1. 13 - 1 Chapter 12 The Cardiovascular System: The Heart

2. The Heart’s Role pulmonary circuit systemic circuit  Blood flows from the heart through the pulmonary circuit (lungs) or systemic circuit (blood vessels)  Vessel types:  Arteries  Arteries (carry blood away from heart)  Veins  Veins (carry blood towards the heart)  Capillaries  Capillaries (connect arteries & veins) atria ventricles  Two atria (upper chambers) & two ventricles (lower chambers)

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4. 12-1: The Heart pericardial cavity  Heart surrounded by pericardial cavity pericardium  Lined by pericardium  Pericardium divisions:  Visceral pericardium  Visceral pericardium: covers surface of the heart  Parietal pericardiumpericardial sac  Parietal pericardium: lines pericardial sac around heart 13 - 4

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6. Surface Anatomy of Heart auricles  Atria seen as auricles on surface of heart  Base  Base—top of the heart  Connects to great vessels (aorta)  Apex  Apex—bottom point of the heart 13 - 6

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8. The Heart Wall  Three layers:  Epicardium  Epicardium—covers outer surface of heart  Myocardium  Myocardium—muscular wall of heart  Endocardium  Endocardium—inner surfaces of heart  Cardiac muscle cells  Striated, one nucleus, many mitochondria intercalated discs  Fused with other cardiac cells at intercalated discs 13 - 8

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10. Internal Anatomy & Organization interatrial septum interventricular septum  Atria separated by interatrial septum; ventricles separated by interventricular septum superior vena cava inferior vena cava  R atrium receives blood from superior vena cava & inferior vena cava tricuspid valve  Blood flows from R atrium into R ventricle tricuspid valve 13 - 10

11.  Chordae tendinae papillary muscles  Chordae tendinae connect valves to papillary muscles inside ventricle  Prevent backflow into atrium pulmonary trunk pulmonary valve  Blood flows from R ventricle to pulmonary trunk through the pulmonary valve pulmonary arteries  Blood leaves heart through pulmonary arteries & enters lungs 13 - 11

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13. pulmonary veins  L atrium receives blood from the lungs through pulmonary veins mitral valve  Blood flows from L atrium into L ventricle through mitral valve ascending aorta aortic valve  Blood flows from L ventricle to ascending aorta through the aortic valve aortic arch  Blood leaves heart through aortic arch & enters body 13 - 13

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15. Heart Valves tricuspid bicuspid  Atrioventricular (AV) valves (tricuspid & bicuspid) regurgitation  Prevent backflow of blood (regurgitation) into atria  Ventricles contract & open valves pulmonary aortic  Semilunar valves (pulmonary & aortic)  Between ventricles & pulmonary trunk or aorta  Prevent backflow of blood into ventricles 13 - 15

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17. Blood Supply to the Heart  Coronary circulation  Coronary circulation supplies blood to heart muscle  Coronary arteries  Coronary arteries branch off of aorta  Infarct  Infarct—interruption in blood flow causes tissue to die  Myocardial infarct (MI) heart attack  Myocardial infarct (MI)—blocked coronary artery (heart attack) 13 - 17

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19. Before Stent After Stent

20. 12-1 Checkpoint: 1.Damage to the semilunar valve of the R ventricle would affect blood flow into which vessel? 2.What prevents the AV valves from swinging into the atria? 3.Why is the L ventricle more muscular than the R ventricle? 13 - 20

21. 12-2: Heartbeat & ECGs Heartbeat  Heartbeat uses contractile cells & conducting system for blood flow Contractile Cells  Triggered to contract when action potential causes muscle twitch to occur  Causes heart to contract & valves to open 13 - 21

22. The Conducting System automaticity  Cardiac muscle contracts on its own (automaticity)  Conducting system  Conducting system—specialized cells that distribute electrical impulses  Nodal cells  Nodal cells—establish heart rate  Conducting cells  Conducting cells—distribute stimulus to heart muscle 13 - 22

23.  Pacemaker cells sinoatrial (SA)  Pacemaker cells in sinoatrial (SA) node determine heart rate  Path of impulse through heart: Path of impulse SA node  atrioventricular (AV) node  AV bundle  L & R bundle branches  Purkinje fibers 13 - 23

24. 13 - 24 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

25. The Electrocardiogram  Electrocardiogram (ECG)  Electrocardiogram (ECG)—records electrical activity of heart  Examining ECG helps determine heart’s performance leads  Heart monitor leads show an ECG as a series of waves  P wave QRS wave T wave  P wave (first wave), QRS wave (second wave), T wave (third wave)  No electrical activity seen as a flatline

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27.  Arrhythmias  Arrhythmias—abnormal patterns of heart activity  Tachycardia  Tachycardia—abnormally fast HR  Bradycardia  Bradycardia—abnormally slow HR  Fibrillation  Fibrillation—heart is quivering, not sending electric impulse  Asystole  Asystole—no electric impulse 13 - 27

28. 13 - 28 Bradycardia Normal Sinus Tachycardia

29. 13 - 29 Ventricular tachycardia Ventricular fibrillation Asystole

30. 13 - 30 Skipped Heart Beat Indicates Heart Attack AV Block

31. 12-2 Checkpoint: 1.If the cells of the SA node were not functioning, how would the heart rate be affected? 2.What are the waves of an ECG? 3.How does bradycardia differ from tachycardia? 13 - 31

32. 12-3: Cardiac Cycle Cardiac cycle  Cardiac cycle—period between the start of one heartbeat & the start of the next systole diastole  Consists of systole (contraction) & diastole (relaxation)  Blood moves from area of high pressure to area of low pressure 13 - 32

33. Phases of the Cardiac Cycle Cardiac CycleCardiac Cycle  Phases of systole & diastole  Atria contract & fill ventricles with blood  Atria relax & ventricles contract  Blood flows into pulmonary trunk & aorta  Ventricles relax & atria fill with blood Heart Sounds Heart Sounds  Heart sounds accompany actions of heart valves  “Lubb-dupp” sound

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35. 12-3 Checkpoint: 1.Provide the alternative terms for contraction & relaxation of heart chambers. 2.Is the heart always pumping blood when the ventricles are filling with blood? 3.What events cause the “lupp-dupp” heart sounds as heard with a stethoscope? 13 - 35

36. 12-4: Cardiac Output Stroke volume (SV)  Stroke volume (SV)—amount of blood ejected by a ventricle in a single beat  Cardiac output (CO)  Cardiac output (CO)—amount of blood pumped by L ventricle in 1 minute  Varies due to activity level  Regulated by blood volume reflexes, nervous system & hormones 13 - 36

37. Blood Volume Reflexes  Atrial reflex  Atrial reflex—adjusts heart rate due to increase in venous blood flow to heart  More venous blood = faster heart rate (HR)  Filling time  Filling time—length of time ventricles fill with blood  Faster HR = less filling time  More blood filling ventricles = more blood pumped out

38. Autonomic Innervation  Pacemaker cells can be modified by nervous system  Epinephrine (E) & norepinephrine increase HR cardiac centers  Medulla oblongata cardiac centers  Cardioacceleratory center  Cardioacceleratory center—increase HR  Cardioinhibitory center  Cardioinhibitory center—decrease HR

39. 12-4 Checkpoint: 1.Define cardiac output. 2.If the cardioinhibitory center of the medulla oblongata were damaged, how would the heart be affected? 3.What effect does increased venous return have on stroke volume? 4.Why is it a potential problem when the heart beats too rapidly?