THE THERMOSTATIC CONTROL OF HUMAN METABOLIC HEAT PRODUCTION

Abstract

By cranial thermometry combined with indirect and direct calorimetry, the 2 mechanisms of human "chemical" and "physical" temperature regulation have been experimentally resolved in terms of metabolic, sudomotor, and vasomotor responses of reproducible magnitude to the degree of cold-stimulation at thermoreceptive nerve endings of the skin and warm-stimulation of an extremely sensitive, centrally located thermoreceptive organ. The simplest possible neuroanatomical basis for explanation of the facts observed is discussed with reference to the findings of classical experimental neurosurgery. The function of the "heat maintenance center" in the posterior hypothalamus is synaptic, relaying activity of increasing frequency from thermoreceptive endings in the skin for increasing response by metabolic heat production. This center is indifferent to the stimulus of temperature. The "heat loss center" in the anterior hypothalamus, however, acts as a terminal receptor organ for temperature, comparable to the retina, the anatomically related receptor organ for light. This organ controls not only the direct responses to heat by vasodllation and sweating but also through a third efferent pathway, afferent to the "heat maintenance center," it indirectly controls, with counteracting impulses, the response by metabolic heat production to cold-stimulation of the skin. The result of this threefold function is a thermostatic performance of astonishing power and precision.