energy that raises the temperature of a body or substance; also, the rise of the temperature itself. Heat is associated with molecular motion, and is generated in various ways, including combustion, friction, chemical action and radiation. The total absence of heat is absolute zero, at which all molecular activity ceases.
balance between heat loss and heat production; its maintenance is critical to the patient's survival.
a disorder resulting from overexposure to heat or to the sun. Long exposure to extreme heat or too much activity under a hot sun causes excessive sweating which removes large quantities of salt and fluid from the body. When the amount of salt and fluid in the body falls too far below normal, heat exhaustion may result. The same disease in birds is called heat prostration (below). See also heat stroke (below).
see specific dynamic action.
the heat that a body may absorb without changing its temperature.
body heat can be lost by conduction, convection, evaporation and radiation; evaporation is the critical one during exercise and in hot environments.
caused by exposure to high ambient temperature, especially if the humidity causes hyperthermia in birds. This is exacerbated by their poor heat loss mechanisms.
is one of the functions of the hypothalamus and consists of a balancing of the body's heat loss and heat gain by regulation of respiration, skin temperature, sweating and muscle tone.
heat1 shock proteins
proteins expressed by heat shock (hsp) genes as a result of exposure to increased temperature or other stress. See also heat shock response (below).
heat1 shock response
decreased transcription and translation activity caused by the synthesis of heat shock proteins by an organism as a result of exposure to increased temperatures or other stress.
the number of calories required to raise the temperature of 1 g of a particular substance one degree centigrade.
exposure of the animal to high ambient temperatures.
elevation of body temperature above physiologically active levels due to the production of excessive heat, exposure to excessive ambient temperatures or failure to lose heat. Characterized by restlessness, followed by dullness, weakness and recumbency. There is severe hyperthermia, the animal seeks cool places, is dyspneic and lapses into a coma terminally.
is observed only in experimental application of high temperatures in early pregnancy. Observed defects are of the central nervous system, and of the limbs including arthrogryposis and selective shortening.
in animals is their ability to function well under high environmental temperatures. This capacity varies widely between species and breeds. Much of the difference is due to variations in the capacity to increase heat loss under conditions of heat stress.
the weaning of commercial chickens away from an artificial heat source at about 4 weeks of age.