Production of heat from exothermic chemical reactions, especially in the skeletal muscles and certain internal organs, is one of the variable quantities by which homeothermic organisms can regulate their core temperatures. At high external temperatures and during heavy physical labor the formation of heat becomes more and more of a handicap, since performance of mechanical work by the muscles is always connected with an unavoidably high production of heat, amounting to two to ten times their mechanical energy, depending on the efficiency (Lehmann, 1953). Even in the absence of external work or cold exposure a relatively large amount of heat is produced, which, when measured under certain standard conditions (rest, calm, neutral external temperature, psychological relaxation), is designated as basal metabolism. Its determination in animals is often difficult due to uncertainty that the condition of “rest” is satisfied. Basal metabolism is appreciably higher than the level needed to maintain body temperature in a warm environment. Consequently it is not determined by a requirement for heat (cf. “surface area law”, p. 531).
KeywordsBrown Adipose Tissue Heat Production Cold Exposure Cervical Spinal Cord Basal Metabolism
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