When does the cardiac upstroke occur?

When does the cardiac upstroke occur?

• A. During systole
• B. During diastole
• C. During isovolumetric relaxation
• D. During atrial contraction

Answer: (A)

The rapid rise in the arterial pressure known as the upstroke happens as the ventricle ejects blood into the aorta, which occurs during systole. After the mitral valve closes, the ventricle builds pressure in isovolumetric contraction, but no blood is yet released. Once the ventricular pressure exceeds the aorta, the aortic valve opens and blood is rapidly ejected, producing the steep upstroke of the arterial pressure waveform. Diastole is the relaxation phase when pressure falls, and atrial contraction occurs late in diastole and does not generate the upstroke.

The rapid rise in the arterial pressure known as the upstroke happens as the ventricle ejects blood into the aorta, which occurs during systole. After the mitral valve closes, the ventricle builds pressure in isovolumetric contraction, but no blood is yet released. Once the ventricular pressure exceeds the aorta, the aortic valve opens and blood is rapidly ejected, producing the steep upstroke of the arterial pressure waveform. Diastole is the relaxation phase when pressure falls, and atrial contraction occurs late in diastole and does not generate the upstroke.