CONTROL OF SKIN BLOOD-FLOW IN THE NEUTRAL ZONE OF HUMAN-BODY TEMPERATURE REGULATION

In humans, matching of heat loss and heat production in the ''neutral' ' zone, defined operationally in terms of a range of skin temperatures (T-sk), is accomplished by regulation of skin blood flow (SkBF). Our studies were designed to reveal the characteristics of control of SkBF [from measurements of forearm blood flow (FBF)] in this zone. We cont rolled the temperature of water sprayed on most of the body of supine men and women at 33 or 35 degrees C in a square- wave pattern (15 min at each temperature) or a step pattern (60 min at 33 degrees C separat ed by short periods at 35 degrees C). FBF followed T-sk (0.5 ml . min( -1) 100 ml(-1).degrees C-1). Esophageal temperature changed similar to 0.11 degrees C with each 2 degrees C change in T-sk, falling with T-s k increase and vice versa. Little influence on FBF, <0.1 ml . min(-1). 100 ml(-1).degrees C-1, was observed when only the forearm was spraye d with 33 and 35 degrees C water. We conclude that SkBF control in the 33-35 degrees C range of T-sk is dominated by the feedforward reflex influence of T-sk On SkBF. The reflex response overcompensates for the effect of T-sk On thermal balance in the neutral zone, so that equili brium core temperature has an inverse relationship to T-sk.