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Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
CHAPTER 20The Cardiovascular System: The Heart
Principles of Anatomy and Physiology
14th Edition
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The purpose of the chapter is to:1. Learn about the components of the
cardiovascular system
2. Focus on the anatomy and physiology of the heart
3. Learn about the cardiac cycle
4. Discuss the various factors that influence heart rate and force of contraction
Introduction
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The heart is located in the mediastinum
Location of the Heart
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The heart is located in the mediastinum
Location of the Heart
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The heart is enclosed and held in place by the pericardium
Pericardium
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The pericardium consists of an outer fibrous pericardium and an inner serous pericardium
The serous pericardium has 2 layers:1. Visceral
2. Parietal
The visceral and parietal layers are separated by the serous cavity, a fluid-filled space
Pericardium
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Anatomy Overview:
Cardiac Muscle
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Cardiac Muscle
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The wall of the heart has 3 layers:1. Epicardium
2. Myocardium
3. Endocardium
Layers of the Heart Wall
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The chambers of the heart include two upper atria and two lower ventricles
Chambers of the Heart
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The chambers of the heart include two upper atria and two lower ventricles
Chambers of the Heart
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The right atrium receives blood from the superior and inferior vena cava and the coronary sinus
Right Atrium
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The right ventricle receives blood from the right atrium and sends blood to the lungs
Right Ventricle
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The left atrium receives blood from the pulmonary veins
Left Atrium
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The left ventricle receives blood from the left atrium and sends blood all over the body
The wall of the left ventricle is much thicker than that of the right ventricle
Left Ventricle
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The fibrous skeleton of the heart:
Forms the foundation for which the heart valves attach
Serves as a point of insertion for cardiac muscle bundles
Prevents overstretching of the heart valves
Acts as an electrical insulator
Fibrous Skeleton
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The valves of the heart open and close in response to pressure changes as the heart contracts and relaxes
Right and left atrioventricular valves Prevent back flow from the ventricles into the atria
Right and left semilunar valves Prevent back flow from the arteries into the ventricles
Heart Valves and Circulation of Blood
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Heart Valves and Circulation of Blood
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When one set of valves is open, the other set is closed
Heart Valves and Circulation of Blood
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Systemic and Pulmonary Circulations
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Coronary Circulation
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The Cardiovascular System
Anatomy Overview:
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Blood flow through coronary arteries delivers oxygenated blood and nutrients to the myocardium
Branches arise from the ascending aorta
Coronary veins remove carbon dioxide and wastes from the myocardium
Branches converge at the coronary sinus
Coronary Circulation
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Coronary Circulation
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Cardiac Muscle Tissue
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Cardiac Muscle Tissue
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Cardiac muscle cells are self-excitable, and therefore, autorhythmic
Cardiac muscle cells repeatedly generate spontaneous action potentials that then trigger heart contractions
These cells form the conduction system, which is the route for propagating action potentials through the heart muscle
The Conduction System
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The Conduction System
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The Conduction System
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Cardiac Conduction
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The autorhythmic fibers in the SA node are the natural pacemaker of the heart because they initiate action potentials most often
Signals from the nervous system and hormones (like epinephrine) can modify the heart rate and force of contraction but they do not set the fundamental rhythm
Influences on the Conduction System
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An action potential in a ventricular contractile fiber is characterized by a rapid depolarization, plateau, and repolarization
Action Potential in a Ventricular Fiber
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Cardiac muscle generates ATP via anaerobic cellular respiration and creatine phosphate as backups to aerobic respiration
ATP Production in Cardiac Muscle
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An EKG is a recording of the electrical changes that accompany each heart beat
Electrocardiogram (EKG or ECG)
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Action Potential Propagation Through the Heart
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One cardiac cycle consists of the contraction (systole) and relaxation (diastole) of both atria, rapidly followed by the systole and diastole of both ventricles
Electrical events
Pressure changes
Heart sounds
Volume changes
Mechanical events
The Cardiac Cycle
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The Cardiac Cycle
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Cardiac Cycle
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Electrical Events
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Pressure Changes
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Heart Sounds
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Volume Changes
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Mechanical Events
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CO is the volume of blood ejected from the left or right ventricle into the aorta or pulmonary trunk each minute
Stroke volume (SV) is the amount of blood pumped out of the ventricle in one beat
CO (mL/min) = SV (mL/beat) x HR (beats/min)
Cardiac Output (CO)
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Cardiac Output and the Factors That Influence It
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Cardiac Output
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3 factors regulate stroke volume:1. Preload
2. Contractility
3. Afterload
Regulation of Stroke Volume
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Several factors regulate heart rate: Autonomic nervous system
Hormones
Ions
Age
Gender
Physical fitness
Temperature
Regulation of Heart Rate
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Nervous System Regulation of the Heart
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Factors that Increase Cardiac Output
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Regular aerobic exercise can: Increase cardiac output
Increase HDL
Decrease triglycerides
Improve lung function
Decrease blood pressure
Assist in weight control
Exercise and the Heart
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Help for Failing Hearts
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Development of the Heart
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Development of the Heart
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Coronary artery disease Atherosclerotic plaques Congenital heart defects Arrhythmia Congestive heart failure
Disorders: Homeostatic Imbalances
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End of Chapter 20
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