Final answer:
The phases of the cardiac cycle with an open mitral valve and a closed aortic valve occur during late ventricular diastole and the initial phase of early ventricular diastole, leading to the stages of the cardiac cycle when the open mitral and closed aortic conditions are present and align with the late diastolic and early relaxation phase of the ventricles. The correct option is B .
Step-by-step explanation:
The question is inquiring about specific phases of the cardiac cycle when two valves in the heart have particular positions: an open mitral valve and a closed aortic valve. During the cardiac cycle, there are multiple phases, but the phases where these conditions of open mitral and closed aortic valves are met occur during late ventricular diastole, and part of early ventricular diastole—before the ventricular contraction occurs, and right after ventricular ejection is complete.
Understanding the cardiac cycle is essential, as it involves the sequence of events that occur as the heart beats. During late ventricular diastole, the heart muscles relax. This relaxation causes the pressure within the ventricles to decrease, making it lower than that in the atria, which results in the mitral valve (the atrioventricular valve on the left side) opening to allow blood to flow from the atrium into the ventricle. Meanwhile, the aortic valve (a semilunar valve) remains closed since the pressure within the ventricle is not high enough to push blood into the aorta.
The next phase is early ventricular diastole, where the ventricle has just completed contraction and is beginning to relax. Blood has been ejected into the aorta, and as the ventricular pressure falls below that of the aorta, the aortic valve closes to prevent backflow. During this brief period, before the pressure in the ventricles falls below that of the atria, the mitral valve remains open. However, the mitral valve will eventually close as the cardiac cycle progresses to the isovolumic ventricular relaxation phase, where all valves are closed, and there is no change in blood volume in the ventricles.
To answer the student's question directly, the phases associated with an open mitral valve and a closed aortic valve are during late ventricular diastole and the initial phase of early ventricular diastole, before the mitral valve closes and leads into isovolumic relaxation. Therefore, the correct answer to the student's multiple-choice question would be (d) Isovolumetric contraction, reduced ejection, isovolumetric relaxation, with the understanding that 'reduced ejection' refers to the final stage of blood being ejected from the ventricles before the aortic valve closes.