Question

1. Draw a pressure- volume loop. Indicate the EDV and ESV, where the atrioventricular (bicuspid and tricuspid) valves are open and where the pulmonary and aortic valves are open. Also include the points where systole and diastole begin. Be able to label each section phase 1, 2, 3 or 4 and include the pump cycle name for that phase.

Answer 1

This diagram contains all the points asked in the question.This is a pressure volume loop which corrosponds with the cardiac cycle phase.since we are more concerned with the left ventricle,we read by taking left ventricle(LV) as our source.

As shown cycle can be divided into 4 basic phases(a,b,c,d).Point 1 on the pv loop is the pressure and volume at the end of ventricular filling or diastole(mitral valve close)so represents EDV (end diastolic volume for the left ventricle.

As the ventricle begins to contract isovolumetrically (phase b)mitral valve closes and left ventricular pressure increases but volume remains same,all valves closed(vertical line).

Once LV pressure exceeds aortic diastolic pressure,aortic valve opens and ejection begins(point2,phase c).here LV volume decreases as pressure increases to a peak value and then decreases as the ventricle begins to relax.

When aortic valve closes(point3)ejection ceases and ventricle relaxes isovolumetrically_LVpressure falls but the LV volume remains unchanged,all valves closed(vertical line),this volume at this time is the end systolic volume(ESV).

When LV pressure falls below left atrial pressure,mitral valve opens(point4)and ventricle begins to fill.

The width of loop represents the difference between EDV and ESV, which is the definition of. Stroke volume and the area is ventricular stroke work.