Human thermoregulation: separating thermal and nonthermal effects on the body's capacity to dissipate heat

温度调节是人类生存的一个重要方面，因为体内温度的相对较小的偏差可能导致全身热平衡的严重破坏。长时间暴露在炎热的环境/过程和/或进行剧烈运动可以使身体变热，导致体内温度显著升高。为了抵消这种增加，激活了强大且高度发达的行为和自主热调节反应，以增强全身热损失。这种反应所固有的是人体内部温度被调节的设定点的概念。人体的温度调节中枢位于中枢神经系统的下丘脑。输入到这个中心的信息来自皮肤和身体内部核心区域的温度敏感感受器。皮肤和/或核心温度的变化引发了一系列旨在增强散热的生理活动。这些热量通过与冷空气的接触和汗水的产生而流失，汗水的蒸发使你的身体冷却。然而，当身体无法通过出汗来冷却自己时，就会发生几种由热引起的疾病，如中暑或中暑衰竭，以及更严重的中暑，并可能导致死亡。独立于热控制（即通过皮肤和/或核心温度的变化）的热损失反应，越来越多的证据表明，在热应激期间，非热因素可以对身体的散热能力产生深远的影响。这些非热因素包括那些与身体感觉受体（即压力感受器、代谢感受器、机械感受器等）的激活有关的因素，以及个人因素，如性别、年龄、适应环境等。然而，对人体散热的非热影响机制知之甚少。我提出的研究计划旨在了解这些因素在热挑战期间对与环境和代谢（运动）热负荷升高相关的人体热平衡的单独和综合贡献。为了进一步了解非热因素可能发挥的作用，我们将从局部和全身的角度研究人体热损失反应的非热调节机制。我们将使用世界上唯一的全身热量计（一种测量身体散发热量的装置）来精确测量这些不同因素对人体散热能力的影响。此外，为了更好地了解人体对热应激反应的整合和协调（相互作用），热调节功能的评估也将通过同时测量不同生理系统来并行进行。通过了解环境和代谢热负荷的精确组合，即身体散热能力的生理差异与这些非热因素有关，我们可以开始更好地了解热应激是如何发展的。这些信息将对我们社会的许多部门，包括军事、工业、体育组织和公众有重要的实际好处。通过了解热控制器和非热控制器对人体体温调节的相互作用，我们可以开发/改进管理工具来控制或消除热应激条件，并在热应激条件下保护个人/工人的健康和安全。此外，这些知识可以用来刺激新技术和解决方案的发展，这将提高工业流程效率（例如通风和制冷，现场冷却技术，新的服装设计等）。

Temperature regulation is a vital aspect of human survival as relatively small deviations in internal body temperature can lead to profound disruptions in whole-body heat balance. Prolonged exposure to hot environments/processes and/or performing strenuous exercise can heat the body causing significant increases in internal body temperature. To offset this increase powerful and highly developed behavioral and autonomic thermoregulatory responses are activated to enhance whole-body heat loss. Inherent to this response is the concept of set-point about which internal body temperature is regulated. The body’s temperature regulatory center is located in the hypothalamus of the central nervous system. Input to this center comes from temperature sensitive receptors in both the skin and the internal core regions of the body. Changes in skin and/or core temperature initiates a series of physiological actions aimed at enhancing heat dissipation. This heat is lost by contact with cool air and by sweat production, which cools your body as the sweat evaporates. However, when the body is unable to cool itself by sweating, several heat-induced illnesses such as heat stress or heat exhaustion and the more severe heat stroke can occur, and can result in death. Independent of thermal control (i.e., by changes in skin and/or core temperatures) of heat loss responses, there is increasing evidence demonstrating that nonthermal factors can have profound consequences on the body’s ability to dissipate heat during heat stress. These nonthermal factors include those associated with the activation of the body’s sensory receptors (i.e., baroreceptors, metaboreceptors, mechanoreceptors, etc.) as well as personal factors such as sex, aging, acclimation, etc. However, little is known about the mechanism underlying the nonthermal influence on human heat dissipation. My proposed study program is directed at understanding the separate and combined contribution of these factors during thermal challenges to human heat balance associated with elevations in environmental and metabolic (exercise) heat load. To achieve an advanced understanding of the role that nonthermal factors may play, we will study the mechanisms underlying the nonthermal modulation of the body’s heat loss response from both a local and whole-body perspective. We will use the world’s only whole-body calorimeter (a device for measuring heat emitted by the body) to precisely measure changes in the body's capacity to dissipate heat as function of these different factors. Moreover, in order to acquire a better understanding of the integration and coordination (interplay) of the human response to heat stress, the evaluation of thermoregulatory function will also be paralleled by the simultaneous measures of different physiological systems. By understanding the precise combination of environmental and metabolic heat loads where physiological differences in the body’s capacity to dissipate heat occur in relation to these nonthermal factors, we can begin to develop a better understanding of how heat stress develops. Such information will have important practical benefits for many sectors of our society including the military, industry, sporting organizations and the general public. By understanding the interplay between thermal and nonthermal controllers on human thermoregulation, we can develop/improve management tools to control or eliminate heat stress conditions and protect the health and safety of individuals/workers during heat-stress conditions. Moreover, this knowledge can be used to stimulate the development of new technologies and solutions that will improve industry process efficiencies (e.g. ventilation and refrigeration, spot cooling techniques, new clothing designs, etc.).