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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.
Ventricular systole is the contractions, following electrical stimulations, of the ventricular syncytium of cardiac muscle cells in the left and right ventricles. Contractions in the right ventricle provide pulmonary circulation by pulsing oxygen-depleted blood through the pulmonary valve then through the pulmonary arteries to the lungs.
Consequently, this initial phase of ventricular systole is known as isovolumic contraction, also called isovolumetric contraction. [1] In the second phase of ventricular systole, the ventricular ejection phase, the contraction of the ventricular muscle has raised the pressure within the ventricle to the point that it is greater than the ...
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 ...
Ventricular septal defect: No intensification upon inspiration. VSD is a defect in the ventricular wall, producing a shunt between the left and right ventricles. Since the L ventricle has a higher pressure than the R ventricle, flow during systole occurs from the L to R ventricle, producing the holosystolic murmur.
The fourth heart sound or S 4 is an extra heart sound that occurs during late diastole, immediately before the normal two "lub-dub" heart sounds (S 1 and S 2).It occurs just after atrial contraction and immediately before the systolic S 1 and is caused by the atria contracting forcefully in an effort to overcome an abnormally stiff or hypertrophic ventricle.
A blood volume increase would cause a shift along the line to the right, which increases left ventricular end diastolic volume (x axis), and therefore also increases stroke volume (y axis). The Frank–Starling law of the heart (also known as Starling's law and the Frank–Starling mechanism ) represents the relationship between stroke volume ...
During the ventricular contraction portion of the cardiac cycle, the Purkinje fibers carry the contraction impulse from both the left and right bundle branch to the myocardium of the ventricles. [5] This causes the muscle tissue of the ventricles to contract. This generates force to eject blood out of the heart, either to the pulmonary ...