Question

Refer to the given figure in which A refers to pulmonary artery pressure and B refers to right ventricular pressure. Identify P, Q, R and S in the figure and match with the list (i - iv) given below.
(i) Isovolumetric ventricular contraction.
(ii) Ventricular ejection
(iii) Isovolumetric ventricular relaxation
(iv) Ventricular filling

• A. P- iv, Q - iii, R - ii, S - i
• B. P- ii, Q - iii, R - i, S - iv
• C. P- iv, Q - i, R - ii, S - iii
• D. P- i, Q - ii, R - iii, S - iv

Answer 1

Answer: (C)

P- iv, Q - i, R - ii, S - iii

At the end of the atrial systole, the ventricular systole starts. The ventricular chamber is filled with blood. As the chamber begins to contract, the intraventricular pressure begins to rise. Backflow of blood is prevented by atrioventricular valves and this is responsible for the production of the 1st heart sound. The ventricle now contracts isometrically as a closed chamber, which raises the intraventricular pressure sharply. Duration is about 0.05 sec.

Ejection phase: When the intraventricular pressure increases beyond 80 mm Hg then ejection of blood from the ventricular chamber starts, ventricular muscle fibres starts relaxing.

So, the correct answer is 'P-iv, Q- i, R- ii, S-iii'.