Cardio| S1, S2, and the Cardiac Cycle

1.01. S1, S2, and the Cardiac Cycle. Cardiovascular system reveiew for the USMLE Step 1 exam. Two main heart sounds are s1 and s2, also known as "lub" and "dub" S1 corresponds to closure of the mitral and tricuspid valves S2 corresponds to closure of the aortic and pulmonic valves The pause between s2 and s1 is longer than the pause between s1 and s2 in a normal cardiac cycle Elevated heart rate can make it harder to distinguish the two sounds The noise produced by the valves slamming shut, like a door being slammed shut The Atria contracts before the ventricles, and the mitral and tricuspid valves separate the atria from the ventricles, so they shut first which produces S1 The ventricles contract and push blood through the aortic and pulmonic valves, and These shut after this event producing S2.