Body Temperature Regulation: The processes of heating and cooling that an organism uses to control its temperature.Body Temperature: The measure of the level of heat of a human or animal.Temperature: The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.Skin Temperature: The TEMPERATURE at the outer surface of the body.Sweating: The process of exocrine secretion of the SWEAT GLANDS, including the aqueous sweat from the ECCRINE GLANDS and the complex viscous fluids of the APOCRINE GLANDS.Hypothermia: Lower than normal body temperature, especially in warm-blooded animals.Cold Temperature: An absence of warmth or heat or a temperature notably below an accustomed norm.Pyrogens: Substances capable of increasing BODY TEMPERATURE and cause FEVER and may be used for FEVER THERAPY. They may be of microbial origin, often POLYSACCHARIDES, and may contaminate distilled water.Fever: An abnormal elevation of body temperature, usually as a result of a pathologic process.Hypothalamus: Ventral part of the DIENCEPHALON extending from the region of the OPTIC CHIASM to the caudal border of the MAMMILLARY BODIES and forming the inferior and lateral walls of the THIRD VENTRICLE.Hot Temperature: Presence of warmth or heat or a temperature notably higher than an accustomed norm.Hypothalamus, Anterior: The front portion of the HYPOTHALAMUS separated into the preoptic region and the supraoptic region. The preoptic region is made up of the periventricular GRAY MATTER of the rostral portion of the THIRD VENTRICLE and contains the preoptic ventricular nucleus and the medial preoptic nucleus. The supraoptic region contains the PARAVENTRICULAR HYPOTHALAMIC NUCLEUS, the SUPRAOPTIC NUCLEUS, the ANTERIOR HYPOTHALAMIC NUCLEUS, and the SUPRACHIASMATIC NUCLEUS.Circadian Rhythm: The regular recurrence, in cycles of about 24 hours, of biological processes or activities, such as sensitivity to drugs and stimuli, hormone secretion, sleeping, and feeding.