Brain function critically depends on a close matching between metabolic demands, appropriate delivery of oxygen and nutrients, and removal of cellular waste. This matching requires continuous regulation of cerebral blood flow (CBF), which can be categorized into four broad topics: 1) autoregulation, which describes the response of the cerebrovasculature to changes in perfusion pressure, 2) vascular reactivity to vasoactive stimuli [including carbon dioxide (CO₂)], 3) neurovascular coupling (NVC), i.e., the CBF response to local changes in neural activity (often standardized cognitive stimuli in humans), and 4) endothelium-dependent responses. This review focuses primarily on autoregulation and its clinical implications. To place autoregulation in a more precise context, and to better understand integrated approaches in the cerebral circulation, we also briefly address reactivity to CO₂ and NVC. In addition to our focus on effects of perfusion pressure (or blood pressure), we describe the impact of select stimuli on regulation of CBF (i.e., arterial blood gases, cerebral metabolism, neural mechanisms, and specific vascular cells), the inter-relationships between these stimuli, and implications for regulation of CBF at the level of large arteries and the microcirculation. We review clinical implications of autoregulation in aging, hypertension, stroke, mild cognitive impairment, anesthesia, and dementias. Finally, we discuss autoregulation in the context of common daily physiological challenges, including changes in posture (e.g., orthostatic hypotension, syncope) and physical activity.

中文翻译：

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人类脑血流的调节：自动调节的生理学和临床意义

大脑功能关键取决于代谢需求、氧气和营养物质的适当输送以及细胞废物的清除之间的密切匹配。这种匹配需要脑血流 (CBF) 的持续调节，可分为四大主题：1) 自动调节，描述脑血管系统对灌注压变化的反应，2) 血管对血管活性刺激的反应性 [包括二氧化碳（CO ₂）]，3）神经血管耦合（NVC），即CBF对神经活动局部变化的反应（通常是人类标准化的认知刺激），以及4）内皮依赖性反应。本综述主要关注自动调节及其临床意义。为了将自动调节置于更精确的背景下，并更好地理解大脑循环中的综合方法，我们还简要讨论了对 CO ₂和 NVC 的反应性。除了关注灌注压（或血压）的影响外，我们还描述了选择刺激对 CBF 调节（即动脉血气、脑代谢、神经机制和特定血管细胞）的影响、相互关系这些刺激之间的关系，以及对大动脉和微循环水平 CBF 调节的影响。我们回顾了自动调节对衰老、高血压、中风、轻度认知障碍、麻醉和痴呆的临床影响。最后，我们在常见的日常生理挑战的背景下讨论自动调节，包括姿势的变化（例如，直立性低血压、晕厥）和体力活动。