Abstract
Human thermoregulatory system is a feedback system that maintains core temperature (Tcore) within normal range. In this system, the central nervous system receives afferent information regarding skin (Tskin) and core temperatures, and then outputs sympathetic nerve activity (SNA) to muscular vessels (Muscle SNA) and skin (Skin SNA). Both SNAs may regulate heat loss. Muscle SNA regulates blood redistribution from central to cutaneous circulations, whereas skin SNA regulates skin blood flow and sweat. However, the transfer function in the central nervous system from Tskin and Tcore to these SNAs remains unclear. To examine the transfer functions, we largely changed environmental room temperature from 0 to 50°C while measuring muscle and skin SNA by microneurography, Tskin, and Tcore. By using 2 input 1 output models, we investigated the transfer function from both Tskin and Tcore inputs to either muscle or skin SNA output. The transfer functions controlling muscle and skin SNAs have following similar characteristics; 1) the gain from Tcore to each SNA was over 10 times larger than that from Tskin to it, 2) the transfer function has high-pass filter characteristics with approximately 20 dB/dec. However, these transfer functions have regionally different characteristics as follows; 1) the transfer gain from either Tskin or Tcore to skin SNA was 2-3 times larger than that to muscle SNA, 2) coherence between both temperature to skin SNA (0.7-0.8) was smaller than that to muscle SNA (0.8-0.9). [Jpn J Physiol 55 Suppl:S62 (2005)]
