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The Cardiovascular System

The Cardiovascular System. The Heart. Chapter 20. Location. The heart lies in the mediastinum. Pericardium and Layers of Heart Wall. Chambers and Sulci. Chambers and Sulci. Right Atrium. Right Ventricle. Left Atrium. Left Ventricle. Anterior Heart. Myocardial Thickness and Function.

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The Cardiovascular System

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  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

  5. Chambers and Sulci

  6. Right Atrium

  7. Right Ventricle

  8. Left Atrium

  9. Left Ventricle

  10. Anterior Heart

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

  12. Atrioventricular Valves

  13. Blood Circulation • Blood flow • Blue: deoxygenated • Red: oxygenated

  14. Coronary Circulation

  15. Coronary Artery Disease

  16. Coronary Artery Disease

  17. Coronary Artery Disease

  18. Cardiac Muscle Histology

  19. 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)

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

  21. Electrocardiogram (ECG/EKG)

  22. EKG

  23. Cardiac Rhythm and Rate Normal heart rate: 60-100 beats/min Avg. heart beat at rest: 70-72 beats/min Sinus tachycardia: > 100 beats/min Sinus bradycardia: < 60 beats/min

  24. 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 arrhythmiathat occurs when electrical pathway between the atria and ventricle is blocked.

  25. EKG

  26. Cardiac Cycle Systole: contraction Diastole: relaxation

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

  28. 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

  29. 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

  30. 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

  31. 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

  32. 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

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

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

  35. 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

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