L5: Cardiovascular system (anatomy of the heart)

• What is the approximate length of the human heart?

  15 cm
• What is the approximate mass of the human heart?

  300 g
• What is the approximate stroke volume of the human heart?

  70 ml
• How many beats does the human heart make per year?

  38 million/year
• Why is the left ventricle thicker than the right ventricle?

  It forces blood against more resistance
• Why are the atria thinner than the ventricles?

  Ventricular filling is done by gravity
• What are the layers of the heart?

  • Myocardium: main heart muscle
  • Epicardium: visceral layer of serous pericardium
  • Endocardium: lining of chambers
• Where does the left main coronary artery arise from?

  Left side of the aorta
• What are the two branches of the left main coronary artery?

  LAD and circumflex
• What is the function of the pulmonary valve?

  From right ventricle to lung
• What is the function of the aortic valve?

  From left ventricle to body
• What does the mitral valve separate?

  Left atrium and left ventricle
• What does the tricuspid valve separate?

  Right atrium from right ventricle
• How do atrioventricular valves open?

  Pressure from blood fills atria
• What happens when the ventricles contract regarding AV valves?

  AV valves close due to pressure
• What prevents AV valve flaps from everting into atria?

  Contraction of papillary muscles
• When do semilunar valves open?

  When ventricles contract and pressure rises
• What causes semilunar valves to close?

  Intraventricular pressure falls
• What connects heart valves to papillary muscles?

  Chordae tendineae
• What is S1 in heart sounds?

  Closing of AV valves
• What is S2 in heart sounds?

  Closing of semilunar valves
• What is the length of a sarcomere?

  1.8-2.0 micrometres
• What does the A-band in a sarcomere represent?

  Anisotropic (actin & myosin)
• What does the I-band in a sarcomere represent?

  Isotropic (actin)
• What is the Z-line composed of?

  α-actinin
• How long are thick filaments?

  1.6 micrometres
• What is the diameter of thick filaments?

  11 nanometres
• What are thin filaments composed of?

  Actin
• How long are thin filaments?

  1.05 micrometres
• What is the diameter of thin filaments?

  6 nanometres
• What powers the sliding filament mechanism?

  ATP hydrolysis
• What triggers muscle contraction?

  Calcium ion release
• What are the steps of the sliding filament mechanism?

  1. Release (caused by ATP binding)
  2. Conformational change (triggered by ATP hydrolysis)
  3. Rebinding (caused by phosphate dissociation)
  4. Power stroke (caused by ADP dissociation)
• What prevents actin and myosin from interacting at rest?

  Troponin and tropomyosin proteins
• What happens when calcium ions bind to troponin?

  It allows actin-myosin interaction
• What are the phases of the cardiac cycle?

  1. Atrial contraction
  2. Isovolumetric contraction
  3. Rapid ejection
  4. Reduced ejection
  5. Isovolumetric relaxation
  6. Rapid filling
  7. Reduced filling
• What occurs during atrial contraction?

  Valves between atria and ventricles open
• What happens during isovolumetric contraction?

  All valves are closed
• What occurs during rapid ejection?

  Blood flows from ventricles into arteries
• What happens during reduced ejection?

  Ventricle repolarizes and tension reduces