Course: Health Sciences – Anatomy and Physiology —————————————————

Course: Health Sciences – Anatomy and Physiology ——————————————————————————————————————— Resources: Text Book: Anatomy and Physiology: An Integrated Approach; McKinley, O’Loughlin, and Bidle; fourth edition, McGraw-Hill, 2019. (ISBN: 978-1-260-26521-7) Chapter 18: Cardiovascular System: Blood Chapter 19: Cardiovascular System: Heart Chapter 20: Cardiovascular System: Vessels and Circulation Chapter 21: Lymphatic System Chapter 22: Immune System and the Body’s Defense —————————————————————————————————– Module Objective (MO) 3.1: Understand and explain concepts on topics from Chapter 3: Cardiovascular System, such as heart anatomy heart physiology blood flow through heart cardiac cycle electrical conductance heart sounds homeostatic imbalances (diseases & disorders) —————————————————————————————————————– MO 3.2: Understand and explain concepts on topics from Chapter 4: Blood Vessels, such as differences between arteries, veins, and capillaries angiogenesis atherosclerosis edema local blood flow distribution of blood in body/circulation blood pressure pulse/pressure points blood pressure homeostatic imbalances blood flow distribution during exercise ————————————————————————————————————- MO 3.3: Understand and explain concepts on topics from Chapter 16: Lymphatic System and Immunity, such as the three lines of defense and what comprises each the cells of the innate immune system the cells of the adaptive immune system the organs of the lymphatic system lymph flow origins of B and T cells differences between primary and secondary immune responses the different types of acquired immunities the over/under reactions of the immune system (example: allergic reactions) autoimmunity lifespan changes ————————————————————————————————————- Chapter – Cardiovascular System – Details Page of 87 Zoom Cardiovascular System https://youtu.be/RZrkbD6cneU 1 2 Introduction • The heart pumps 7,000 liters of blood through the body each day • The heart contracts 2.5 billion times in an average lifetime • The heart and all blood vessels make up the cardiovascular system • The blood vessels make up two circuits: • Pulmonary circuit • Systemic circuit © 2013 Pearson Education, Inc. The Pulmonary and Systemic Circuits • Heart is transport system; two side-by-side pumps – Right side receives oxygen-poor blood from tissues • Pumps to lungs to get rid of CO2, pick up O2, via pulmonary circuit – Left side receives oxygenated blood from lungs • Pumps to body tissues via systemic circuit © 2013 Pearson Education, Inc. The Pulmonary and Systemic Circuits • Receiving chambers of heart: – Right atrium • Receives blood returning from systemic circuit – Left atrium • Receives blood returning from pulmonary circuit © 2013 Pearson Education, Inc. The Pulmonary and Systemic Circuits • Pumping chambers of heart: – Right ventricle • Pumps blood through pulmonary circuit – Left ventricle • Pumps blood through systemic circuit • Three Types of Blood Vessels 1. Arteries • Carry blood away from heart 2. Veins • Carry blood to heart 3. Capillaries • Networks between arteries and veins • Capillaries – Also called exchange vessels – Exchange materials between blood and tissues – Materials include dissolved gases, nutrients, waste products 8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alveolus Oxygenated blood Deoxygenated blood CO2 CO2 CO2 CO2 CO2 CO2 O2 O2 O2 O2 O2 O2 O2 O2 CO2 CO2 Right atrium Right ventricle Left atrium Left ventricle Systemic circuit delivers oxygen to all body cells and carries away wastes. Oxygenated blood pumped to all body tissues via aorta Deoxygenated blood pumped to lungs via pulmonary arteries Pulmonary circuit eliminates carbon dioxide via the lungs and oxygenates the blood. Oxygenated blood returns to heart via pulmonary veins Deoxygenated blood returns to heart via venae cavae • Four Chambers of the Heart 1. Right atrium • Collects blood from systemic circuit 2. Right ventricle • Pumps blood to pulmonary circuit 3. Left atrium • Collects blood from pulmonary circuit 4. Left ventricle • Pumps blood to systemic circuit 10 Structure of the Heart • The heart is a hollow, cone-shaped, muscular pump • There are four chambers: • Two atria (for blood storage) • Two ventricles (one low pressure pump and one high pressure pump) 11 Size and Location of the Heart Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 0 1 2 3 4 5 cm © McGraw-Hill Companies, Inc./Photo and dissection by Christine Eckel • The heart size varies with body size • The heart lies in the thoracic cavity • The average size of the heart is: • 14 cm long (5.5 inches) • 9 cm wide (3.5 inches) • The heart is: • Posterior to the sternum • Medial to the lungs • Anterior to the vertebral column • The base lies beneath the 2nd rib • The apex at the 5th intercostal space • It lays just above the diaphragm 12 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Diaphragm Base of heart Apex (tip) of heart Heart Sternum 13 Wall of the Heart Endocardium Myocardium Epicardium (visceral pericardium) Pericardial cavity Parietal pericardium Fibrous pericardium Coronary blood vessel • The heart wall has three distinct layers: • Epicardium (outer layer) (protective covering) • Myocardium (middle layer) (contracts to pump blood from heart chambers) • Endocardium (inner layer) (protective lining for chambers and valves) Anatomy of the Heart • The Pericardium – Pericardial cavity • Is between parietal and visceral layers • Contains pericardial fluid – Pericardial sac • Fibrous tissue • Surrounds and stabilizes heart The Location of the Heart in the Thoracic Cavity Wrist (corresponds to base of heart) Inner wall (corresponds to epicardium) Air space (corresponds to pericardial cavity) Outer wall (corresponds to parietal pericardium) Balloon Cut edge of parietal pericardium Fibrous tissue of pericardial sac Parietal pericardium Areolar tissue Mesothelium Cut edge of epicardium Apex of heart Base of heart Fibrous attachment to diaphragm The relationship between the heart and the pericardial cavity; compare with the fist-and-balloon example. © 2013 Pearson Education, Inc. Homeostatic Imbalance • Pericarditis – Inflammation of pericardium – Roughens membrane surfaces à pericardial friction rub (creaking sound) heard with stethoscope – Cardiac tamponade • Excess fluid sometimes compresses heart à limited pumping ability 17 Heart Chambers and Valves • The heart is divided into four chambers: • Right atrium: • Receives blood from the: • Inferior vena cava • Superior vena cava • Coronary sinus (collection of veins in the myocardium) • Right ventricle • Receives blood from the right atrium • Left atrium • Receives blood from the pulmonary veins • Left ventricle • Receives blood from the left atrium © 2013 Pearson Education, Inc. Heart Valves • Ensure unidirectional blood flow through heart • Open and close in response to pressure changes • Two atrioventricular (AV) valves – Prevent backflow into atria when ventricles contract – Tricuspid valve (right AV valve) – Mitral valve (left AV valve, bicuspid valve) – Chordae tendineae anchor cusps to papillary muscles • Hold valve flaps in closed position © 2013 Pearson Education, Inc. 1 2 3 Blood returning to the heart fills atria, pressing against the AV valves. The increased pressure forces AV valves open. As ventricles fill, AV valve flaps hang limply into ventricles. 1 2 3 Atria contract, forcing additional blood into ventricles. Ventricles contract, forcing blood against AV valve cusps. AV valves close. Papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria. AV valves open; atrial pressure greater than ventricular pressure AV valves closed; atrial pressure less than ventricular pressure Direction of blood flow Cusp of atrioventricular valve (open) Atrium Chordae tendineae Papillary muscle Atrium Cusps of atrioventricular valve (closed) Blood in ventricle Ventricle Figure 18.7 The atrioventricular (AV) valves. © 2013 Pearson Education, Inc. Heart Valves • Two semilunar (SL) valves – Prevent backflow into ventricles when ventricles relax – Open and close in response to pressure changes – Aortic semilunar valve – Pulmonary semilunar valve © 2013 Pearson Education, Inc. As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open. As ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close. Aorta Pulmonary trunk Semilunar valves open Semilunar valves closed Figure 18.8 The semilunar (SL) valves. 22 Fibrous skeleton Mitral valve Posterior Opening of left coronary artery Aortic valve Tricuspid valve Pulmonary valve 22 • The fibrous rings, together with other masses of dense connective tissue in the portion of the septum between the ventricles (interventricular septum), constitute the skeleton of the heart © 2013 Pearson Education, Inc. Homeostatic Imbalance • Two conditions severely weaken heart: – Incompetent valve • Blood backflows so heart repumps same blood over and over – Valvular stenosis • Stiff flaps – constrict opening à heart must exert more force to pump blood • Valve replaced with mechanical, animal, or cadaver valve © 2013 Pearson Education, Inc. Atria: The Receiving Chambers • Small, thin-walled • Contribute little to propulsion of blood • Three veins empty into right atrium: – Superior vena cava, inferior vena cava, coronary sinus • Four pulmonary veins empty into left atrium © 2013 Pearson Education, Inc. Ventricles: The Discharging Chambers • Thicker walls than atria • Actual pumps of heart • Right ventricle – Pumps blood into pulmonary trunk • Left ventricle – Pumps blood into aorta (largest artery in body) © 2013 Pearson Education, Inc. Figure 18.5e Gross anatomy of the heart. Superior vena cava Right pulmonary artery Pulmonary trunk Right atrium Right pulmonary veins Fossa ovalis Pectinate muscles Tricuspid valve Right ventricle Chordae tendineae Trabeculae carneae Inferior vena cava Aorta Left pulmonary artery Left atrium Left pulmonary veins Mitral (bicuspid) valve Aortic valve Pulmonary valve Left ventricle Papillary muscle Interventricular septum Epicardium Myocardium Endocardium Frontal section © 2013 Pearson Education, Inc. Oxygen-poor blood Oxygen-rich blood Superior vena cava (SVC) Inferior vena cava (IVC) Coronary sinus SVC IVC Coronary sinus Slide 2Figure 18.9 The heart is a double pump, each side supplying its own circuit. STOP © 2013 Pearson Education, Inc. Slide 3Figure 18.9 The heart is a double pump, each side supplying its own circuit. Oxygen-poor blood Oxygen-rich blood Superior vena cava (SVC) Inferior vena cava (IVC) Coronary sinus Right atrium SVC IVC Coronary sinus Right atrium © 2013 Pearson Education, Inc. Figure 18.9 The heart is a double pump, each side supplying its own circuit. Slide 4 Oxygen-poor blood Oxygen-rich blood Superior vena cava (SVC) Inferior vena cava (IVC) Coronary sinus Right atrium Tricuspid valve Right ventricle SVC IVC Coronary sinus Right atrium Tricuspid valve Right ventricle © 2013 Pearson Education, Inc. Figure 18.9 The heart is a double pump, each side supplying its own circuit. Slide 5 Oxygen-poor blood Oxygen-rich blood Superior vena cava (SVC) Inferior vena cava (IVC) Coronary sinus Right atrium Tricuspid valve Pulmonary Semilunar valveRight ventricle Pulmonary trunk SVC IVC Coronary sinus Right atrium Tricuspid valve Right ventricle Pulmonary arteries Pulmonary trunk Pulmonary semilunar valve © 2013 Pearson Education, Inc. Figure 18.9 The heart is a double pump, each side supplying its own circuit. Slide 6 Oxygen-poor blood Oxygen-rich blood Superior vena cava (SVC) Inferior vena cava (IVC) Coronary sinus Right atrium Tricuspid valve Pulmonary Semilunar valveRight ventricle Pulmonary trunk SVC IVC Coronary sinus Right atrium Tricuspid valve Right ventricle Pulmonary arteries Pulmonary trunk Pulmonary semilunar valve Oxygen-poor blood is carried in two pulmonary arteries to the lungs (pulmonary circuit) to be oxygenated. To lungs Pulmonary capillaries © 2013 Pearson Education, Inc. Oxygen-poor blood Oxygen-rich blood Pulmonary veins Four pulmonary veins Slide 7Figure 18.9 The heart is a double pump, each side supplying its own circuit. © 2013 Pearson Education, Inc. Figure 18.9 The heart is a double pump, each side supplying its own circuit. Slide 8 Pulmonary veins Left atrium Left atrium Four pulmonary veins Blood Flow Through the Heart Oxygen-poor blood Oxygen-rich blood Right ventricle © 2013 Pearson Education, Inc. Figure 18.9 The heart is a double pump, each side supplying its own circuit. Slide 9 Oxygen-poor blood Oxygen-rich blood Pulmonary veins Left atrium Mitral valve Left ventricle Mitral valveLeft ventricle Left atrium Four pulmonary veins © 2013 Pearson Education, Inc. Figure 18.9 The heart is a double pump, each side supplying its own circuit. Slide 10 Oxygen-poor blood Oxygen-rich blood Right ventricle Pulmonary veins Left atrium Mitral valve Left ventricle Aorta Aortic semilunar valve Aortic Semilunar valve Mitral valve Aorta Left ventricle Left atrium Four pulmonary veins © 2013 Pearson Education, Inc. Figure 18.9 The heart is a double pump, each side supplying its own circuit. Slide 11 Blood Flow Through the Heart Systemic capillaries To body Oxygen-rich blood is delivered to the body tissues (systemic circuit). Pulmonary veins Left atrium Mitral valve Left ventricle Aorta Aortic semilunar valve Aortic Semilunar valve Mitral valve Aorta Left ventricle Left atrium Four pulmonary veins Oxygen-poor blood Oxygen-rich blood © 2013 Pearson Education, Inc. Figure 18.9 The heart is a double pump, each side supplying its own circuit. Both sides of the heart pump at the same time, but let’s follow one spurt of blood all the way through the system. Oxygen-rich blood Superior vena cava (SVC) Inferior vena cava (IVC) Coronary sinus Right atrium Tricuspid valve Pulmonary Semilunar valveRight ventricle Pulmonary trunk SVC IVC Coronary sinus Right atrium Tricuspid valve Right ventricle Pulmonary arteries Pulmonary trunk Pulmonary semilunar valve To heart Oxygen-poor blood returns from the body tissues back to the heart. Oxygen-poor blood is carried in two pulmonary arteries to the lungs (pulmonary circuit) to be oxygenated. To lungs Systemic capillaries Pulmonary capillaries To body Oxygen-rich blood is delivered to the body tissues (systemic circuit). Oxygen-rich blood returns to the heart via the four pulmonary veins. To heart Pulmonary veins Left atrium Mitral valve Left ventricle Aorta Aortic semilunar valve Aortic Semilunar valve Mitral valve Aorta Left ventricle Left atrium Four pulmonary veins Oxygen-poor blood Slide 1 38 Tricuspid valve Right atrium Right ventricle Pulmonary trunk Pulmonary arteries Alveolar capillaries (lungs) Pulmonary veins Left atrium Left ventricle Aorta Blood to systemic circuit Pulmonary valve Mitral valve Aortic valve Venae cavae and coronary sinus Blood from systemic circuit Structural Differences between the Left and Right Ventricles Left ventricle Right ventricle Posterior interventricular sulcus Fat in anterior interventricular sulcus A diagrammatic sectional view through the heart, showing the relative thicknesses of the two ventricles. Notice the pouchlike shape of the right ventricle and the greater thickness of the left ventricle. Structural Differences between the Left and Right Ventricles Dilated Contracted Diagrammatic views of the ventricles just before a contraction (dilated) and just after a contraction (contracted). Left ventricle Right ventricle 41 Path of Blood Through the Heart Tissue cells Tissue cells Alveolus Alveolus Left atrium Mitral valve Aortic valve Left ventricle Right atrium Tricuspid valve Pulmonary valve Inferior vena cava Right ventricle Aorta O2 CO2 O2 O2 CO2 CO2 O2CO2 Systemic capillaries Superior vena cava Alveolar capillaries Systemic capillaries Pulmonary veins Alveolar capillaries Pulmonary artery Anatomy of the Heart • Connective Tissues and the Cardiac Skeleton – Connective Tissue Fibers 1. Physically support cardiac muscle fibers 2. Distribute forces of contraction 3. Add strength and prevent overexpansion of heart 4. Provide elasticity that helps return heart to original size and shape after contraction 43 Aorta Pulmonary trunk Left pulmonary artery Left pulmonary veins Left auricle Left coronary artery Great cardiac vein Left ventricle Apex of the heart Superior vena cava Right auricle Inferior vena cava Small cardiac vein Anterior cardiac vein Right ventricle (a) Left pulmonary artery Aorta Left auricle Circumflex artery Cardiac vein Left ventricle Apex of the heart Superior vena cava Left atrium Right atrium Inferior vena cava Coronary sinus Middle cardiac vein Right ventricle(b) Right pulmonary artery Right pulmonary veins Right coronary artery Anterior interventricular artery (left anterior descending artery) Left pulmonary veins Right pulmonary artery Right pulmonary veins Posterior interventricular artery Anatomy of the Heart • The Blood Supply to the Heart – = Coronary circulation – Supplies blood to muscle tissue of heart – Coronary arteries and cardiac veins Anatomy of the Heart • The Coronary Arteries – Left and right – Originate at aortic sinuses – High blood pressure, elastic rebound forces blood through coronary arteries between contractions 46 Aortic sinus http://meddic.jp/aortic_sinus Anatomy of the Heart • The Cardiac Veins – Great cardiac vein • Drains blood from area of anterior interventricular artery into coronary sinus – Anterior cardiac veins • Empty into right atrium – Posterior cardiac vein, middle cardiac vein, and small cardiac vein • Empty into great cardiac vein or coronary sinus a Coronary Circulation Aortic arch Ascending aorta Right coronary artery Atrial arteries Anterior cardiac veins Small cardiac vein Marginal artery Left coronary artery Pulmonary trunk Circumflex artery Anterior interventricular artery Great cardiac vein Coronary vessels supplying and draining the anterior surface of the heart. b Coronary Circulation Coronary sinus Circumflex artery Great cardiac vein Marginal artery Posterior interventricular artery Posterior cardiac vein Left ventricle Middle cardiac vein Marginal artery Right coronary artery Small cardiac vein Coronary vessels supplying and draining the posterior surface of the heart. Anatomy of the Heart • Heart Disease – Coronary Artery Disease – Coronary artery disease (CAD) • Areas of partial or complete blockage of coronary circulation – Cardiac muscle cells need a constant supply of oxygen and nutrients • Reduction in blood flow to heart muscle produces a corresponding reduction in cardiac performance • Reduced circulatory supply, coronary ischemia, results from partial or complete blockage of coronary arteries Heart Disease and Heart Attacks Narrowing of Artery Lipid deposit of plaque Cross-section Tunica externa Tunica media Cross-section Normal Artery Anatomy of the Heart • Heart Disease – Coronary Artery Disease – Usual cause is formation of a fatty deposit, or atherosclerotic plaque, in the wall of a coronary vessel – The plaque, or an associated thrombus (clot), then narrows the passageway and reduces blood flow – Spasms in smooth muscles of vessel wall can further decrease or stop blood flow – One of the first symptoms of CAD is commonly angina pectoris Anatomy of the Heart • Heart Disease – Coronary Artery Disease – Angina Pectoris • In its most common form, a temporary ischemia (restriction in blood supply to tissues) develops when the workload of the heart increases • Although the individual may feel comfortable at rest, exertion or emotional stress can produce a sensation of pressure, chest constriction, and pain that may radiate from the sternal area to the arms, back, and neck Anatomy of the Heart • Heart Disease – Coronary Artery Disease – Myocardial infarction (MI), or heart attack • Part of the coronary circulation becomes blocked, and cardiac muscle cells die from lack of oxygen • The death of affected tissue produces a nonfunctional area known as an infarct • Heart attacks most commonly result from severe coronary artery disease (CAD) Anatomy of the Heart • Heart Disease – Coronary Artery Disease – Treatment of CAD and Myocardial Infarction • Risk Factor Modification – Stop smoking – High blood pressure treatment – Dietary modification to lower cholesterol and promote weight loss – Stress reduction – Increased physical activity (where appropriate) 56 Coronary Artery Disease • Heart muscle receiving insufficient blood supply – Atherosclerosis, artery spasm or clot – Tx = drugs, bypass graft, angioplasty, stent • Angina pectoris (ischemia) Heart Disease and Heart Attacks Normal Heart Advanced Coronary Artery Disease A color-enhanced DSA scan showing advanced coronary artery disease. Blood flow to the ven- tricular myocardium is severely restricted. A color-enhanced digital subtraction angiography (DSA) scan of a normal heart. Bypass Surgery • The medical name for heart bypass surgery is coronary artery bypass graft (CABG). According to the American Heart Association, CABG involves removing a blood vessel from the chest, arms, or legs and using it to produce a detour or bypass around the blockage. This allows blood to reach the heart again. 58 The Cardiac Cycle • The Cardiac Cycle – Is the period between the start of one heartbeat and the beginning of the next – Includes both contraction and relaxation STOP 60 Heart Actions • The heart chambers function in coordinated fashion • Heart actions are regulated so that atria contract (atrial systole) while ventricles relax (ventricular diastole); followed by ventricles contract (ventricular systole) while atria relax (atrial diastole) (a) (b) Atrial systole LA LV RV RA Atrial diastole Aortic valve open Ventricular systole Tricuspid and mitral valves closed Ventricular diastole Pulmonary valve open Aortic valve closed Pulmonary valve closed Tricuspid and mitral valves open 61 Cardiac Cycle • During a cardiac cycle, the pressure in the heart chambers rise and falls • In atrial systole and ventricular diastole: • Blood flows passively into the ventricles • The remaining 30% of blood is pushed into the ventricles • The A-V valves open and the semilunar valves close • The ventricles relax • This causes an increase in ventricular pressure (a) (b) Atrial systole LA LV RV RA Atrial diastole Aortic valve open Ventricular systole Tricuspid and mitral valves closed Ventricular diastole Pulmonary valve open Aortic valve closed Pulmonary valve closed Tricuspid and mitral valves open •In ventricular systole and atrial diastole: • The A-V valves close • The chordae tendinae prevent the cusps of the valves from bulging too far into the atria • The atria relax • The blood flows into atria • The ventricular pressure increases and opens the semilunar valves • The blood flows into pulmonary trunk and aorta 62 The Cardiac Cycle • Blood Pressure – In any chamber • Rises during systole • Falls during diastole – Blood flows from high to low pressure • Controlled by timing of contractions • Directed by one-way valves The Cardiac Cycle • Cardiac Cycle and Heart Rate – At 75 beats per minute (bpm) • Cardiac cycle lasts about 800 msec – When heart rate increases • All phases of cardiac cycle shorten, particularly diastole 65 Heart Sounds • A heart beat through a stethoscope sounds like “lubb-dupp” • The “lubb” • The first heart sound • It occurs during ventricular systole • The A-V valves are closing •The “dupp” • The second heart sound • It occurs during ventricular diastole • The pulmonary and aortic semilunar valves are closing • A murmur – abnormal heart sound from the cusps not completely closing Cardiac Conduction System • Clumps or strands of specialized cardiac muscle tissue which initiate and distribute impulses throughout the myocardium • The cardiac conduction system coordinates the events of the cardiac cycle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © 2013 Pearson Education, Inc. Figure 18.15a Intrinsic cardiac conduction system and action potential succession during one heartbeat. The sinoatrial (SA) node (pacemaker) generates impulses. 1 Superior vena cava Right atrium Left atrium Subendocardial conducting network (Purkinje fibers) Inter- ventricular septum Anatomy of the intrinsic conduction system showing the sequence of electrical excitation Slide 2 Internodal pathway © 2013 Pearson Education, Inc. Figure 18.15a Intrinsic cardiac conduction system and action potential succession during one heartbeat. The sinoatrial (SA) node (pacemaker) generates impulses. 1 The impulses pause (0.1 s) at the atrioventricular (AV) node. 2 Superior vena cava Right atrium Left atrium Subendocardial conducting network (Purkinje fibers) Inter- ventricular septum Anatomy of the intrinsic conduction system showing the sequence of electrical excitation Slide 3 Internodal pathway © 2013 Pearson Education, Inc. Figure 18.15a Intrinsic cardiac conduction system and action potential succession during one heartbeat. The sinoatrial (SA) node (pacemaker) generates impulses. 1 The impulses pause (0.1 s) at the atrioventricular (AV) node. 2 The atrioventricular (AV) bundle connects the atria to the ventricles. 3 Superior vena cava Right atrium Left atrium Subendocardial conducting network (Purkinje fibers) Inter- ventricular septum Anatomy of the intrinsic conduction system showing the sequence of electrical excitation Slide 4 Internodal pathway © 2013 Pearson Education, Inc. Figure 18.15a Intrinsic cardiac conduction system and action potential succession during one heartbeat. The sinoatrial (SA) node (pacemaker) generates impulses. 1 The impulses pause (0.1 s) at the atrioventricular (AV) node. 2 The atrioventricular (AV) bundle connects the atria to the ventricles. 3 The bundle branches conduct the impulses through the interventricular septum. 4 Superior vena cava Right atrium Left atrium Subendocardial conducting network (Purkinje fibers) Inter- ventricular septum Anatomy of the intrinsic conduction system showing the sequence of electrical excitation Slide 5 Internodal pathway © 2013 Pearson Education, Inc. Figure 18.15a Intrinsic cardiac conduction system and action potential succession during one heartbeat. The sinoatrial (SA) node (pacemaker) generates impulses. 1 The impulses pause (0.1 s) at the atrioventricular (AV) node. 2 The atrioventricular (AV) bundle connects the atria to the ventricles. 3 The bundle branches conduct the impulses through the interventricular septum. 4 The subendocardial conducting network depolarizes the contractile cells of both ventricles. 5 Superior vena cava Right atrium Left atrium Subendocardial conducting network (Purkinje fibers) Inter- ventricular septum Anatomy of the intrinsic conduction system showing the sequence of electrical excitation Slide 6 Internodal pathway Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Purkinje fibers Interatrial septum Left bundle branch Interventricular septum Right bundle branch Junctional fibers AV node SA node AV bundle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (b) Myocardial muscle fibers (a) 72 73 Electrocardiogram • An electrocardiogram or ECG is a recording of electrical changes that occur in the myocardium during the cardiac cycle • It is used to assess the hearts ability to conduct impulses • The deflections in the normal ECG, or waves, include: • P wave – atrial depolarization • QRS complex (three waves) – ventricular depolarization • T wave – ventricular repolarization 75 Regulation of the Cardiac Cycle • The SA node controls the heart rate • There are also sympathetic and parasympathetic fibers that control the heart rate as well • There are also regulatory reflex centers that influence heart rate • Additional factors that may influence heart rate include: • Physical exercise • Body temperature • Concentration of various ions including: • Potassium • Calcium • Parasympathetic impulses decrease heart action • Sympathetic impulses increase heart action 76 Clinical Application Arrhythmias Abnormal electrical activity in the heart Abnormal activity can be too fast (tachycardia-over 100 BPM at rest) or too slow (bradycardia-less than 60 BPM) Can result in cardiac arrest, fainting, or just annoying palpations Fibrillation occurs when small areas of he myocardium contract in an uncoordinated, chaotic fashion Myocardium fails to contract as a whole, and blood is no longer pumped Atrial fibrillation not life threatening; ventricles still pumping blood Ventricle fibrillation—mostly deadly © 2013 Pearson Education, Inc. Other Factors that Influence Heart Rate • Age – Fetus has fastest HR • Gender – Females faster than males • Exercise – Increases HR • Body temperature – Increases with increased temperature © 2013 Pearson Education, Inc. Homeostatic Imbalances • Tachycardia – abnormally fast heart rate (>100 beats/min) – If persistent, may lead to fibrillation • Bradycardia – heart rate slower than 60 beats/min – May result in grossly inadequate blood circulation in nonathletes – May be desirable result of endurance training Homeostatic Imbalance • Congestive heart failure (CHF) – Progressive condition; CO (cardiac output) is so low that blood circulation inadequate to meet tissue needs – Reflects weakened myocardium caused by • Coronary atherosclerosis—clogged arteries • Persistent high blood pressure • Multiple myocardial infarcts • Dilated cardiomyopathy (DCM)-heart muscle disease Homeostatic Imbalance • Pulmonary congestion – Left side fails à blood backs up in lungs • Peripheral congestion – Right side fails à blood pools in body organs à edema • Failure of either side ultimately weakens other • Treat by removing fluid, reducing afterload, increasing contractility 82 Exercise & the Heart • Benefits of aerobic exercise: – increased CO – increased HDL & decreased triglycerides – improved lung fxn – decreased BP – weight control 83 Lifespan Changes • Cholesterol deposition in the blood vessels • Heart enlargement • Death of cardiac muscle cells • Increase in fibrous connective tissue of the heart • Increase in adipose tissue of the heart • Increase in blood pressure • Decrease in resting heart rate 84 87 ——————————————————————————————————————— Chapter – Blood Vessels – Details Page of 47 Zoom Blood Vessels https://youtu.be/K97FoJdv_OI 2 Blood Vessels • The blood vessels are organs of the cardiovascular system • The blood vessels form a closed circuit to and from the heart • The blood vessels include: • Arteries – carry blood away from the ventricles of the heart • Arterioles – receive blood from the arteries and carry blood to the capillaries • Capillaries – sites of exchange of substances between the blood and the body cells • Venules – receive blood from the capillaries • Veins – carry blood toward the atria of the heart 3 Artery Lumen (a) (b) (c) Vein Valve Endothelium of tunica interna Connective tissue (elastic and collagenous fibers) Tunica media Tunica externa c: © The McGraw-Hill Companies, Inc./Al Telser, photographer • Arteries smaller because decrease in diameter allows rapid blood transport • Gets oxygenated blood to the body as fast as possible • Helps produce blood pressure © 2013 Pearson Education, Inc. Figure 19.1a Generalized structure of arteries, veins, and capillaries. Artery Vein Blood Vessels • Differences between Arteries and Veins – Arteri

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