Lecture 02, 3

• What is cardiac output?

  Amount of blood ejected by the heart
• What does stroke volume represent?

  Amount of blood pumped with each heartbeat
• What is the normal stroke volume range?

  50 ml to 100 ml
• What are the determinants of stroke volume?

  Preload, afterload, and contractility
• How is stroke volume calculated?

  SV = EDV - ESV
• What does EDV stand for?

  End-Diastolic Volume
• What does ESV stand for?

  End-Systolic Volume
• What is ejection fraction (EF)?

  Fraction of blood pumped out
• How is ejection fraction calculated?

  EF = (SV / EDV) x 100
• If EDV is 900 ml and ESV is 20 ml, what is EF?

  77%
• What is cardiac output (Q)?

  Amount of blood ejected by the heart per minute
• How is cardiac output calculated?

  Q = stroke volume x heart rate
• If stroke volume is 70 ml and heart rate is 60 bpm, what is Q?

  4200 ml/min
• What is preload?

  Force acting on muscles before contraction
• How does preload affect stroke volume?

  Higher preload increases stroke volume
• What is afterload?

  Force that offers resistance to muscle shortening
• What is total load?

  Preload + afterload
• What does the Frank Starling mechanism describe?

  Contractility is a function of volume
• What is systemic vascular resistance (SVR)?

  How wide or narrow the blood vessels are
• What happens to SVR if cardiac output is low?

  SVR is elevated (vasoconstriction)
• What happens to SVR if cardiac output is high?

  SVR will be low (vasodilation)
• What is the effect of aortic regurgitation on cardiac output?

  Increased cardiac output and lower SVR
• What is afterload's effect on stroke volume?

  Increased afterload decreases stroke volume
• What factors increase afterload?

  Narrowed blood vessels
• What can high afterload lead to?

  Myocardial damage and heart failure
• What are inotropes?

  Agents that alter the force of muscular contractions
• What do negative inotropic agents do?

  Weaken the force of contraction
• What do positive inotropic agents do?

  Increase the strength of contraction
• What effect does ventricular hypertrophy have on inotropic state?

  Increases inotropic state
• What effect does myocardial infarction have on inotropic condition?

  Decreases inotropic condition
• What do negative chronotropic agents do?

  Decrease heart rate
• What do positive chronotropic agents do?

  Increase heart rate
• What neurotransmitter does the parasympathetic system release?

  ACh (acetylcholine)
• What is the effect of activating M2 receptors?

  Decreased force of contraction and bradycardia
• What neurotransmitters mediate sympathetic activation?

  Catecholamines mainly on β1-receptors
• What is the role of baroreceptors?

  Regulate sympathetic and parasympathetic activity
• Where are baroreceptors located?

  Carotid sinus and aortic arch

  
• What does an ECG measure?

  Electrical fields from heart signals

  
• What is the purpose of electrodes in an ECG?

  To pick up electrical signals from the heart
• What does the P wave represent in an ECG?

  Atrial depolarisation