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Autonomic defense responses to extremely strong heat stress

对极强热应激的自主防御反应

基本信息

批准号：
61440027
负责人：
NAGASAKA Tetsuo
金额：
$ 9.6万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1989
项目状态：
已结题

项目摘要

We studied thermoregulatory defense responses to extreme heat stress in human subjects. 1. Heat-induced skin vasoconstriction (HIVC). Finger vessels constricted and finger volume decreased when the hand was heated locally to temperature above body core temperature. This vasoconstriction was consistent when the subject was hyperthermic, and was not observed in the forearm skin where arteriovenous anastomoses (AVA) do not exist. HIVC was marked when the subject reported a sharp rise of local thermal sensation. During this period, skin sympathetic nerve activity to the hand increased. Partitional measurements of blood flow through superficial capillaries and deeply located AVA's confirmed that the vascular compartments responsible for HIVC were mainly AVA'S. From these results, we propose that HIVC is a response to retard heat transfer from hot contact objects to the body in already hyperthermic subjects. 2. Selective brain cooling enhanced by inward venous flowing through emissary veins. We confirmed that selective brain cooling via emissary veins such as angular oculi veins (AOV) was an important process enabling brain temperature (indicated by tympanic membrane temperature (T_<ty>)), to become lower than body core temperature in hyperthermic subjects. Mechanical obstruction of flow through AOV resulted an increase in the rise of T_<ty> during whole body warming. Mechanical obstruction of facial veins increased inward flowing of AOV-flow and suppressed the rate of rise in T_<ty>. These results strongly support the idea that emissary veins supply venous blood into the cavernous sinuses which act as a heat sink to cool the brain during hyperthermia in humans.

我们研究了人类受试者对极端热应激的体温调节防御反应。1.热诱导皮肤血管收缩（HIVC）。手指血管收缩和手指体积减少时，手被局部加热到高于身体核心温度的温度。当受试者体温过高时，这种血管收缩是一致的，并且在不存在动静脉硬化（AVA）的前臂皮肤中未观察到。当受试者报告局部热感觉急剧上升时，HIVC明显。在此期间，手部皮肤交感神经活动增加。通过浅表毛细血管和深部AVA的血流分区测量证实，负责HIVC的血管室主要是AVA。从这些结果中，我们建议，HIVC是一种反应，以延迟从热接触物体的身体已经高热科目的热传递。2.通过导静脉的内向静脉流动增强选择性脑冷却。我们证实了通过导静脉如眼角静脉（AOV）进行的选择性脑冷却是使体温过高者的脑温度（以鼓膜温度（T_）表示<ty>）低于体核温度的重要过程。机械性阻断AOV血流可使全身加温时T_1升高幅度增大<ty>。机械性阻塞面静脉可增加AOV-血流的内流，抑制T_1的上升速率<ty>。这些结果有力地支持了这样一种观点，即在人类体温过高时，导静脉向海绵窦供应静脉血，海绵窦作为散热器冷却大脑。