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。长时间暴露于高温环境/过程和/或进行剧烈运动会使身体发热，导致体内温度显著升高。为了抵消这种增加，强大和高度发达的行为和自主体温调节反应被激活，以增强全身热损失。这种反应所固有的是设定点的概念，关于该设定点，内部体温被调节。人体的体温调节中枢位于中枢神经系统的下丘脑。这个中心的输入来自皮肤和身体内部核心区域的温度敏感受体。皮肤和/或核心温度的变化引发一系列旨在增强散热的生理作用。这些热量通过与冷空气接触和汗液的产生而损失，汗液蒸发时会冷却身体。然而，当身体无法通过出汗来冷却自己时，可能会发生一些热引起的疾病，如热应激或热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）的热损失的反应，有越来越多的证据表明，非热因素可以对身体的散热能力在热应激的深远影响。这些非热因素包括与身体感觉受体激活相关的因素（即，压力感受器、代谢感受器、机械感受器等）以及个人因素，如性别，年龄，驯化等，但很少有人知道的机制，对人体散热的非热影响。我提出的研究计划旨在了解这些因素在与环境和代谢（运动）热负荷升高相关的人体热平衡热挑战期间的单独和综合贡献。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身体热损失反应的非热调制机制。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设备）来精确测量身体散热能力的变化，这些变化是这些不同因素的函数。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），温度调节功能的评估也将通过不同生理系统的同步测量来实现。通过了解环境和代谢热负荷的精确组合，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如何发展。这些信息将对我们社会的许多部门，包括军事、工业、体育组织和公众产生重要的实际利益。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，以控制或消除热应激条件，并在热应激条件下保护个人/工作人员的健康和安全。此外，这些知识可用于刺激新技术和解决方案的开发，从而提高工业流程效率（例如通风和制冷、局部冷却技术、新服装设计等）。

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.).