Basic Principles of the Cardiovascular System

1. Basic Principles of the Cardiovascular System W. Lynne Clarke, Ed.D., RN

2. Objectives • Describe the structures of the heart. • Explain the pumping mechanism of the heart and the path of blood flow through the heart. • Distinguish between pulmonary circulation and systemic circulation. • List the components of the conduction system and the sequence of impulse origination. • State four properties of cardiac cells.

3. Anatomy of the Heart • 4 chambered pump • Weighs less than 1 pound • Size of closed fist • Located in mediastinum – between lungs, sternum, spine

5. Chambers

6. Question • The right side of the heart pumps just as much blood as the left side – why are the walls of the right side thinner than those of the left?

7. Where are these valves? • Tricuspid valve • Mitral valve • Pulmonary semilunar valve • Aortic valve

8. Valves

9. Chordae tendoneae

10. Heart Layers

11. Heart Layers • Endocardium – layer of smooth cells that line heart • Myocardium – layer of muscle that cause contraction (myocardial infarction) • Epicardium – fatty layer that protects heart • Pericardial sac – holds heart in place, reduces friction of beat

12. Circulation • Pulmonary • Systemic • Coronary

13. Pulmonary Circulation

14. Pulmonary Circulation

15. Systemic Circulation

16. Coronary Circulation

17. Coronary Circulation

18. Anterior (A) and posterior (B) views of epicardial coronary circulation. LAD indicates left anterior descending coronary artery; AIV, anterior interventricular vein; CFX, circumflex coronary artery; RCA, right coronary artery; GCV, great cardiac vein; PDA, posterior descending artery; CS, coronary sinus; MCV, middle coronary vein; and SCV, small coronary vein. Coronary Circulation

20. Question • Where and when do coronary arteries fill?

21. Question • Where and when do coronary arteries fill? They fill ONLY during diastole from the pressure in the aorta. They branch from the aorta near where the aorta leaves the left ventricle.

22. Question • How can a fast heart rate be harmful to the heart muscle?

23. Question • How can a fast heart rate be harmful to the heart muscle? The only portion of the systole-diastole cycle that can shorten is diastole.

25. Coronary Sinus

26. Blood Vessels • Define the following: • Artery • Arteriole • Vein • Venule • Capillary • Aorta • Vena Cava • Pulmonary artery • Pulmonary vein

27. Question • What vessels, structures and/or organs are included in each type of circulation?

28. Question • Show the path of a drop of blood from the right atrium back to the right atrium. • Be sure to include major vessels, organs, and valves.

29. Cardiac cycle • Series of events that constitute complete heartbeat • Atrial systole - Contraction of atria to pump blood to ventricles • Ventricle systole – contraction of ventricles to pump blood to body • Atrial diastole – the atria begin refilling during ventricular systole • Ventricular diastole – blood from the atria begins refilling the ventricles during atrial systole.

30. Conduction Pathways • Network of conducting tissue • Specialized cells – do not contract • Initiates each heartbeat and controls rhythm

32. Sinoatrial Node • Located in right atrium • Main cardiac pacemaker • Normally generates impulses at rate of 60 to 100 beats per minute

33. Atrioventricular Node • Receives impulse via internodal pathways • Located in floor of atrium near septum • Delay the impulse to allow ventricular filling • Intrinsic rate 40 to 60 • Two basic functions • Protect ventricles from fast heart rate that may originate in atrium • Serves as pacemakers if SA node fails

34. AV Bundle or Bundle of His • Conducts impulse from AV Node • Intrinsic rate 40 to 60 • Divides into right and left bundle branches at intraventricular septum • Right bundle branch supplies right ventricle • Left bundle branch splits • Anterior supplies upper portion of left ventricle • Posterior supplies lower portion of left ventricle

35. Purkinje Fibers • Enlarged fibers • Spread along septum toward apex and over lateral walls of ventricles • Work with Bundle of His and bundle branches to contract ventricles • Intrinsic rate 20 to 40 • May act as backup pacemaker

36. Cardiac Electrical System

37. Cool Website! • http://science.howstuffworks.com/environmental/life/human-biology/heart4.htm

38. Special Properties of Cardiac Cells • Automaticity – ability to generate own impulse and maintain rhythmic activity • Excitability – ability of all heart cells to respond to impulse • Conductivity – cardiac cell able to relay impulse to neighboring cells and create wave of excitation • Contractility – ability to respond to electrical impulse with pumping action

39. Two Types of Cardiac Cells • Capable of contraction • Capable of conduction

40. Contraction of the Heart • Cell membrane must be electrically activated • Depolarization - Positive ions move into cell and negative ions move out of cell • Repolarization – negative ions return to inside of cell and positive ions move out of cell • This movement of ions is recorded by EKG

41. Cardiac Terminology

42. EKG Representation of Heartbeat

43. The Normal Electrocardiogram

44. Detection and Recording • Transmembrane potential – electrical difference between the inside and outside of the cell • Action potential – changes that occur during the process of depolarization and repolarization within a cell as activated by electrical impulse • Refractory period – time during which the cell is unable to respond to a stimulus • Vector – path of impulse displaying the direction and magnitude of the electrical current

45. Normal Heart • Vector proceeds in same sequence • Vector is predictable

46. EKG machine • Writing arm • Recording device (galvanometer) • Stylus needle responds by heat or pressure • Lead wires • Attaches electrodes to machine • Electrodes • Provides direct contact with skin

47. EKG • Tracing of electrical voltage produced by continual depolarization and repolarization of heart • Shows direction and magnitude of electrical current produced by the heart

48. Waves Deflections from the baseline Designated as: P, QRS, T

49. Waves • P wave – depolarization of atria • Q wave – (may be absent) activation in intraventicular septum, first negative deflection of QRS • R wave – impulse progression through right and left ventricles, first upward deflection of QRS • S wave – completion of left ventricular activation • T wave – repolarization of ventricles

50. Waves