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This is the ejection stage of the cardiac cycle; it is depicted (see circular diagram) as the ventricular systole–first phase followed by the ventricular systole–second phase. [2] After ventricular pressures fall below their peak(s) and below those in the trunks of the aorta and pulmonary arteries, the aortic and pulmonary valves close ...
When the ventricles of the heart contract in ventricular systole, the increased blood pressures in both chambers push the AV valves to close simultaneously, preventing the backflow of blood into the atria. Since the blood pressure in the atria is much lower than that in the ventricles, the flaps attempt to evert to the low pressure regions.
Papillary muscles are finger-like projections from the wall of the left ventricle. When the left ventricle contracts, the pressure in the ventricle forces the valve to close, while the tendons keep the leaflets coapting together and prevent the valve from opening in the wrong direction (thus preventing blood flowing back to the left atrium ...
Following Laplace's law, the tension upon the muscle fibers in the heart wall is the pressure within the ventricle multiplied by the volume within the ventricle divided by the wall thickness (this ratio is the other factor in setting the afterload). Therefore, when comparing a normal heart to a heart with a dilated left ventricle, if the aortic ...
Although the ventricular stimulus originates from the AV node in the wall separating the atria and ventricles, the Bundle of His conducts the signal to the apex. Depolarization propagates through cardiac muscle very rapidly. Cells of the ventricles contract nearly simultaneously. The action potentials of cardiac muscle are unusually sustained.
In human physiology, the atria facilitate circulation primarily by allowing uninterrupted venous flow to the heart during ventricular systole. [22] [23] By being partially empty and distensible, atria prevent the interruption of venous flow to the heart that would occur during ventricular systole if the veins ended at the inlet valves of the ...
The papillary muscles of both the right and left ventricles begin to contract shortly before ventricular systole and maintain tension throughout. [1] This prevents regurgitation—backward flow of ventricular blood into the atrial cavities—by bracing the atrioventricular valves against prolapse—being forced back into the atria by the high ...
Myocardial contractility represents the innate ability of the heart muscle (cardiac muscle or myocardium) to contract.It is the maximum attainable value for the force of contraction of a given heart.