Nonshivering Thermogenesis Is an Increase in Basal Metabolic Rate, Caused Especially by the Oxidation of Fats, to Produce Heat

When animals are chronically exposed to cold, they develop the ability to increase metabolic heat production without shiver­ing (nonshivering thermogenesis). This increase in metab­olism is mediated through an increase in thyroxine secretion and the Calorigenic effects of catecholamines on lipids. Table 53-1 shows that fat metabolism is an effective way to produce heat. Brownfat is a specialized vascular, Initochondria- rich fat found between the scapulae of newborn small mammals. Catecholamines increase metabolism in all fats, but particularly in brown fat, and the heal produced is distributed around the body through the bloodstream.