Solaro R J
Department of Physiology and Biophysics, Collge of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612-7342, USA.
Am J Physiol. 1999 Dec;277(6 Pt 2):S155-63. doi: 10.1152/advances.1999.277.6.S155.
In this paper I present some ideas related to teaching cardiac pump dynamics and regulation to first-year medical students. I emphasize explicit presentation of the relation between the activity of the contractile machine in the myocytes to pump dynamics, pressure-volume relations, and cardiac output regulation, with matching oxygen supply to tissue demands serving as a focal point. Important ideas here are 1) the concept that regulation is at the cellular level of regulation; 2) that force and shortening properties of the cells are ultimately dependent on the number of cross bridges reacting with the thin filament and on the rate of cross-bridge cycling; 3) that the concepts of preload, aferload, and contractility originated in studies of muscle mechanics; 4) that there is a reserve of force-generating cross bridges, i.e., the myofilaments are not fully activated by Ca2+ in the basal state, and that force-generating cross bridges can themselves activate the thin filament; and 5) that length dependence of myofilament Ca2+ activation is important in the cellular basis of Starling's law of the heart. The elaboration of these processes serves to elucidate how these mechanisms play a role in coupling tissue oxygen demands to supply.
在本文中，我提出了一些与向一年级医学生讲授心脏泵血动力学及调节相关的观点。我强调要明确阐述心肌细胞中收缩机制的活动与泵血动力学、压力 - 容积关系以及心输出量调节之间的关系，并以使氧气供应与组织需求相匹配作为重点。这里的重要观点包括：1）调节是在细胞水平上进行的这一概念；2）细胞的力和缩短特性最终取决于与细肌丝反应的横桥数量以及横桥循环的速率；3）前负荷、后负荷和收缩性的概念源自肌肉力学研究；4）存在产生力的横桥储备，即肌丝在基础状态下未被Ca2+完全激活，且产生力的横桥自身可激活细肌丝；5）肌丝Ca2+激活的长度依赖性在心脏Starling定律的细胞基础中很重要。对这些过程的详细阐述有助于阐明这些机制如何在将组织氧气需求与供应相耦合中发挥作用。
