The Heart

• What is the cardiac cycle?

  The cardiac cycle is the sequence of events in which the chambers of the heart contract to pump blood efficiently.
• What are the three main phases of the cardiac cycle?

  • Diastole (filling phase)
  • Atrial systole (contraction)
  • Ventricular systole (contraction)
• What happens during diastole?

  The atria and ventricles are relaxed, allowing blood to flow into the atria from the veins.
• How does blood flow into the ventricles during diastole?

  Blood flows through open AV valves into the ventricles as pressure in the atria increases.
• What remains closed during diastole?

  The semilunar valves remain closed during diastole.
• What occurs during atrial systole?

  The atria contract, causing a small increase in pressure to fill the ventricles.
• What happens during ventricular systole?

  The walls of the ventricles contract, increasing pressure and forcing blood into the arteries.
• What causes the atrioventricular valves to shut during ventricular systole?

  Blood filling the flaps of the atrioventricular valves causes them to shut.
• What happens to the semilunar valves during ventricular systole?

  The semilunar valves open, allowing blood to flow into the arteries.
• What is the relationship between pressure in the atria and ventricles during the cardiac cycle?

  Pressure in the atria is greater than in the ventricles during diastole, and vice versa during ventricular systole.
• What sound is produced during the cardiac cycle?

  The sound "lub dup" is produced by the closing of the atrioventricular and semilunar valves.
• What is myogenic contraction in cardiac muscle?

  Myogenic contraction means that cardiac muscle can initiate its own contraction without external stimulation.
• What is the role of the sino-atrial node (SAN) in the heart?

  The SAN generates electrical impulses to coordinate heart contractions.
• How does the wave of excitation travel through the heart?

  The wave of excitation travels from the SAN over the atria, causing them to contract.
• What is the function of the atrioventricular node (AVN)?

  The AVN delays the wave of excitation to allow the atria to finish contracting and the ventricles to fill with blood.
• What is cardiac output?

  Cardiac output is the amount of blood the heart pumps each minute.
• If a patient has a stroke volume of $60 \text{ cm}^3$ and a heart rate of $85 \text{ bpm}$, what is their cardiac output?


  Cardiac output = $60 \text{ cm}^3 \times 85 \text{ bpm} =$$5100 \text{ cm}^3/\text{min} =$$5.1 \times 10^3 \text{ cm}^3/\text{min}$
• How is cardiac output calculated?

  Cardiac output = stroke volume × heart rate.
• What are the key features of an ECG?

  • Non-invasive and inexpensive
  • Detects heart conditions and abnormalities
  • Sensors attached to the skin pick up electrical activity
  • Converts electrical activity into a trace
• What does a small or unclear P wave indicate on an ECG?

  A small or unclear P wave indicates atrial fibrillation.
• What does elevation of the ST section on an ECG indicate?

  Elevation of the ST section indicates a heart attack.
• What are the signs of tachycardia and bradycardia?

  • Tachycardia: heart beats over 100 bpm at rest
  • Bradycardia: heart beats below 60 bpm at rest
• What is an ectopic heartbeat?

  An ectopic heartbeat is an extra heartbeat that interrupts the regular rhythm.
• What is fibrillation?

  Fibrillation is an irregular heartbeat caused by lack of coordination between the cells of the atria or ventricles.
• What is myocardial infarction?

  • Occurs when cardiac cells are starved of oxygen
  • Necessary for respiration of fatty acids
• What does stroke volume refer to in cardiovascular physiology?

  Stroke volume refers to the volume of blood pumped from the left ventricle during each systolic contraction.
• What is the average stroke volume for an adult male?

  The average stroke volume for an adult male is 70 ml.
• What are the components of a healthy ECG?

  • P wave: excitation of the atria
  • Q, R, S waves: excitation of the ventricles
  • T wave: diastole
• What are the implications of deep S waves on an ECG?

  • Indicates ventricular hypertrophy (thickening of muscle walls)
• What are the implications of diagnosing heart problems using ECGs?

  • Tachycardia: heart beats too fast
  • Bradycardia: heart beats too slowly
  • Ectopic heartbeat: extra heartbeat interrupts rhythm
  • Fibrillation: irregular heartbeat