Clinical temperature. New physiological basis.

Quantitative mechanisms that regulate normal temperature and determine its clinical aberrations have been found with the methods of gradient calorimetry and tympanic thermometry. Homeostasis is achieved by warm-sensitive neurons of a "human thermostat" or "temperature-eye" in the anterior portion of the hypothalamus. These fire and excite sweating and vasodilatation for heat loss when their temperature exceeds a sharply determined set point near 37 C (98.6 F). Similar warm-sensitive neurons inhibit, through a synaptic station in the posterior portion of the hypothalamus, the metabolic response to cold which is excited by cold-receptors of the skin firing from thresholds at 33 to 35 C (91.4 to 95 F). Pyrogens depress or extinguish firing of central thermoreceptors. The set point is shifted. Fever develops. These findings provide a basis for the understanding of clinical temperature, and the tool for its reliable measurement—tympanic, not rectal thermometry.