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Chapter 20, part 1 The Heart
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Learning Objectives Describe the organization of the cardiovascular system. Describe the location and general features of the heart, including the pericardium. Discuss the differences between nodal cells and conducting cells and describe the components and functions of the conducting system of the heart. Identify the electrical events associated with a normal electrocardiogram.
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Learning Objectives Explain the events of the cardiac cycle including atrial and ventricular systole and diastole, and relate the heart sounds to specific events in the cycle. Define cardiac output, heart rate and stroke volume and describe the factors that influence these variables. Explain how adjustments in stroke volume and cardiac output are coordinated at different levels of activity.
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SECTION 20-1 Organization of the Cardiovascular System
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Heart as an Endothermic Organ
Your heart has four chambers (2-cycle pump), and is critical in pumping enough oxygenated blood for you to be able to 1: Keep a high metabolic rate 2: Maintain a constant internal temperature, even in cooler environments 3: Be active under adverse conditions 4: Process food (get energy) relatively quickly
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Two-Cycle Pump—your heart
Blue is one cycle (deoxygenated blood) Red is the other Cycle (oxygenated Blood)
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The cardiovascular system is divided into two circuits
Pulmonary circuit blood to and from the lungs System circuit blood to and from the rest of the body Vessels carry the blood through the circuits Arteries carry blood away from the heart Veins carry blood to the heart Capillaries permit exchange
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Figure 20.1 An Overview of the Cardiovascular System
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SECTION 20-2 Anatomy of the Heart
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The pericardia Visceral pericardium or epicardium Parietal pericardium
Pericardial fluid
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Figure 20.2 The Location of the Heart in the Thoracic Cavity
Figure 20.2a, b
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Figure 20.2 The Location of the Heart in the Thoracic Cavity
Figure 20.2c
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Superficial Anatomy of the Heart
The heart consists of four chambers Two atria and two ventricles Major blood vessels of the heart include Inferior and superior vena cavae Aorta and pulmonary trunk
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Figure 20.3 The Superficial Anatomy of the Heart
Figure 20.3a
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Figure 20.3 The Superficial Anatomy of the Heart
Figure 20.3b, c
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The Heart Wall Components of the heart wall include Epicardium
Myocardium Endocardium
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Figure The Heart Wall Figure 20.4
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Figure 20.5 The Heart Wall and Cardiac Muscle Cells
Figure 20.5a-c
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Internal Anatomy and Organization
Atria Thin walled chambers that receive blood from the vena cavae Ventricles Thick walled chambers separated from the atria by AV valves Chordae tendineae Tendinous fibers attached to the AV valves Papillary muscle and trabeculae carneae Muscular projections on the inner wall of ventricles
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Blood flow through the heart
Right atria Tricuspid valve Right ventricle Pulmonary valve Pulmonary circuit Left atria Bicuspid valve Left ventricle Aortic valve Aorta and systemic circuit
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Blood Flow in the Heart
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Figure 20.6 The Sectional Anatomy of the Heart
PLAY Animation: Diagrammatic Frontal Section through the Heart Figure 20.6a, b
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Figure 20.6 The Sectional Anatomy of the Heart
Figure 20.6c
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Heart chambers and valves
Structural Differences in heart chambers The left side of the heart is more muscular than the right side Functions of valves AV valves prevent backflow of blood from the ventricles to the atria Semilunar valves prevent backflow into the ventricles from the pulmonary trunk and aorta
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Figure 20.7 Structural Differences between the Left and Right Ventricles
Figure 20.7a-c
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Figure 20.8 Valves of the Heart
Figure 20.8a
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Figure 20.8 Valves of the Heart
Figure 20.8b
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Connective Tissues Connective tissue fibers of the heart
Provide physical support and elasticity Distribute the force of contraction Prevent overexpansion The fibrous skeleton Stabilizes the heart valves Physically isolates atrial from ventricular cells
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Blood Supply to the Heart
Arteries include the right and left coronary arteries, marginal arteries, anterior and posterior interventricular arteries, and the circumflex artery Veins include the great cardiac vein, anterior and posterior cardiac veins, the middle cardiac vein, and the small cardiac vein
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Figure 20.9 Coronary Circulation
Figure 20.9a, b
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Figure 20.9 Coronary Circulation
Figure 20.9c, d
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Heart chambers and valves
Structural Differences in heart chambers The left side of the heart is more muscular than the right side Functions of valves AV valves prevent backflow of blood from the ventricles to the atria Semilunar valves prevent backflow into the ventricles from the pulmonary trunk and aorta
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Figure 20.7 Structural Differences between the Left and Right Ventricles
Figure 20.7a-c
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Figure 20.8 Valves of the Heart
Figure 20.8a
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Figure 20.8 Valves of the Heart
Figure 20.8b
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Connective Tissues Connective tissue fibers of the heart
Provide physical support and elasticity Distribute the force of contraction Prevent overexpansion The fibrous skeleton Stabilizes the heart valves Physically isolates atrial from ventricular cells
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Blood Supply to the Heart
Arteries include the right and left coronary arteries, marginal arteries, anterior and posterior interventricular arteries, and the circumflex artery Veins include the great cardiac vein, anterior and posterior cardiac veins, the middle cardiac vein, and the small cardiac vein
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Figure 20.9 Coronary Circulation
Figure 20.9a, b
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Figure 20.9 Coronary Circulation
Figure 20.9c, d
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SECTION 20-3 The Heartbeat
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Cardiac Physiology Two classes of cardiac muscle cells
Specialized muscle cells of the conducting system Contractile cells
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Figure 20.11 An Overview of Cardiac Physiology
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The Conducting System The conducting system includes:
Sinoatrial (SA) node Atrioventricular (AV) node Conducting cells Atrial conducting cells are found in internodal pathways Ventricular conducting cells consist of the AV bundle, bundle branches, and Purkinje fibers PLAY Animation: Heart flythrough
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Figure 20.12 The Conducting System of the Heart
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Impulse Conduction through the heart
SA node begins the action potential Stimulus spreads to the AV node Impulse is delayed at AV node Impulse then travels through ventricular conducting cells Then distributed by Purkinje fibers
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Figure 20.13 Impulse Conduction through the Heart
PLAY Animation: Cardiac Activity Figure 20.13
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The electrocardiogram (ECG)
A recording of the electrical events occurring during the cardiac cycle The P wave accompanies the depolarization of the ventricles The QRS complex appears as the ventricles depolarize The T wave indicates ventricular repolarization
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Figure 20.14 An Electrocardiogram
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Figure 20.14 An Electrocardiogram
Figure 20.14b
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