Bodily Reactions to High Temperature

Abstract

In high environmental temperature, heat is transferred to the body by the physical processes of radiation, convection and conduction, so that ultimately the body temperature rises. Changes in body temperature, whether as a result of severe environmental variation or of infectious, metabolic or toxic agents, produce more or less profound effects on the various biologic processes within the body and on the body systems. The production and rate of locomotion of the leukocytes are increased and a definite leukocytosis occurs. The cardiac changes during hyper-pyrexia include shortening of the P-R interval, increase in heart rate, increase in cardiac output, elevation of fibrillation threhold, and greater tendency for fainting, collapse and even death for those with poor cardiovascular reserve if the environmental temperature becomes high suddenly and is of sufficient duration. Prolonged sojourn in a hot environment increases the plasma concentration of corticosteroids, owing to release of corticotropin (ACTH), which leads to decrease of sodium and chloride in the sweat and greater reabsorption of sodium by the renal tubules. Acclimatization to a hot environment leads to a slower heart rate, lower skin and rectal temperature, and more stable blood pressure, and less discomfort. Adjustments in cardiovascular function and secretion of the sweat glands are important in adaptation to a hot environment. Increased rates of sweating, decreased concentrations of salt in the sweat, altered sensitivity of the thermoregulatory center, and increased blood volume are the various responses in the adjustments of acclimatization. Maintenance of fluid and electrolyte balance are of paramount importance in a hot environment.