Temperature Regulation by Hypothalamic Proportional Control with an Adjustable Set Point.

HAMMEL, H. T., D. C. JACKSON, J. A. J. STOLWIJK, J. D. HARDY, AND S. B. STR@MME. Temperature regulation by hypothalamic proportional control with an adjustable set point. J. Appl. Physiol. 18(6): 1146-1154. 1g63.-The role of the hypothalamic and skin temperatures in controlling the thermal response of a resting animal was studied by measurements of I) hypothalamic, rectal, ear skin, and trunk skin temperatures on the resting dog and rhesus monkey in hot, neutral, and cold environments; and 2) the thermal and metabolic responses of a dog in neutral and cold environments during and immediately after holding the hypothalamus at approximately 39.0 C by means of six thermodes surrounding the hypothalamus and perfused with water. The results indicate that I) a resting animal shivers in a cold environment with the same or higher hypothalamic temperature as the same animal in a neutral environment; 2) a resting animal pants in a hot environment with the same or lower hypothalamic temperature as the same animal in a neutral environment; 3) the hypothalamus is nonetheless strongly responsive to an increase or decrease of I C; 4) the rate of heat loss increases at the onset of sleep while the hypothalamic temperature is falling; 5) the hypothalamic temperature is 1-2 C lower during sleep even though thermoregulatory responses are the same as when awake; S) the rate of heat loss decreases upon awakening while the hypothalamic temperature is rising. The discussion of these results includes a suggestion that the set point for temperature regulation is I) decreased by a rising or elevated skin and extrahypothalamic core temperature, 2) increased by a falling or lowered skin and extrahypothalamic core temperature, 3) decreased upon entering and during sleep and is increased upon awakening.