body Temperature

Temperature, body, measurement of body heat in animals. Warm-blooded animals (including human beings, other mammals, and birds) are able to maintain a fairly constant body temperature, which does not significantly fluctuate with the temperature of the environment. Body temperature in warm-blooded animals may change slightly over the course of a day: an adult human being's normal temperature, 98.6°F (37.0°C), may be slightly lower in the morning and slightly higher by late afternoon. In warm-blooded animals, body temperature is controlled by the hypothalamus, a part of the brain that includes autonomic regulatory centers. The workings of the hypothalamus enable warm-blooded animals to balance the amount of heat lost to the environment with the heat produced by burning food. Cold-blooded animals, including reptiles, cannot regulate body temperature this way and must use other methods to maintain it. For example, snakes lie in the sun or shade, depending on whether they need to raise or lower their body temperature.