Function of the Valves 109

Aortic Pressure Curve 109

Relationship of the Heart Sounds to

Heart Pumping 109

Work Output of the Heart 110

Graphical Analysis of Ventricular Pumping 110 Chemical Energy Required for Cardiac Contraction: Oxygen Utilization by the Heart 111

Regulation of Heart Pumping 111

Intrinsic Regulation of Heart Pumping—

The Frank-Starling Mechanism 111

Effect of Potassium and Calcium Ions on

Heart Function 113

Effect of Temperature on Heart Function 114

Increasing the Arterial Pressure Load (up to a Limit) Does Not Decrease the Cardiac Output 114

CHAPTER 10 Rhythmical Excitation of the Heart 116 Specialized Excitatory and Conductive System of the Heart 116

Sinus (Sinoatrial) Node 116

Internodal Pathways and Transmission of the Cardiac Impulse Through the Atria 118

Atrioventricular Node, and Delay of Impulse

Conduction from the Atria to the Ventricles 118 Rapid Transmission in the Ventricular

Purkinje System 119

Transmission of the Cardiac Impulse in the

Ventricular Muscle 119

Summary of the Spread of the Cardiac Impulse Through the Heart 120

Control of Excitation and Conduction in the Heart 120

The Sinus Node as the Pacemaker of the

Heart 120

Role of the Purkinje System in Causing Synchronous Contraction of the Ventricular Muscle 121

Control of Heart Rhythmicity and Impulse Conduction by the Cardiac Nerves: The Sympathetic and Parasympathetic Nerves 121

CHAPTER 11 The Normal Electrocardiogram 123

Characteristics of the Normal Electrocardiogram 123

Depolarization Waves Versus

Repolarization Waves 123

Relationship of Atrial and Ventricular Contraction to the Waves of the Electrocardiogram 125

Voltage and Time Calibration of the Electrocardiogram 125

Methods for Recording

Electrocardiograms 126

Pen Recorder 126

Flow of Current Around the Heart During the Cardiac Cycle 126

Recording Electrical Potentials from a Partially Depolarized Mass of Syncytial Cardiac Muscle 126

Flow of Electrical Currents in the Chest

Around the Heart 126

Electrocardiographic Leads 127

Three Bipolar Limb Leads 127

Chest Leads (Precordial Leads) 129

Augmented Unipolar Limb Leads 129

CHAPTER 12 Electrocardiographic Interpretation of Cardiac Muscle and Coronary Blood Flow Abnormalities: Vectorial Analysis 131

Principles of Vectorial Analysis of

Electrocardiograms 131

Use of Vectors to Represent Electrical

Potentials 131

Direction of a Vector Is Denoted in Terms of Degrees 131

Axis for Each Standard Bipolar Lead and

Each Unipolar Limb Lead 132

Vectorial Analysis of Potentials Recorded in Different Leads 133

Vectorial Analysis of the Normal

Electrocardiogram 134

Vectors That Occur at Successive Intervals During Depolarization of the Ventricles— The QRS Complex 134

Electrocardiogram During Repolarization—

The T Wave 134

Depolarization of the Atria—The P Wave 136

Vectorcardiogram 136

Mean Electrical Axis of the Ventricular QRS—And Its Significance 137

Determining the Electrical Axis from

Standard Lead Electrocardiograms 137

Abnormal Ventricular Conditions That Cause Axis Deviation 138

Conditions That Cause Abnormal Voltages of the QRS Complex 140

Increased Voltage in the Standard Bipolar

Limb Leads 140

Decreased Voltage of the Electrocardiogram 140 Prolonged and Bizarre Patterns of the QRS Complex 141

Prolonged QRS Complex as a Result of

Cardiac Hypertrophy or Dilatation 141

Prolonged qRs Complex Resulting from

Purkinje System Blocks 141

Conditions That Cause Bizarre QRS Complexes 141

Current of Injury 141

Effect of Current of Injury on the QRS

Complex 141

The J Point—The Zero Reference Potential for Analyzing Current of Injury 142

Coronary Ischemia as a Cause of Injury Potential 143

Abnormalities in the T Wave 145

Effect of Slow Conduction of the Depolarization Wave on the Characteristics of the T Wave 145

Shortened Depolarization in Portions of the Ventricular Muscle as a Cause of T Wave Abnormalities 145

CHAPTER 13 Cardiac Arrhythmias and Their Electrocardiographic Interpretation Abnormal Sinus Rhythms Tachycardia Bradycardia Sinus Arrhythmia Abnormal Rhythms That Result from Block of Heart Signals Within the Intracardiac Conduction Pathways Sinoatrial Block Atrioventricular Block Incomplete Atrioventricular Heart Block Incomplete Intraventricular Block— Electrical Alternans Premature Contractions Premature Atrial Contractions A-V Nodal or A-V Bundle Premature

Contractions Premature Ventricular Contractions Paroxysmal Tachycardia Atrial Paroxysmal Tachycardia Ventricular Paroxysmal Tachycardia Ventricular Fibrillation Phenomenon of Re-entry—"Circus Movements" as the Basis for Ventricular Fibrillation Chain Reaction Mechanism of Fibrillation Electrocardiogram in Ventricular Fibrillation Electroshock Defibrillation of the Ventricle Hand Pumping of the Heart (Cardiopulmonary Resuscitation) as an Aid to Defibrillation Atrial Fibrillation Atrial Flutter Cardiac Arrest

UNIT The Circulation

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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