Skip to main content
Pearson+ LogoPearson+ Logo
Back

Cardiac Cycle quiz #1

Control buttons has been changed to "navigation" mode.
1/13
  • What are the main phases of the cardiac cycle, and what occurs during each phase?
    The cardiac cycle consists of four main phases: ventricular filling (ventricles relax and fill with blood, AV valves open, semilunar valves closed), isovolumetric contraction (ventricles begin to contract, all valves closed, pressure rises), ventricular ejection (ventricles contract fully, semilunar valves open, blood ejected, AV valves closed), and isovolumetric relaxation (ventricles relax, all valves closed, pressure falls).
  • How do pressure changes in the ventricles control the opening and closing of heart valves during the cardiac cycle?
    When ventricular pressure exceeds atrial pressure, AV valves close; when ventricular pressure exceeds arterial pressure, semilunar valves open. As ventricular pressure falls below arterial pressure, semilunar valves close; when it falls below atrial pressure, AV valves open.
  • What causes the 'lub-dub' sounds of the heartbeat, and which valves are involved in each sound?
    The 'lub' (first heart sound) is caused by the closing of the AV (atrioventricular) valves at the start of ventricular systole. The 'dub' (second heart sound) is caused by the closing of the semilunar valves at the start of ventricular diastole.
  • What is the significance of isovolumetric contraction and isovolumetric relaxation in the cardiac cycle?
    During isovolumetric contraction and relaxation, all heart valves are closed, so no blood moves in or out of the ventricles. These phases allow pressure to build (contraction) or fall (relaxation) without changing ventricular volume.
  • How does an electrocardiogram (ECG) relate to the mechanical events of the cardiac cycle?
    The ECG shows electrical activity: the P wave corresponds to atrial depolarization (atrial systole), the QRS complex to ventricular depolarization (ventricular systole), and the T wave to ventricular repolarization (ventricular diastole). These electrical events trigger the mechanical actions of the heart.
  • What is a heart murmur, and what can cause it during the cardiac cycle?
    A heart murmur is an abnormal sound caused by turbulent blood flow, often due to incomplete closure of heart valves or other valve abnormalities. It can occur when blood leaks backward or flows abnormally through the heart.
  • Why are ventricular pressure changes more important than atrial pressure changes in driving the cardiac cycle?
    Ventricular pressure changes are more significant because the ventricles generate the force needed to open and close valves and move blood through the heart and into the arteries, while atrial pressure changes are smaller and less influential.
  • What are the four main phases of the cardiac cycle, and what happens during each phase?
    The four phases are ventricular filling (ventricles relax and fill with blood), isovolumetric contraction (ventricles contract, all valves closed), ventricular ejection (ventricles contract fully, semilunar valves open, blood ejected), and isovolumetric relaxation (ventricles relax, all valves closed, pressure falls).
  • How do changes in ventricular pressure control the opening and closing of the AV and semilunar valves during the cardiac cycle?
    When ventricular pressure exceeds atrial pressure, AV valves close; when it exceeds arterial pressure, semilunar valves open. As ventricular pressure falls below arterial pressure, semilunar valves close; when it falls below atrial pressure, AV valves open.
  • What causes the 'lub-dub' sounds of the heartbeat, and which valves are responsible for each sound?
    The 'lub' is caused by the closing of the AV (atrioventricular) valves at the start of ventricular systole, and the 'dub' is caused by the closing of the semilunar valves at the start of ventricular diastole.
  • What causes the opening and closing of the heart valves during the cardiac cycle?
    The opening and closing of the heart valves are caused by changes in pressure within the heart chambers. When the pressure on one side of a valve exceeds the pressure on the other side, the valve is forced open or closed accordingly.
  • Which heart valves close when their cusps fill with blood, and what is the physiological reason for this closure?
    The semilunar valves (aortic and pulmonary valves) close when their cusps fill with blood. This occurs when ventricular pressure drops below the pressure in the arteries during ventricular diastole, causing blood to flow backward and fill the cusps, which forces the valves to close.
  • During which event of the cardiac cycle is the S2 (second heart sound, 'dub') heard, and what causes it?
    The S2 heart sound is heard at the beginning of isovolumetric relaxation, when the semilunar valves (aortic and pulmonary) close as ventricular pressure falls below arterial pressure.