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The isovolumetric contraction phase lasts about 0.05 seconds, [1] but this short period of time is enough to build up a sufficiently high pressure that eventually overcomes that of the aorta and the pulmonary artery upon opening of the semilunar valves. This process, therefore, helps maintain the correct unidirectional flow of blood through the ...
Then, prompted by electrical signals from the sinoatrial node, the ventricles start contracting (ventricular systole), and as back-pressure against them increases the AV valves are forced to close, which stops the blood volumes in the ventricles from flowing in or out; this is known as the isovolumic contraction stage. [1] [6]
Segment AB is the contraction phase. Since both the mitral and aortic valves are closed, volume is constant. For this reason, this phase is called isovolumic contraction. At point B, pressure becomes higher than the aortic pressure and the aortic valve opens, initiating ejection. BC is the ejection phase, volume decreases. At the end of this ...
A Wiggers diagram modified from [1]. A Wiggers diagram, named after its developer, Carl Wiggers, is a unique diagram that has been used in teaching cardiac physiology for more than a century.
An increase in contractility is manifested as an increase in dP/dt max during isovolumic contraction. However, dP/dt max is also influenced by preload, afterload, heart rate, and myocardial hypertrophy. Hence, the relationship between ventricular end-diastolic volume and dP/dt is a more accurate index of contractility than dP/dt alone.
Cardiac physiology or heart function is the study of healthy, unimpaired function of the heart: involving blood flow; myocardium structure; the electrical conduction system of the heart; the cardiac cycle and cardiac output and how these interact and depend on one another.
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This page was last edited on 17 April 2010, at 20:44 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may ...