1. Chapter 9 Cardiac Physiology
Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

2. Circulatory System Three basic components Heart Blood vessels Blood
Serves as pump that establishes the pressure gradient needed for blood to flow to tissues
Blood vessels
Passageways through which blood is distributed from heart to all parts of body and back to heart
Blood
Transport medium within which materials being transported are dissolved or suspended
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

3. Circulatory System Pulmonary circulation
Closed loop of vessels carrying blood between heart and lungs
Systemic circulation
Circuit of vessels carrying blood between heart and other body systems
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

4. Circulatory System Anatomy of the heart
Hollow, muscular organ about the size of a clenched fist
Positioned between two bony structures – sternum and vertebrae
Position makes it physically possible to manually drive blood from heart when it is not pumping effectively (CPR)
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

5. Circulatory System Heart Dual pump
Right and left sides of heart function as two separate pumps
Divided into right and left halves and has four chambers
Atria
Upper chambers
Receive blood returning to heart and transfer it to lower chambers
Ventricles
Lower chambers which pump blood from heart
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

6. Circulatory System Heart Arteries Veins Septum
Carry blood away from ventricles to tissues
Veins
Vessels that return blood from tissues to the atria
Septum
Continuous muscular partition that prevents mixture of blood from the two sides of heart
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

7. Circuit of Blood Flow
The venae cavae are veins returning blood to the right atrium. Oxygen has been extracted from this blood. Carbon dioxide has been added to it. This blood is pumped from the right ventricle through the pulmonary artery to the lungs.
The lungs add oxygen to this blood received from the right side of the heart. Carbon dioxide is removed from this blood. This blood flows through pulmonary veins to the left atrium of the heart. This oxygen rich blood is pumped from the left ventricle through the aorta, a large artery.
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

8. Blood Flow Through and Pump Action of the Heart
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

9. Heart Valves Atrioventricular (AV) valves
Right and left AV valves are positioned between atrium and ventricle on right and left sides
Prevent backflow of blood from ventricles into atria during ventricular emptying
Right AV valve
Also called tricuspid valve
Left AV valve
Also called bicuspid valve or mitral valve
Chordae tendinae
Fibrous cords which prevent valves from being everted
Papillary muscles
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

10. Heart Valves Semilunar valves Aortic and pulmonary valves
Lie at juncture where major arteries leave ventricles
Prevented from everting by anatomic structure and positioning of cusps
No valves between atria and veins
Reasons
Atrial pressures usually are not much higher than venous pressures
Sites where venae cavae enter atria are partially compressed during atrial contraction
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

11. Heart Valves
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

12. Heart Wall Consists of three distinct layers Endothelium Myocardium
Thin inner tissue
Epithelial tissue which lines entire circulatory system
Myocardium
Middle layer
Composed of cardiac muscle
Constitutes bulk of heart wall
Epicardium
Thin external layer which covers the heart
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

13. Cardiac Muscle Fibers
Interconnected by intercalated discs and form functional syncytia
Within intercalated discs – two kinds of membrane junctions
Desmosomes
Gap junctions
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

14. Heart is enclosed by pericardial sac Pericardial sac has two layers
Tough, fibrous covering
Secretory lining
Secretes pericardial fluid
Provides lubrication to prevent friction between pericardial layers
Pericarditis
Inflammation of pericardial sac
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

15. Electrical Activity of Heart
Heart beats rhythmically as result of action potentials it generates by itself (autorhythmicity)
Two specialized types of cardiac muscle cells
Contractile cells
99% of cardiac muscle cells
Do mechanical work of pumping
Normally do not initiate own action potentials
Autorhythmic cells
Do not contract
Specialized for initiating and conducting action potentials responsible for contraction of working cells
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

16. Electrical Activity of Heart
Locations of noncontractile cells capable of autorhymicity
Sinoatrial node (SA node)
Specialized region in right atrial wall near opening of superior vena cava
Pacemaker of the heart
Atrioventricular node (AV node)
Small bundle of specialized cardiac cells located at base of right atrium near septum
Bundle of His (atrioventricular bundle)
Cells originate at AV node and enters interventricular septum
Divides to form right and left bundle branches which travel down septum, curve around tip of ventricular chambers, travel back toward atria along outer walls
Purkinje fibers
Small, terminal fibers that extend from bundle of His and spread throughout ventricular myocardium
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

17. Specialized Conduction System of Heart
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

18. Electrical Activity of Heart
Cardiac impulse originates at SA node
Action potential spreads throughout right and left atria
Impulse passes from atria into ventricles through AV node (only point of electrical contact between chambers)
Action potential briefly delayed at AV node (ensures atrial contraction precedes ventricular contraction to allow complete ventricular filling)
Impulse travels rapidly down interventricular septum by means of bundle of His
Impulse rapidly disperses throughout myocardium by means of Purkinje fibers
Rest of ventricular cells activated by cell-to-cell spread of impulse through gap junctions
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

19. Spread of Cardiac Excitation
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

20. Electrical Activity of Heart
Atria contract as single unit followed after brief delay by a synchronized ventricular contraction
Action potentials of cardiac contractile cells exhibit prolonged positive phase (plateau) accompanied by prolonged period of contraction
Ensures adequate ejection time
Plateau primarily due to activation of slow L-type Ca2+ channels
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

21. Electrical Activity of Heart
Ca2+ entry through L-type channels in T tubules triggers larger release of Ca2+ from sarcoplasmic reticulum
Ca2+ induced Ca2+ release leads to cross-bridge cycling and contraction
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

22. Excitation-Contraction Coupling in Cardiac Contractile Cells
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

23. Electrical Activity of Heart
Because long refractory period occurs in conjunction with prolonged plateau phase, summation and tetanus of cardiac muscle is impossible
Ensures alternate periods of contraction and relaxation which are essential for pumping blood
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

24. Relationship of an Action Potential and the Refractory Period to the Duration of the Contractile Response in Cardiac Muscle
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

25. Electrocardiogram (ECG)
Record of overall spread of electrical activity through heart
Represents
Recording part of electrical activity induced in body fluids by cardiac impulse that reaches body surface
Not direct recording of actual electrical activity of heart
Recording of overall spread of activity throughout heart during depolarization and repolarization
Not a recording of a single action potential in a single cell at a single point in time
Comparisons in voltage detected by electrodes at two different points on body surface, not the actual potential
Does not record potential at all when ventricular muscle is either completely depolarized or completely repolarized
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

26. Electrocardiogram (ECG)
Different parts of ECG record can be correlated to specific cardiac events
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

27. Abnormalities in Rate Tachycardia
Rapid heart rate of more than 100 beats per minute
Bradycardia
Slow heart rate of fewer than 60 beats per minute
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

28. Abnormalities in Rhythm
Regularity or spacing of ECG waves
Arrhythmia
Variation from normal rhythm and sequence of excitation of the heart
Examples
Atrial flutter
Atrial fibrillation
Ventricular fibrillation
Heart block
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

29. Cardiac Myopathies Damage of the heart muscle Myocardial ischemia
Inadequate delivery of oxygenated blood to heart tissue
Necrosis
Death of heart muscle cells
Acute myocardial infarction (heart attack)
Occurs when blood vessel supplying area of heart becomes blocked or ruptured
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

30. Representative Heart Conditions Detectable Through ECG
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

31. Cardiac Output Volume of blood ejected by each ventricle each minute
Determined by
heart rate times
stroke volume
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

32. Cardiac Output
Heart rate is varied by altering balance of parasympathetic and sympathetic influence on SA node
Parasympathetic stimulation slows heart rate
Sympathetic stimulation speeds it up
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

33. Cardiac Output Stroke volume
Determined by extent of venous return and by sympathetic activity
Influenced by two types of controls
Intrinsic control
Extrinsic control
Both factors increase stroke volume by increasing strength of heart contraction
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

34. Frank-Starling Law of the Heart
States that heart normally pumps out during systole the volume of blood returned to it during diastole
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

35. Nourishing the Heart Muscle
Muscle is supplied with oxygen and nutrients by blood delivered to it by coronary circulation, not from blood within heart chambers
Heart receives most of its own blood supply that occurs during diastole
During systole, coronary vessels are compressed by contracting heart muscle
Coronary blood flow normally varies to keep pace with cardiac oxygen needs
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

36. Coronary Artery Disease (CAD)
Pathological changes within coronary artery walls that diminish blood flow through the vessels
Leading cause of death in United States
Can cause myocardial ischemia and possibly lead to acute myocardial infarction
Three mechanisms
Profound vascular spasm of coronary arteries
Formation of atherosclerotic plaques
Thromboembolism
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

37. Possible Outcomes of Acute Myocardial Infarction (Heart Attack)
Chapter 9 Cardiac Physiology Human Physiology by Lauralee Sherwood ©2007 Brooks/Cole-Thomson Learning

38. Cardiac Anatomy

39. Cardiac Cycle

40. Conduction