Contractility is defined as the heart's natural force of contraction during which phase?

Contractility is defined as the heart's natural force of contraction during which phase?

• A. Diastole
• B. Isovolumetric contraction
• C. Systole
• D. Atrial contraction

Answer: (C)

Contractility is the heart’s intrinsic ability to generate force with its muscle fibers. That force is produced when the ventricles actively contract, which is during ventricular systole. During systole the heart builds pressure and shortens its muscle fibers to eject blood into the aorta and pulmonary artery. Diastole is the relaxation phase when the heart fills; atrial contraction aids filling but is not where the heart’s main contractile force is expressed. Isovolumetric contraction is a part of systole where the ventricles contract with all valves closed to raise pressure, but the overall phase where contraction happens is systole.

Contractility is the heart’s intrinsic ability to generate force with its muscle fibers. That force is produced when the ventricles actively contract, which is during ventricular systole. During systole the heart builds pressure and shortens its muscle fibers to eject blood into the aorta and pulmonary artery. Diastole is the relaxation phase when the heart fills; atrial contraction aids filling but is not where the heart’s main contractile force is expressed. Isovolumetric contraction is a part of systole where the ventricles contract with all valves closed to raise pressure, but the overall phase where contraction happens is systole.