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A ligature placed either around the junction between the sinus venosus and atrium of the frog or turtle heart (first stannius ligature) or around the atrioventricular junction (second stannius ligature); demonstrates that the cardiac impulse is conducted from sinus venosus to atria to ventricle, but that successive chambers possess automaticity ...
In order to relate the work of the heart to skeletal muscle mechanics, Frank observed changes in diastolic pressure with varying volumes of the frog ventricle. His data was analyzed on a pressure-volume diagram, which resulted in his description of peak isovolumic pressure and its effects on ventricular volume. [5]
“The heart will pump what it receives”- Starling’s law of the heart. The Frank–Starling mechanism describes the ability of the heart to change its force of contraction (and, hence, stroke volume) in response to changes in venous return. In other words, if the end-diastolic volume increases, there is a corresponding increase in stroke ...
In a healthy heart all activities and rests during each individual cardiac cycle, or heartbeat, are initiated and orchestrated by signals of the heart's electrical conduction system, which is the "wiring" of the heart that carries electrical impulses throughout the body of cardiomyocytes, the specialized muscle cells of the heart.
An increase in sympathetic stimulation to the heart increases contractility and heart rate. An increase in contractility tends to increase stroke volume and thus a secondary increase in preload. An increase in preload results in an increased force of contraction by Starling's law of the heart; this does not require a change in contractility.
Electrical waves track a systole (a contraction) of the heart. The end-point of the P wave depolarization is the start-point of the atrial stage of systole. The ventricular stage of systole begins at the R peak of the QRS wave complex; the T wave indicates the end of ventricular contraction, after which ventricular relaxation (ventricular diastole) begins.
The trabeculae carneae and the papillary muscles make up a significant percentage of the ventricular mass in the heart (12-17% in normal human adult hearts), and are correlated with ventricular end diastolic volume. [5] Trabeculae ratios of capillary-to myocyte differ between the walls of the right and left ventricle.
Ringer's solution is named after Sydney Ringer, who in 1882–1885 determined that a solution perfusing a frog's heart must contain sodium, potassium and calcium salts in a definite proportion if the heart is to be kept beating for long.