INTERACTION OF CARDIOVASCULAR REFLEXES IN THERMAL STRAIN

热应变中心血管反射的相互作用

• 批准号: 2459949
• 负责人: GARY W MACK
• 金额: $ 22.36万
• 依托单位: JOHN B. PIERCE LABORATORY, INC.
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-09-30 至 1999-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2459949
• 关键词: aerobic exercise; antiadrenergic agents; baroreceptors; baroreflex; blood circulation; body temperature regulation; body water dehydration; cardiovascular function; carotid artery; electrocardiography; flame photometry; heat; heterodyning; human subject; oral pharyngeal; physical fitness; physiologic stressor; radioimmunoassay; skin circulation; sweat; sympathetic nervous system; syncope; vasoconstriction; water drinking behavior

It is well documented that aerobic exercise training provides an individual with a pronounced thermoregulatory and circulatory advantage during exercise in the heat. The ability to prevent excessive hyperthermia during conditions of high thermal and circulatory strain is dependent on a complex interaction between reflexes that regulate heat dissipating mechanisms and non-thermoregulatory (circulatory) reflexes. The long-term objectives of this project are to describe the physiological mechanisms involved in the interaction between control systems which regulated arterial blood pressure and those which regulate body temperature. We are particularly interested in baroreflex control of cutaneous vasoconstrictor activity and how it is influenced by thermal status and/or physical fitness. Our specific aims of over the next five years are: l) to characterize spatial heterogeneities in baroreflex mediated cutaneous vasoconstriction 2) to demonstrate attenuated baroreceptor mediated increases in sympathetic vasoconstrictor activity in hyperthermic humans. 3) to identify the mechanism by which thermoregulatory responses to thermal stress are attenuated by baroreceptor unloading. 4) to examine the role of oropharyngeal reflexes in reversing the inhibitory influence of dehydration on heat loss mechanisms in thermally stressed humans. To accomplish these goals we will create topographical perfusion maps of relatively large areas of the skin microvasculature with the aid of a computer-guided stereotaxic laser Doppler velocimetry system, monitor sympathetic vasoconstrictor nerve activity directly via microneurographic techniques, and modify local sympathetic adrenergic responses in the skin with selective adrenergic blocking agents. We will relate the circulatory and thermoregulatory responses (i.e. changes in sympathetic nerve activity, skin blood flow, or sweating) to their primary physiological stimuli (i.e. changes in central venous or carotid artery pressure or body core temperature). We expect to demonstrate that baroreflex control of circulatory function is altered by the thermal status of the individual and is dependent, in part, on their level of aerobic fitness. In addition, we expect to demonstrate that the interaction between baroreceptor and thermoregulatory control of skin blood flow occurs at a site more proximal than the cutaneous arterioles. Thermal status will be manipulated using passive heating and/or exercise while baroreceptor mediated increases in sympathetic nerve activity will be accomplished by application of lower body negative pressure and/or carotid neck pressure. These studies should improve our understanding of the control of arterial blood pressure during conditions of thermal stress and provide new knowledge about the mechanisms that humans employ to resist syncope in conditions of high circulation and thermal stress.

有充分的证据表明，有氧运动训练提供了 具有明显体温调节和循环优势的个体 在炎热的天气里锻炼。 防止过度的能力 在高热和循环紧张的条件下， 依赖于调节热量的反射之间复杂的相互作用 耗散机制和非温度调节（循环）反射。 该项目的长期目标是描述 生理机制参与控制之间的相互作用 调节动脉血压的系统和调节 体温我们对压力反射控制特别感兴趣 皮肤血管收缩活性以及它如何受到热的影响 状态和/或身体健康。 我们未来五年的具体目标 年是：1）表征压力反射的空间异质性 介导的皮肤血管收缩2），以证明减弱 压力感受器介导的交感血管收缩活性增加 在体温过高的人身上。 3)来确定 对热应激的体温调节反应被以下物质减弱： 压力感受器卸载 4)研究口咽反射的作用 逆转脱水对热量损失的抑制作用 热应激人体的机制。 为了实现这些目标，我们 将创建相对较大区域的局部灌注图。 借助计算机引导的立体定位激光的皮肤微血管 多普勒测速系统，监测交感缩血管神经 活动直接通过显微神经摄影技术，并修改局部 皮肤中的交感肾上腺素能反应， 封闭剂 我们将把血液循环和体温调节 反应（即交感神经活动，皮肤血流量， 或出汗）对他们的主要生理刺激（即， 中心静脉或颈动脉压力或身体核心温度）。 我们 希望证明压力反射控制循环功能是 由个人的热状态改变，并依赖于， 一部分取决于他们的有氧健身水平。此外，我们预计， 表明压力感受器和 皮肤血流的温度调节控制发生在一个部位， 比皮肤小动脉近端。热状态将是 使用被动加热和/或锻炼来操纵，而压力感受器 交感神经活动的介导增加将通过以下方式实现： 施加下体负压和/或颈动脉颈部压力。 这些研究将提高我们对动脉粥样硬化控制的认识。 在热应激条件下的血压，并提供新的 关于人类用来抵抗晕厥的机制的知识， 高循环和热应力条件下。