The Cardiac Cycle

• What is the cardiac cycle?

  Series of events in one heart beat
• What is the contraction of the heart called?

  Systole
• What is the relaxation of the heart called?

  Diastole
• How does one cardiac cycle relate to another?

  One cycle follows another continuously
• What happens to blood flow between cardiac cycles?

  There is no gap; blood keeps flowing
• What happens to the volume of a heart chamber during contraction?

  Volume decreases during contraction
• What happens to the volume of a heart chamber during relaxation?

  Volume increases during relaxation
• What is the relationship between volume and pressure changes in the heart?

  Volume changes lead to pressure changes
• What happens to pressure when volume decreases?

  Pressure increases when volume decreases
• What happens to pressure when volume increases?

  Pressure decreases when volume increases
• How do heart valves operate during the cardiac cycle?

  They open and close due to pressure changes
• When do valves open in the heart?

  When pressure behind them is greater
• When do valves close in the heart?

  When pressure in front is greater
• What is the function of heart valves?

  To prevent blood from flowing backwards
• What happens during atrial systole?

  Atria contract, decreasing volume and increasing pressure
• What forces the AV valves open during atrial systole?

  Pressure in the atria rises above ventricles
• What happens to ventricular pressure during atrial systole?

  There is a slight increase in ventricular pressure
• What coincides with atrial systole?

  Ventricular diastole coincides with atrial systole
• What happens during ventricular systole?

  Ventricles contract, decreasing volume and increasing pressure
• What forces the AV valves to close during ventricular systole?

  Pressure in the ventricles rises above atria
• What happens to pressure in the ventricles during ventricular systole?

  Pressure rises above aorta and pulmonary artery
• What happens to the semilunar valves during ventricular systole?

  They open to force blood into arteries
• What coincides with ventricular systole?

  Atrial diastole coincides with ventricular systole
• What happens to the atria during ventricular systole?

  Atria begin to fill with blood again
• What happens during diastole?

  Both ventricles and atria are relaxed
• What forces the semilunar valves to close during diastole?

  Pressure in ventricles drops below aorta
• What happens to the atria during diastole?

  Atria continue to fill with blood
• How does blood return to the heart?

  Via the vena cava and pulmonary vein
• What happens to pressure in the atria during diastole?

  Pressure rises above that in the ventricles
• What forces the AV valves open during diastole?

  Pressure in the atria rises above ventricles
• How does blood flow into the ventricles during diastole?

  Flows passively without need of atrial systole
• What begins the cycle again after diastole?

  Atrial systole begins the cycle again
• Label the correct parts

  A) Open

  B) Closed

  C) Ventricular systole

  D) Closed