Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark
Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON K1N 6N5, Canada.
J Exp Biol. 2020 Feb 20;223(Pt 4):jeb215335. doi: 10.1242/jeb.215335.
In the 1950s, Arthur C. Guyton removed the heart from its pedestal in cardiovascular physiology by arguing that cardiac output is primarily regulated by the peripheral vasculature. This is counterintuitive, as modulating heart rate would appear to be the most obvious means of regulating cardiac output. In this Review, we visit recent and classic advances in comparative physiology in light of this concept. Although most vertebrates increase heart rate when oxygen demands rise (e.g. during activity or warming), experimental evidence suggests that this tachycardia is neither necessary nor sufficient to drive a change in cardiac output (i.e. systemic blood flow, ) under most circumstances. Instead, is determined by the interplay between vascular conductance (resistance) and capacitance (which is mainly determined by the venous circulation), with a limited and variable contribution from heart function (myocardial inotropy). This pattern prevails across vertebrates; however, we also highlight the unique adaptations that have evolved in certain vertebrate groups to regulate venous return during diving bradycardia (i.e. inferior caval sphincters in diving mammals and atrial smooth muscle in turtles). Going forward, future investigation of cardiovascular responses to altered metabolic rate should pay equal consideration to the factors influencing venous return and cardiac filling as to the factors dictating cardiac function and heart rate.
20 世纪 50 年代，亚瑟·C·盖顿（Arthur C. Guyton）提出，心输出量主要受外周血管调节，从而颠覆了心血管生理学中心脏的核心地位。这一观点有违直觉，因为调节心率似乎是调节心输出量的最明显手段。在这篇综述中，我们根据这一概念考察了比较生理学领域的最新和经典进展。尽管大多数脊椎动物在需氧量增加时（例如在活动或升温期间）会提高心率，但实验证据表明，在大多数情况下，这种心动过速既不是驱动心输出量（即全身血流）变化的必要条件，也不是充分条件。相反，心输出量取决于血管传导性（阻力）和电容性（主要由静脉循环决定）之间的相互作用，而心脏功能（心肌收缩性）的贡献有限且可变。这种模式在所有脊椎动物中都存在；然而，我们也强调了某些脊椎动物群体在潜水性心动过缓期间（即潜水哺乳动物的下腔静脉瓣和海龟的心房平滑肌）为调节静脉回流而进化出的独特适应性。展望未来，对代谢率改变引起的心血管反应的研究应同等考虑影响静脉回流和心脏充盈的因素，以及决定心脏功能和心率的因素。
