7.5 - The cardiac cycle

Cards (10)

  • What’s it called when the heart relaxes ?
    Diastole
  • Does diastole occur in all chambers at once ?
    Yes
  • Describe what occurs in the heart during diastole
    • Left and right atria fill with blood from the vena cava and pulmonary veins
    • Pressure increases in atria
    • When pressure in atria exceeds ventricular pressure the atrioventricular valves open
    • All walls relax so pressure in ventricles is reduced (less than in aorta and pulmonary artery)
    • So semi-lunar valves are closed
  • Describe what happens in the heart during systole
    • Atrial systole forces blood into ventricles and atrioventricular valves open, but ventricles stay relaxed
    • A pause allows ventricles to fill, increasing pressure
    • Causes atrioventricular valves to close which prevents back flow
    • Ventricular systole occurs, once pressure exceeds the aorta and pulmonary artery, Semi-lunar valves open
    • Blood pumped out
  • What are found in veins that prevent back flow of blood ?
    Pocket valves
  • How are veins squeezed ?
    When skeletal muscles contract during movement
  • What is a valve made of ?
    Flexible, fibrous cusp shaped tissue
  • What are tendinous cords ?
    Inelastic cords of fibrous connective tissue that connect muscles to valve, prevent inversion
  • What is cardiac output ?
    The volume of blood pumped by one ventricle in one minute
  • Equation for cardiac output (CO) ?
    CO = stroke volume x heart rate