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

体温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会导致全身热平衡的严重破坏。长时间暴露在炎热的环境/过程中和/或进行剧烈运动会使身体变热，导致体内体温显著上升。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，以增加全身的热量损失。这种反应的固有概念是调节体内体温的设定点。人体的体温调节中心位于中枢神经系统的下丘脑。这个中枢的输入来自皮肤和身体内部核心区域的温度敏感感受器。皮肤和/或核心温度的变化启动了一系列旨在增强散热的生理行动。这种热量通过接触冷空气和汗液产生而失去，汗液蒸发时会使你的身体降温。然而，当身体不能通过出汗来降温时，可能会发生几种由热引起的疾病，如热应激或热衰竭，以及更严重的中暑，并可能导致死亡。与热损失反应的热控制(即，通过皮肤和/或核心温度的变化)无关，越来越多的证据表明，非热因素可以对身体在热应激期间散热的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、代谢性感受器、机械感受器等)激活有关的因素。以及个人因素，如性别、衰老、适应等。然而，关于非热对人体散热的影响机制，人们知之甚少。我提出的研究计划旨在了解在与环境和代谢(运动)热负荷上升相关的热挑战期间，这些因素对人体热平衡的单独和联合贡献。为了更深入地了解非热因素可能发挥的作用，我们将从局部和全身两个角度研究非热调节人体热损失反应的机制。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随这些不同因素的变化。此外，为了更好地了解人类对热应激反应的整合和协调(相互作用)，体温调节功能的评估也将与不同生理系统的同步测量平行进行。通过了解环境和代谢热负荷的精确组合，其中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理解热应激是如何发展的。这些信息将为我们社会的许多部门，包括军队、工业、体育组织和普通公众带来重要的实际利益。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开发，这些新技术和解决方案将提高行业流程效率(例如通风和制冷、现场冷却技术、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.).