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

Answer: CSolution: The pressure changes in the right ventricle and pulmonary arteries are qualitatively similar to those for the left ventricle and aorta. These are striking quantitative differences, however. Typical pulmonary artery systolic and diastolic pressures are 25 and 10 mm Hg, respectively, compared to systemic arterial pressures of 120 adn 80 mm Hg. Thus the pulmonary circulation is a low-pressure system. Despite the difference in pressure during contraction, however, the stroke volumes of the two ventricles are the same. During isovolumetric contraction and relaxation, the ventricular volume does not change, though the ventricular pressure increases and decreases respectively.