Temperature regulation in man--a theoretical study.

Abstract

For purposes of theoretical analysis of experimental results and evaluation of hypothetical concepts a mathematical model of thermoregulation in man is presented. The human body is represented by three cylinders: the head, the trunk, and the extremities. Each cylinder is divided into two or more concentric layers to represent anatomical and functional differences in so far as they are of primary importance in thermoregulation. Heat flow between adjacent layers is by conduction, and all layers exchange heat by convection with a central blood compartment. All three skin layers exchange heat with the environment by conduction, convection, radiation, and evaporation. Signals which are proportional to temperature deviations in the brain and to deviations in average skin temperature are supplied to the regulator portion of the model. The regulator then causes evaporative heat loss, heat production by shivering or changes in the peripheral blood flow to occur in the appropriate locations in the body. If a proposed mechanism of thermoregulation is expressed in quantitative form it describes the relationships between the input signals and the resulting thermoregulatory response; the model can be used to compare the quantitative response resulting from a proposed mechanism with the responses obtained by measurement. A number of experimental results are compared with predictions furnished by the mathematical model using a regulator with an output which is proportional to the product of the input signals. It is emphasized that models of this type should be used in close connection with an experimental program to attain their full usefulness.