Chapter 20 THE CARDIOVASCULAR SYSTEM: THE HEART

1. 1 Chapter 20THE CARDIOVASCULAR SYSTEM: THE HEART Lecture Outline

2. Principles of Human Anatomy and Physiology, 11e 2 INTRODUCTION The cardiovascular system consists of the blood, heart, and blood vessels. The heart is the pump that circulates the blood through an estimated 60,000 miles of blood vessels. The study of the normal heart and diseases associated with it is known as cardiology.

3. Principles of Human Anatomy and Physiology, 11e 3 Chapter 20 The Cardiovascular System: The Heart Heart pumps over 1 million gallons per year. Over 60,000 miles of blood vessels

4. Principles of Human Anatomy and Physiology, 11e 4 ANATOMY OF THE HEART

5. Principles of Human Anatomy and Physiology, 11e 5 ANATOMY OF THE HEART

6. Principles of Human Anatomy and Physiology, 11e 6 Location of the heart The heart is situated between the lungs in the mediastinum with about two-thirds of its mass to the left of the midline (Figure 20.1). Because the heart lies between two rigid structures, the vertebral column and the sternum, external compression on the chest can be used to force blood out of the heart and into the circulation. (Clinical Application)

7. Principles of Human Anatomy and Physiology, 11e 7 Heart Location Heart is located in the mediastinum area from the sternum to the vertebral column and between the lungs

8. Principles of Human Anatomy and Physiology, 11e 8 Heart Orientation Apex - directed anteriorly, inferiorly and to the left Base - directed posteriorly, superiorly and to the right Anterior surface - deep to the sternum and ribs Inferior surface - rests on the diaphragm Right border - faces right lung Left border (pulmonary border) - faces left lung

9. Principles of Human Anatomy and Physiology, 11e 9 Heart Orientation Heart has 2 surfaces: anterior and inferior, and 2 borders: right and left

10. Principles of Human Anatomy and Physiology, 11e 10 Surface Projection of the Heart Superior right point at the superior border of the 3rd right costal cartilage Superior left point at the inferior border of the 2nd left costal cartilage 3cm to the left of midline Inferior left point at the 5th intercostal space, 9 cm from the midline Inferior right point at superior border of the 6th right costal cartilage, 3 cm from the midline

11. Principles of Human Anatomy and Physiology, 11e 11 Pericardium The heart is enclosed and held in place by the pericardium. The pericardium consists of an outer fibrous pericardium and an inner serous pericardium (epicardium. (Figure 20.2a). The serous pericardium is composed of a parietal layer and a visceral layer. Between the parietal and visceral layers of the serous pericardium is the pericardial cavity, a potential space filled with pericardial fluid that reduces friction between the two membranes. An inflammation of the pericardium is known as pericarditis. Associated bleeding into the pericardial cavity compresses the heart (cardiac tamponade) and is potentially lethal (Clinical Application).

12. Principles of Human Anatomy and Physiology, 11e 12 Pericardium Fibrous pericardium dense irregular CT protects and anchors the heart, prevents overstretching Serous pericardium thin delicate membrane contains parietal layer-outer layer pericardial cavity with pericardial fluid visceral layer (epicardium)

13. Principles of Human Anatomy and Physiology, 11e 13 Layers of the Heart Wall The wall of the heart has three layers: epicardium, myocardium, and endocardium (Figure 20.2a). The epicardium consists of mesothelium and connective tissue, the myocardium is composed of cardiac muscle, and the endocardium consists of endothelium and connective tissue (Figure 20.2c). Myocarditis is an inflammation of the myocardium. Endocarditis in an inflammation of the endocardium. It usually involves the heart valves.

14. Principles of Human Anatomy and Physiology, 11e 14 Layers of Heart Wall Epicardium visceral layer of serous pericardium Myocardium cardiac muscle layer is the bulk of the heart Endocardium chamber lining & valves

15. Principles of Human Anatomy and Physiology, 11e 15 Muscle Bundles of the Myocardium Cardiac muscle fibers swirl diagonally around the heart in interlacing bundles

16. Principles of Human Anatomy and Physiology, 11e 16 Chambers and Sulci of the Heart (Figure 20.3). Four chambers 2 upper atria 2 lower ventricles Sulci - grooves on surface of heart containing coronary blood vessels and fat coronary sulcus encircles heart and marks the boundary between the atria and the ventricles anterior interventricular sulcus marks the boundary between the ventricles anteriorly posterior interventricular sulcus marks the boundary between the ventricles posteriorly

17. Principles of Human Anatomy and Physiology, 11e 17 Chambers and Sulci

18. Principles of Human Anatomy and Physiology, 11e 18 Chambers and Sulci

19. Principles of Human Anatomy and Physiology, 11e 19 Right Atrium Receives blood from 3 sources superior vena cava, inferior vena cava and coronary sinus Interatrial septum partitions the atria Fossa ovalis is a remnant of the fetal foramen ovale Tricuspid valve Blood flows through into right ventricle has three cusps composed of dense CT covered by endocardium

20. Principles of Human Anatomy and Physiology, 11e 20 Right Ventricle Forms most of anterior surface of heart Papillary muscles are cone shaped trabeculae carneae (raised bundles of cardiac muscle) Chordae tendineae: cords between valve cusps and papillary muscles Interventricular septum: partitions ventricles Pulmonary semilunar valve: blood flows into pulmonary trunk

21. Principles of Human Anatomy and Physiology, 11e 21 Left Atrium Forms most of the base of the heart Receives blood from lungs - 4 pulmonary veins (2 right + 2 left) Bicuspid valve: blood passes through into left ventricle has two cusps to remember names of this valve, try the pneumonic LAMB Left Atrioventricular, Mitral, or Bicuspid valve

22. Principles of Human Anatomy and Physiology, 11e 22 Left Ventricle Forms the apex of heart Chordae tendineae anchor bicuspid valve to papillary muscles (also has trabeculae carneae like right ventricle) Aortic semilunar valve: blood passes through valve into the ascending aorta just above valve are the openings to the coronary arteries

23. Principles of Human Anatomy and Physiology, 11e 23 Myocardial Thickness and Function The thickness of the myocardium of the four chambers varies according to the function of each chamber. The atria walls are thin because they deliver blood to the ventricles. The ventricle walls are thicker because they pump blood greater distances (Figure 20.4a). The right ventricle walls are thinner than the left because they pump blood into the lungs, which are nearby and offer very little resistance to blood flow. The left ventricle walls are thicker because they pump blood through the body where the resistance to blood flow is greater.

24. Principles of Human Anatomy and Physiology, 11e 24 Myocardial Thickness and Function Thickness of myocardium varies according to the function of the chamber Atria are thin walled, deliver blood to adjacent ventricles

25. Principles of Human Anatomy and Physiology, 11e 25 Thickness of Cardiac Walls

26. Principles of Human Anatomy and Physiology, 11e 26 HEART VALVES AND CIRCULATION OF BLOOD Valves open and close in response to pressure changes as the heart contracts and relaxes.

27. Principles of Human Anatomy and Physiology, 11e 27 Fibrous Skeleton of Heart (Figure 20.5). Dense CT rings surround the valves of the heart, fuse and merge with the interventricular septum Support structure for heart valves Insertion point for cardiac muscle bundles Electrical insulator between atria and ventricles prevents direct propagation of AP�s to ventricles

28. Principles of Human Anatomy and Physiology, 11e 28 A-V valves open and allow blood to flow from atria into ventricles when ventricular pressure is lower than atrial pressure occurs when ventricles are relaxed, chordae tendineae are slack and papillary muscles are relaxed Atrioventricular Valves Open

29. Principles of Human Anatomy and Physiology, 11e 29 A-V valves close preventing backflow of blood into atria occurs when ventricles contract, pushing valve cusps closed, chordae tendinae are pulled taut and papillary muscles contract to pull cords and prevent cusps from everting Atrioventricular Valves Close

30. Principles of Human Anatomy and Physiology, 11e 30 Semilunar Valves SL valves open with ventricular contraction allow blood to flow into pulmonary trunk and aorta SL valves close with ventricular relaxation prevents blood from returning to ventricles, blood fills valve cusps, tightly closing the SL valves

31. Principles of Human Anatomy and Physiology, 11e 31 Heart valve disorders Stenosis is a narrowing of a heart valve which restricts blood flow. Insufficiency or incompetence is a failure of a valve to close completely. Stenosed valves may be repaired by balloon valvuloplasty, surgical repair, or valve replacement.

32. Principles of Human Anatomy and Physiology, 11e 32 Valve Function Review

33. Principles of Human Anatomy and Physiology, 11e 33 Valve Function Review

34. Principles of Human Anatomy and Physiology, 11e 34 Two closed circuits, the systemic and pulmonic Systemic circulation left side of heart pumps blood through body left ventricle pumps oxygenated blood into aorta aorta branches into many arteries that travel to organs arteries branch into many arterioles in tissue arterioles branch into thin-walled capillaries for exchange of gases and nutrients deoxygenated blood begins its return in venules venules merge into veins and return to right atrium Blood Circulation

35. Principles of Human Anatomy and Physiology, 11e 35 Pulmonary circulation right side of heart pumps deoxygenated blood to lungs right ventricle pumps blood to pulmonary trunk pulmonary trunk branches into pulmonary arteries pulmonary arteries carry blood to lungs for exchange of gases oxygenated blood returns to heart in pulmonary veins Blood Circulation (cont.)

36. Principles of Human Anatomy and Physiology, 11e 36 Blood Circulation Blood flow blue = deoxygenated red = oxygenated

37. Principles of Human Anatomy and Physiology, 11e 37 Coronary Circulation The flow of blood through the many vessels that flow through the myocardium of the heart is called the coronary (cardiac) circulation; it delivers oxygenated blood and nutrients to and removes carbon dioxide and wastes from the myocardium (Figure 20.8b). When blockage of a coronary artery deprives the heart muscle of oxygen, reperfusion may damage the tissue further. This damage is due to free radicals. Drugs that lessen reperfusion damage after a heart attack are being developed .

38. Principles of Human Anatomy and Physiology, 11e 38 Coronary Circulation Coronary circulation is blood supply to the heart Heart as a very active muscle needs lots of O2 When the heart relaxes high pressure of blood in aorta pushes blood into coronary vessels Many anastomoses connections between arteries supplying blood to the same region, provide alternate routes if one artery becomes occluded

39. Principles of Human Anatomy and Physiology, 11e 39 Coronary Arteries Branches off aorta above aortic semilunar valve Left coronary artery circumflex branch in coronary sulcus, supplies left atrium and left ventricle anterior interventricular art. supplies both ventricles Right coronary artery marginal branch in coronary sulcus, supplies right ventricle posterior interventricular art. supplies both ventricles

40. Principles of Human Anatomy and Physiology, 11e 40 Coronary Veins Collects wastes from cardiac muscle Drains into a large sinus on posterior surface of heart called the coronary sinus Coronary sinus empties into right atrium

41. Principles of Human Anatomy and Physiology, 11e 41 CARDIAC MUSCLE AND THE CARDIAC CONDUCTION SYSTEM

42. Principles of Human Anatomy and Physiology, 11e 42 Histology of Cardiac Muscle Compared to skeletal muscle fibers, cardiac muscle fibers are shorter in length, larger in diameter, and squarish rather than circular in transverse section (Figure 20.9). They also exhibit branching (Table 4.4B). Fibers within the networks are connected by intercalated discs, which consist of desmosomes and gap junctions Cardiac muscles have the same arrangement of actin and myosin, and the same bands, zones, and Z discs as skeletal muscles. They do have less sarcoplasmic reticulum than skeletal muscles and require Ca+2 from extracellular fluid for contraction.

43. Principles of Human Anatomy and Physiology, 11e 43 Cardiac Muscle Histology Branching, intercalated discs with gap junctions, involuntary, striated, single central nucleus per cell

44. Principles of Human Anatomy and Physiology, 11e 44 Cardiac Myofibril

45. Principles of Human Anatomy and Physiology, 11e 45 Conduction System of Heart

46. Principles of Human Anatomy and Physiology, 11e 46 Myocardial ischemia and infarction Reduced blood flow through coronary arteris may cause ischemia. Ischemia cuases hypoxia and may weaken the myocardial cells. Ischemia is often manifested through angina pectoris. A complete obstruction of flow in a coronary artery may cause myocardial infarction (heart attack). Tissue distal to the obstruction dies and is replaced by scar tissur. Treatment may involve injection of thrombolytic agents, coronary angioplasty, or coronary artery bypass grafts. While it was long thought that cardiac muscle lacked stem cells, recent studies five evidence for replacement of heart cells. It appears that stem cells in the blood can migrate to the heart and differentiate into myocardial cells.

47. Principles of Human Anatomy and Physiology, 11e 47 Autorhythmic Cells: The Conduction System Cardiac muscle cells are autorhythmic cells because they are self-excitable. They repeatedly generate spontaneous action potentials that then trigger heart contractions. These cells act as a pacemaker to set the rhythm for the entire heart. They form the conduction system, the route for propagating action potential through the heart muscle.

48. Principles of Human Anatomy and Physiology, 11e 48 Conduction System of Heart

49. Principles of Human Anatomy and Physiology, 11e 49 Conduction Components of this system are the sinoartrial (SA) node (pacemaker), atrioventricular (AV) node, atrioventricular bundle (bundle of His), right and left bundle branches, and the conduction myofibers (Purkinje fibers) (Figure 20.10) Signals from the autonomic nervous system and hormones, such as epinephrine, do modify the heartbeat (in terms of rate and strength of contraction), but they do not establish the fundamental rhythm.

50. Principles of Human Anatomy and Physiology, 11e 50 Autorhythmic Cells Cells fire spontaneously, act as pacemaker and form conduction system for the heart SA node cluster of cells in wall of Rt. Atria begins heart activity that spreads to both atria excitation spreads to AV node AV node in atrial septum, transmits signal to bundle of His AV bundle of His the connection between atria and ventricles divides into bundle branches & purkinje fibers, large diameter fibers that conduct signals quickly Conduction System of Heart

51. Principles of Human Anatomy and Physiology, 11e 51 Rhythm of Conduction System SA node fires spontaneously 90-100 times per minute AV node fires at 40-50 times per minute If both nodes are suppressed fibers in ventricles by themselves fire only 20-40 times per minute Artificial pacemaker needed if pace is too slow Extra beats forming at other sites are called ectopic pacemakers caffeine & nicotine increase activity

52. Principles of Human Anatomy and Physiology, 11e 52 Timing of Atrial & Ventricular Excitation SA node setting pace since is the fastest In 50 msec excitation spreads through both atria and down to AV node 100 msec delay at AV node due to smaller diameter fibers- allows atria to fully contract filling ventricles before ventricles contract In 50 msec excitation spreads through both ventricles simultaneously

53. Principles of Human Anatomy and Physiology, 11e 53 Abnormal Conduction Sick sinus syndrome describes an abnormally functioning SA node that initiates irregular heart beats. When abnormal pacing of the heart develops, heart rhythm can be restored by implanting an artificail pacemaker, a device that sends out small, regular currents to stimulate myocardial contraction..

54. Principles of Human Anatomy and Physiology, 11e 54 Action potential and contraction of contractile fibers An impulse in a ventricular contractile fiber is characterized by rapid depolarization, plateau, and repolarization (Figure 20.11). The refractory period of a cardiac muscle fiber (the time interval when a second contraction cannot be triggered) is longer than the contraction itself (Figure 20.11). Therefore tetanus cannot occur in myocardial cells.

55. Principles of Human Anatomy and Physiology, 11e 55 Conduction System of the Heart

56. Principles of Human Anatomy and Physiology, 11e 56 Physiology of Contraction Depolarization, plateau, repolarization

57. Principles of Human Anatomy and Physiology, 11e 57 Depolarization & Repolarization Depolarization Cardiac cell resting membrane potential is -90mv excitation spreads through gap junctions fast Na+ channels open for rapid depolarization Plateau phase 250 msec (only 1msec in neuron) slow Ca+2 channels open, let Ca +2 enter from outside cell and from storage in sarcoplasmic reticulum, while K+ channels close Ca +2 binds to troponin to allow for actin-myosin cross-bridge formation & tension development Repolarization Ca+2 channels close and K+ channels open & -90mv is restored as potassium leaves the cell Refractory period very long so heart can fill

58. Principles of Human Anatomy and Physiology, 11e 58 Action Potential in Cardiac Muscle

59. Principles of Human Anatomy and Physiology, 11e 59 ATP production in cardiac muscle Cardiac muscle relies on aerobic cellular respiration for ATP production. Cardiac muscle also produces some ATP from creatine phosphate The presence of creatine kinase (CK) in the blood indicates injury of cardiac muscle usually caused by a myocardial infarction.

60. Principles of Human Anatomy and Physiology, 11e 60 Electrocardiogram Impulse conduction through the heart generates electrical currents that can be detected at the surface of the body. A recording of the electrical changes that accompany each cardiac cycle (heartbeat) is called an electrocardiogram (ECG or EKG). The ECG helps to determine if the conduction pathway is abnormal, if the heart is enlarged, and if certain regions are damaged. Figure 20.12 shows a typical ECG.

61. Principles of Human Anatomy and Physiology, 11e 61 Electrocardiogram---ECG or EKG EKG Action potentials of all active cells can be detected and recorded P wave atrial depolarization P to Q interval conduction time from atrial to ventricular excitation QRS complex ventricular depolarization T wave ventricular repolarization

62. Principles of Human Anatomy and Physiology, 11e 62

63. Principles of Human Anatomy and Physiology, 11e 63 ECG In a typical Lead II record, three clearly visible waves accompany each heartbeat It consists of:. P wave (atrial depolarization - spread of impulse from SA node over atria) QRS complex (ventricular depolarization - spread of impulse through ventricles) T wave (ventricular repolarization). Correlation of ECG waves with atrial and ventricular systole (Figure 20.13)

64. Principles of Human Anatomy and Physiology, 11e 64 ECG As atrial fibers depolarize, the P wave appears. After the P wave begins, the atria contract (atrial systole). Action potential slows at the AV node giving the atria time to contract. The action potential moves rapidly through the bundle branches, Purkinje fibers, and the ventricular myocardium producing the QRS complex. Ventricular contraction after the QRS comples and continues through the ST segment. Repolarization of the ventricles produces the T wave. Both atria and ventricles repolarize and the P wave appears.

65. Principles of Human Anatomy and Physiology, 11e 65 THE CARDIAC CYCLE A cardiac cycle consists of the systole (contraction) and diastole (relaxation) of both atria, rapidly followed by the systole and diastole of both ventricles. Pressure and volume changes during the cardiac cycle During a cardiac cycle atria and ventricles alternately contract and relax forcing blood from areas of high pressure to areas of lower pressure. Figure 20.14 shows the relation between the ECG and changes in atrial pressure, ventricular pressure, aortic pressure, and ventricular volume during the cardia cycle.

66. Principles of Human Anatomy and Physiology, 11e 66 One Cardiac Cycle - Vocabulary At 75 beats/min, one cycle requires 0.8 sec. systole (contraction) and diastole (relaxation) of both atria, plus the systole and diastole of both ventricles End diastolic volume (EDV) volume in ventricle at end of diastole, about 130ml End systolic volume (ESV) volume in ventricle at end of systole, about 60ml Stroke volume (SV) the volume ejected per beat from each ventricle, about 70ml SV = EDV - ESV

67. Principles of Human Anatomy and Physiology, 11e 67 Phases of Cardiac Cycle Isovolumetric relaxation brief period when volume in ventricles does not change--as ventricles relax, pressure drops and AV valves open Ventricular filling rapid ventricular filling:as blood flows from full atria diastasis: as blood flows from atria in smaller volume atrial systole pushes final 20-25 ml blood into ventricle Ventricular systole ventricular systole isovolumetric contraction brief period, AV valves close before SL valves open ventricular ejection: as SL valves open and blood is ejected

68. Principles of Human Anatomy and Physiology, 11e 68 Cardiac Cycle

69. Principles of Human Anatomy and Physiology, 11e 69 Atrial systole/ventricular diastole The atria contract, increasing pressure forces the AV valves to open. The amount of blood in the ventricle at the end of diastole is the End Diastolic Volume (EDV) Ventricular systole/atrial diastole Ventricles contract and increasing pressure forces the AV valves to close. AV and SL valves are all closed (isovolumetric contraction). Pressure continues to rise opening the SL valves leading to ventricular ejection. The amount of blood in the left ventrical at the end of systole is End Systolic Volume (ESV). Stroke volume (SV) is the volume of blood ejected from the left ventricle SV = EDV-ESV.

70. Principles of Human Anatomy and Physiology, 11e 70 Relaxation period Both atria and ventricles are relaxed. Pressure in the ventricles fall and the SL valves close. Brief time all four valves are closed is the isovolumetric relaxation. Pressure in the ventricles continues to fall, the AV valves open, and ventricular filling begins.

71. Principles of Human Anatomy and Physiology, 11e 71 Ventricular Pressures Blood pressure in aorta is 120mm Hg Blood pressure in pulmonary trunk is 30mm Hg Differences in ventricle wall thickness allows heart to push the same amount of blood with more force from the left ventricle The volume of blood ejected from each ventricle is 70ml (stroke volume) Why do both stroke volumes need to be same?

72. Principles of Human Anatomy and Physiology, 11e 72 Auscultation The act of listening to sounds within the body is called auscultation, and it is usually done with a stethoscope. The sound of a heartbeat comes primarily from the turbulence in blood flow caused by the closure of the valves, not from the contraction of the heart muscle (Figure 20.15). The first heart sound (lubb) is created by blood turbulence associated with the closing of the atrioventricular valves soon after ventricular systole begins. The second heart sound (dupp) represents the closing of the semilunar valves close to the end of the ventricular systole.

73. Principles of Human Anatomy and Physiology, 11e 73 Heart Sounds

74. Principles of Human Anatomy and Physiology, 11e 74 Murmurs A heart murmur is an abnormal sound that consists of a flow noise that is heard before, between, or after the lubb-dupp or that may mask the normal sounds entirely. Some murmurs are caused by turbulent blood flow around valves due to abnormal anatomy or increased volume of flow. Not all murmurs are abnormal or symptomatic, but most indicate a valve disorder.

75. Principles of Human Anatomy and Physiology, 11e 75 CARDIAC OUTPUT Since the body�s need for oxygen varies with the level of activity, the heart�s ability to discharge oxygen-carrying blood must also be variable. Body cells need specific amounts of blood each minute to maintain health and life. Cardiac output (CO) is the volume of blood ejected from the left ventricle (or the right ventricle) into the aorta (or pulmonary trunk) each minute. Cardiac output equals the stroke volume, the volume of blood ejected by the ventricle with each contraction, multiplied by the heart rate, the number of beats per minute. CO = SV X HR Cardiac reserve is the ratio between the maximum cardiac output a person can achieve and the cardiac output at rest.

76. Principles of Human Anatomy and Physiology, 11e 76 Cardiac Output CO = SV x HR at 70ml stroke volume & 75 beat/min----5 and 1/4 liters/min entire blood supply passes through circulatory system every minute Cardiac reserve is maximum output/output at rest average is 4-5x while athlete�s is 7-8x

77. Principles of Human Anatomy and Physiology, 11e 77 Influences on Stroke Volume Preload (affect of stretching) Frank-Starling Law of Heart more muscle is stretched, greater force of contraction more blood more force of contraction results Contractility autonomic nerves, hormones, Ca+2 or K+ levels Afterload amount of pressure created by the blood in the way high blood pressure creates high afterload

78. Principles of Human Anatomy and Physiology, 11e 78 Stroke Volume and Heart Rate

79. Principles of Human Anatomy and Physiology, 11e 79 Preload: Effect of Stretching According to the Frank-Starling law of the heart, a greater preload (stretch) on cardiac muscle fibers just before they contract increases their force of contraction during systole. Preload is proportional to EDV. EDV is determined by length of ventricular diastole and venous return. The Frank-Starling law of the heart equalizes the output of the right and left ventricles and keeps the same volume of blood flowing to both the systemic and pulmonary circulations.

80. Principles of Human Anatomy and Physiology, 11e 80 Contractility Myocardial contractility, the strength of contraction at any given preload, is affected by positive and negative inotropic agents. Positive inotropic agents increase contractility Negative inotropic agents decrease contractility. For a constant preload, the stroke volume increases when positive inotropic agents are present and decreases when negative inotropic agents are present.

81. Principles of Human Anatomy and Physiology, 11e 81 Afterload The pressure that must be overcome before a semilunar valve can open is the afterload. In congestive heart failure, blood begins to remain in the ventricles increasing the preload and ultimately causing an overstretching of the heart and less forceful contraction Left ventricular failure results in pulmonary edema Right ventricular failure results in peripheral edema.

82. Principles of Human Anatomy and Physiology, 11e 82 Regulation of Heart Rate Cardiac output depends on heart rate as well as stroke volume. Changing heart rate is the body�s principal mechanism of short-term control over cardiac output and blood pressure. Several factors contribute to regulation of heart rate.

83. Principles of Human Anatomy and Physiology, 11e 83 Regulation of Heart Rate Nervous control from the cardiovascular center in the medulla Sympathetic impulses increase heart rate and force of contraction parasympathetic impulses decrease heart rate. Baroreceptors (pressure receptors) detect change in BP and send info to the cardiovascular center located in the arch of the aorta and carotid arteries Heart rate is also affected by hormones epinephrine, norepinephrine, thyroid hormones ions (Na+, K+, Ca2+) age, gender, physical fitness, and temperature

84. Principles of Human Anatomy and Physiology, 11e 84 Regulation of Heart Rate

85. Principles of Human Anatomy and Physiology, 11e 85 Autonomic regulation of the heart Nervous control of the cardiovascular system stems from the cardiovascular center in the medulla oblongata (Figure 20.16). Proprioceptors, baroreceptors, and chemoreceptors monitor factors that influence the heart rate. Sympathetic impulses increase heart rate and force of contraction; parasympathetic impulses decrease heart rate.

86. Principles of Human Anatomy and Physiology, 11e 86 Chemical regulation of heart rate Heart rate affected by hormones (epinephrine, norepinephrine, thyroid hormones). Cations (Na+, K+, Ca+2) also affect heart rate. Other factors such as age, gender, physical fitness, and temperature also affect heart rate. Figure 20.16 summarizes the factors that can increase stoke volume and heart rate to cause an increase in cardiac output..

87. Principles of Human Anatomy and Physiology, 11e 87 Risk Factors for Heart Disease Risk factors in heart disease: high blood cholesterol level high blood pressure cigarette smoking obesity & lack of regular exercise. Other factors include: diabetes mellitus genetic predisposition male gender high blood levels of fibrinogen left ventricular hypertrophy

88. Principles of Human Anatomy and Physiology, 11e 88 Plasma Lipids and Heart Disease Risk factor for developing heart disease is high blood cholesterol level. promotes growth of fatty plaques Most lipids are transported as lipoproteins low-density lipoproteins (LDLs) high-density lipoproteins (HDLs) very low-density lipoproteins (VLDLs) HDLs remove excess cholesterol from circulation LDLs are associated with the formation of fatty plaques VLDLs contribute to increased fatty plaque formation There are two sources of cholesterol in the body: in foods we ingest & formed by liver

89. Principles of Human Anatomy and Physiology, 11e 89 Desirable Levels of Blood Cholesterol for Adults TC (total cholesterol) under 200 mg/dl LDL under 130 mg/dl HDL over 40 mg/dl Normally, triglycerides are in the range of 10-190 mg/dl. Among the therapies used to reduce blood cholesterol level are exercise, diet, and drugs.

90. Principles of Human Anatomy and Physiology, 11e 90 EXERCISE AND THE HEART A person�s cardiovascular fitness can be improved with regular exercise. Aerobic exercise (any activity that works large body muscles for at least 20 minutes, preferably 3 � 5 times per week) increases cardiac output and elevates metabolic rate. Several weeks of training results in maximal cardiac output and oxygen delivery to tissues Regular exercise also decreases anxiety and depression, controls weight, and increases fibrinolytic activity. Sustained exercise increases oxygen demand in muscles As a heart fails, a person�s mobility decreases. Heart transplants may help such individuals. Other possibilities include cardiac assist devices and surgical procedures. Table 20.1 describes several devices and procedures.

91. Principles of Human Anatomy and Physiology, 11e 91 DEVELOPMENT OF THE HEART The heart develops from mesoderm before the end of the third week of gestation. The endothelial tubes develop into the four-chambered heart and great vessels of the heart (Figure 20.18).

92. Principles of Human Anatomy and Physiology, 11e 92 Developmental Anatomy of the Heart The heart develops from mesoderm before the end of the third week of gestation. The tubes develop into the four-chambered heart and great vessels of the heart.

93. Principles of Human Anatomy and Physiology, 11e 93 DISORDERS: HOMEOSTATIC IMBALANCES

94. Principles of Human Anatomy and Physiology, 11e 94 Clinical Problems MI = myocardial infarction death of area of heart muscle from lack of O2 replaced with scar tissue results depend on size & location of damage Blood clot use clot dissolving drugs streptokinase or t-PA & heparin balloon angioplasty Angina pectoris----heart pain from ischemia of cardiac muscle

95. Principles of Human Anatomy and Physiology, 11e 95 CAD Coronary artery disease (CAD), or coronary heart disease (CHD), is a condition in which the heart muscle receives an inadequate amount of blood due to obstruction of its blood supply. It is the leading cause of death in the United States each year. The principal causes of obstruction include atherosclerosis, coronary artery spasm, or a clot in a coronary artery. Risk factors for development of CAD include high blood cholesterol levels, high blood pressure, cigarette smoking, obesity, diabetes, �type A� personality, and sedentary lifestyle.

96. Principles of Human Anatomy and Physiology, 11e 96 CAD Atherosclerosis is a process in which smooth muscle cells proliferate and fatty substances, especially cholesterol and triglycerides (neutral fats), accumulate in the walls of the medium-sized and large arteries in response to certain stimuli, such as endothelial damage (Figure 20.18). Diagnosis of CAD includes such procedures as cardiac catherization and cardiac angiography. Treatment options for CAD include drugs and coronary artery bypass grafting (Figure 20.19).

97. Principles of Human Anatomy and Physiology, 11e 97 Coronary Artery Disease Heart muscle receiving insufficient blood supply narrowing of vessels---atherosclerosis, artery spasm or clot atherosclerosis--smooth muscle & fatty deposits in walls of arteries Treatment drugs, bypass graft, angioplasty, stent

98. Principles of Human Anatomy and Physiology, 11e 98 By-pass Graft

99. Principles of Human Anatomy and Physiology, 11e 99 Percutaneous Transluminal Coronary Angioplasty Stent

100. Principles of Human Anatomy and Physiology, 11e 100 Congenital Heart Defects A congenital defect is a defect that exists at birth, and usually before birth. Congenital defects of the heart include coarctation of the aorta, patent ductus arteriosus, septal defects (interatrial or interventricular), valvular stenosis, and tetralogy of Fallot. Some congenital defects are not serious or remain asymptomatic; others heal themselves. A few congenital defects are life threatening and must be corrected surgically. Fortunately, surgical techniques are highly refined for most of the defects listed.

101. Principles of Human Anatomy and Physiology, 11e 101 Arrythmia Arrhythmia (disrhythmia) is an irregularity in heart rhythm resulting from a defect in the conduction system of the heart. Categories are bradycardia, tachycardia, and fibrillation. Those that begin in the atria are supraventricular or atrial. Those that begin in the ventricle are ventricular.

102. Principles of Human Anatomy and Physiology, 11e 102 Congestive Heart Failure Congestive heart failure is a chronic or acute state that results when the heart is not capable of supplying the oxygen demands of the body. Causes of CHF coronary artery disease, hypertension, MI, valve disorders, congenital defects Left side heart failure less effective pump so more blood remains in ventricle heart is overstretched & even more blood remains blood backs up into lungs as pulmonary edema suffocation & lack of oxygen to the tissues Right side failure fluid builds up in tissues as peripheral edema

103. Principles of Human Anatomy and Physiology, 11e 103 end