Question

Imagine the moment when the heart ventricles begin to contract. At this moment, what is happening with ECG, the heart sounds, the ventricular blood volume, and the tricuspid/bicuspid as well as the semilunar valves? Also, describe how ventricular contraction and blood ejection are affected by mitral regurgitation and by aortic stenosis.

Answer 1

a. When the electrical impulses reach the ventricles through the AV node these impulses are shown as Q, R and S waves pn the Electrocardiogram(ECG). This is also known as QRS complex. This complex last for 0.10 second.

b. During the start of ventricular contraction the atrioventricular valves - mitral valve and tricuspid valve close by a sudden shut to produce the sound LUB. ​​​​​​

c. The ventricular blood volume reduced during ventricular systole. Since the blood gets pumped to the various body parts. The ventricular blood volume reduces from 120ml to 50 ml in a average adult. 50 ml is the residual ventricular volume(RVV) that is always present n ventricles. 120ml is the end diastolic volume(EDV) that is the amount of blood i na loaded ventricle

d. Just when the ventricle receive stimulation for contraction so does the papillary muscle. Thus these muscle stretch chordae tendinae that forms atrioventricular valves in a parachute pattern. This prevent back flow of blood into atrium as soon as the blood is pumped by the ventricles. Thus the mitral valve and the tricuspid valve prevent back flow of blood into the atriums. On the other hand the semilunar valve opens to provide way to the blood in the aorta during ventricular contraction.

e. Mitral regurgitation is a phenomenon in which the blood flows back into atria while ventricular systole. This cause ventricular hypertrophy. The stress on the lest ventrical increases. This causes increase in left ventricle blood pressure and cause systolic failure. Blood ejection occurs in a very odd manner. The blood in ventricles during the systole is pumped to the aorta. But apart from aorta the blood also flows back to the atriums. Thus complete blood is not pumped into the aorta.

f. Aortic stenosis is a disease of failure of aortic orifices which causes narrow of the aortic valves. It also causes ventricular hypertrophy that leads to thick of the walls of left ventricles. The volume of the left ventricle also increase unusually. Due to narrowing of the valves the blood is unable to get pumped with full volume from the heart to the aorta. Thus partial blood flow occurs due to narrowing of the valves. This decrease the blood ejection whic leads to dropping of the blood pressure and deficiency of blood in veins.

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