1. The Cardiovascular System
The Heart
Chapter 20

2. Location
The heart lies in the mediastinum.

3. Pericardium and Layers of Heart Wall

4. Chambers and Sulci

6. Chambers and Sulci

7. Right Atrium

8. Right Ventricle

9. Left Atrium

10. Left Ventricle

11. Anterior Heart

12. Myocardial Thickness and Function
Thickness of myocardium varies according to the function of the chamber

13. Atrioventricular Valves

14. Blood Circulation
Blood flow
Blue: deoxygenated
Red: oxygenated

15. Coronary Circulation

16. Coronary Artery Disease

17. Coronary Artery Disease

18. Coronary Artery Disease

19. Cardiac Muscle Histology

20. Conducting System Autorhythmic cells – self excitable
Reduced permeability of K+, but no change in permeability to Na+.
Na+ continues to diffuse in.
Unstable resting potential – continuously depolarizes, drifting slowly toward threshold. (pacemaker potential)

21. Physiology of Contraction
Potentials initiated by conducting fibers stimulate contractile fibers.

22. Electrocardiogram (ECG/EKG)

23. EKG

24. Cardiac Rhythm and Rate
Normal heart rate: beats/min
Avg. heart beat at rest: beats/min
Sinus tachycardia: > 100 beats/min
Sinus bradycardia: < 60 beats/min

25. Cardiac Rhythm and Rate
Arrhythmias: abnormal rhythm resulting from a defect in the heart conduction system.
Fibrillation: rapid and irregular contractions. Can be atrial or ventricular.
Defibrillation: electrical shock to depolarize myocardium.
Ectopic Focus: a region of the heart, other than the conducting system, that causes and abnormal depolarization.
Junctional rhythm: AV node becomes pacemaker
Heart block: an arrhythmia that occurs when electrical pathway between the atria and ventricle is blocked.

26. EKG

27. Cardiac Cycle
Systole: contraction
Diastole: relaxation

28. Heart sounds
Lubb AV valves close Dupp - semilunar valves close

29. Stroke volume = end diastolic volume - end systolic volume
Stroke Volume (SV)
Volume of blood pumped out by a ventricle with each beat
Stroke volume = end diastolic volume - end systolic volume
SV = EDV - ESV
EDV = Amount of blood that collects in a ventricle during diastole
ESV = Amount of blood remaining in a ventricle after contraction
SV depends on amount of stretch produced by venous return.
Averages about 70 ml/beat
Anything that influences heart rate or blood volume influences venous return and therefore SV

30. Cardiac output = Heart rate x Stroke volume
Cardiac Output (CO)
amount of blood pumped by each ventricle in one minute
Cardiac output = Heart rate x Stroke volume
CO = HR x SV
HR = beats per minute
SV = volume of blood pumped out by a ventricle with each beat

31. Factors Affecting SV Preload
Degree of stretch on the heart before it contracts
Greater preload increases the force of contraction
Frank-Starling law of the heart – the more the heart fills with blood during diastole, the greater the force of contraction during systole
Preload proportional to end-diastolic volume (EDV)
2 factors determine EDV
Duration of ventricular diastole
Venous return – volume of blood returning to right ventricle

32. Factors Affecting SV Contractility
Strength of contraction at any given preload
Positive inotropic agents increase contractility
Often promote Ca2+ inflow during cardiac action potential
Increases stroke volume
Epinephrine, norepinephrine, digitalis
Negative inotropic agents decrease contractility
Anoxia, acidosis, some anesthetics, and increased K+ in interstitial fluid

33. Factors Affecting SV Afterload
Pressure that must be overcome before a semilunar valve can open
Increase in afterload causes stroke volume to decrease
Blood remains in ventricle at the end of systole
Hypertension and atherosclerosis increase afterload

34. Regulation of Heart Rate
1. Autonomic regulation
2. Chemical regulation
3. Other Factors

35. Cardiac Output
Change stroke volume and/or heart rate

36. Homeostatic Imbalance of CO
Congestive heart failure - occurs when the pumping ability of the heart is inadequate to provide normal circulation to meet body needs.
Pulmonary congestion - left side failure
Peripheral congestion - right side failure