Note: The diagram at right (and in Fig. 2.05) assumes that by changing afterload, preload remains constant. In the real world this is not the case. As blood is pumped into the aorta and the arterial tree in decreasing amounts, blood volume "backs up" in the veins, ie. preload increases. With increasing preload, the point at which the mitral valve closes, moves up the smooth filling curve at the bottom - it will not remain constant as the simplified diagram shows. You might like to draw a new diagram that reflects what actually takes place.