Cardiac cycle phases, pressure-volume loops, and baroreceptor reflex mechanisms tested on USMLE Step 1.
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- What event marks the beginning of isovolumetric contraction in the cardiac cycle?
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Closure of the mitral (and tricuspid) valve, marked by the first heart sound (S1)- Why is isovolumetric contraction called 'isovolumetric'?
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Ventricular volume stays constant because both the atrioventricular and semilunar valves are closed while pressure rises- What event ends isovolumetric contraction and begins ventricular ejection?
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Opening of the aortic (and pulmonic) valve, when ventricular pressure exceeds aortic pressure- What event marks the beginning of isovolumetric relaxation?
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Closure of the aortic (and pulmonic) valve, marked by the second heart sound (S2)- Why is isovolumetric relaxation called 'isovolumetric'?
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Ventricular volume stays constant because both the semilunar and atrioventricular valves are closed while pressure falls- What event ends isovolumetric relaxation and begins rapid ventricular filling?
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Opening of the mitral (and tricuspid) valve, when atrial pressure exceeds ventricular pressure- What heart sound, when present, corresponds to rapid ventricular filling and is often a normal finding in children?
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The third heart sound (S3)- What heart sound corresponds to atrial contraction (the atrial 'kick') late in diastole?
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The fourth heart sound (S4)- What is the a wave on the jugular venous pulse (or atrial pressure tracing) caused by?
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Atrial contraction- What is the c wave on the jugular venous pulse caused by?
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Bulging of the tricuspid valve into the right atrium during isovolumetric ventricular contraction- What is the v wave on the jugular venous pulse caused by?
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Atrial filling against a closed tricuspid valve during ventricular systole- What is the x descent on the jugular venous pulse caused by?
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Atrial relaxation and downward pulling of the tricuspid valve during ventricular systole- What is the y descent on the jugular venous pulse caused by?
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Opening of the tricuspid valve and rapid early ventricular filling- What does the width of a pressure-volume loop along the x-axis represent?
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Stroke volume- What does the area enclosed within a pressure-volume loop represent?
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Stroke work performed by the ventricle
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