are stimulated to secrete sweat which evaporates, taking excess heat from the body, thereby reducing the body temperature. In dogs and cats panting helps to cool down the body temperature. Panting also speeds up evaporation from the lungs. During winter, environmental temperature is low. The hairs and feathers are raised, so that air accumulates between the hair and the body surface. This air gets warmed up by the body temperature. This layer of warmed air functions as an insulator to prevent heat loss from the body. The blood vessels supplied to the skin become constricted in mammals. Hence blood supply to the skin is restricted. At the same time, blood vessels supplied to the main excretory organ namely, kidney become dilated. This results in excess urine formation. Thus urine removes excess heat from the body to keep the temperature constant. This is true as in the case of human beings. Metabolic rate is also increased, so that a large amount of metabolic heat is produced to warm up the body. Source : The Hindu