Physiology

• What is the function of the sino-atrial node in the heart?


  It generates electrical impulses.
• What happens when the electrical impulse spreads through the cardiac tissue in the atria?


  It causes contraction of the atria.
• Where does the impulse go after the atria?


  To the atrio-ventricular node.
• What is the role of the Bundle of His in the heart's conduction system?


  It transmits the action potential to the Purkinje fibres.
• What occurs after the ventricles contract?


  The atria and ventricles relax, allowing the heart to refill with blood.
• What is the cardiac cycle?


  • The mechanical events of one heartbeat
  • Alternating contraction and relaxation of the myocardium
  • Takes approximately 0.8 seconds
  • Has two distinct phases: diastole and systole
• What is cardiac diastole?


  It is the relaxation of the cardiac muscle.
• What happens during diastole in the heart?


  All heart muscle is relaxed, and all valves are closed.
• What causes the atrio-ventricular valves to open during diastole?


  The pressure in the atria becomes greater than in the ventricles.
• What is atrial systole?


  It is the contraction of the atria.
• What happens during ventricular systole?


  The ventricle walls contract, and the atrio-ventricular valves close.
• What is the first heart sound known as?

  It is known as "Lub".
• What occurs when the pressure in the ventricles exceeds arterial pressure?


  The semi-lunar valves open, and blood is ejected into the arteries.
• What is the second heart sound known as?

  It is known as "Dub".
• What are the phases of the cardiac cycle?


  1. Cardiac diastole: relaxation of the heart muscle
  2. Atrial systole: contraction of the atria
  3. Ventricular systole: contraction of the ventricles
• What happens during atrial diastole?


  Both atria relax and fill with blood.
• What causes the atrio-ventricular valves to open during atrial diastole?


  The pressure in the atria exceeds the pressure in the ventricles.
• What is the Frank-Starling mechanism?


  It states that a greater end-diastolic volume increases the contractile strength of the ventricles.
• What does stroke volume depend on?


  Venous return and ventricular elasticity & contractility.
• What is end-diastolic volume?


  It is the volume of blood in the ventricles at the end of the relaxation phase.
• What is end-systolic volume?


  It is the volume of blood in the ventricles after contraction.
• What is the equation for stroke volume?

  Stroke Volume = End Diastolic Volume - End Systolic Volume.
• What are the key terms related to exercise intensity?

  • Sub-max: Low to moderate intensity within a performer’s aerobic capacity
  • Maximal: High intensity of exercise above a performer’s aerobic capacity that induces fatigue
• How does stroke volume respond to exercise?


  It slightly increases during submaximal exercise and plateaus at 40%-60% of max.
• Why does stroke volume plateau during maximal exercise?


  Increased heart rate does not allow enough time for the ventricles to completely fill with blood.
• What happens to cardiac output during exercise?


  Cardiac output increases in line with exercise intensity and plateaus during maximal exercise.
• What are the average heart rate, stroke volume, and cardiac output at rest for untrained individuals?


  • HR: 70-72 bpm
  • SV: 70 ml
  • CO: 5 l/min
• What are the average heart rate, stroke volume, and cardiac output at maximal exercise for trained individuals?


  • HR: 220-age
  • SV: 160-200 ml
  • CO: 30-40 l/min
• What is blood pressure?


  It is the force of blood on the vessel wall.
• What happens during the systolic phase of blood pressure?


  Blood pressure is high during the contraction phase.
• What happens during the diastolic phase of blood pressure?


  Blood pressure is low during the relaxation phase.
• How can high blood pressure affect blood vessels over time?


  • It can damage the vessel walls.
  • It increases the risk of cardiovascular diseases.
  • It can lead to complications such as heart attack or stroke.