Electric currents and electromagnetic fields have been applied to biological systems, particularly humans, with both therapeutic and pathological results. This text discusses biological responses to electric currents and electromagnetic fields, including medical applications and shock hazards. It covers fundamental physical and engineering principles of responses to short-term electrical exposure and emphasises human reactions, although animal responses are considered as well, and the treatment covers reactions from the just-detectable to the clearly detrimental. An important new chapter discusses standards for human exposure to electromagnetic fields and electric current and demonstrates how these standards have been developed using the principles treated in earlier chapters.

Inhaltsangabe1 Introduction.- 1.1 General Perspective.- 1.2 Electrical Exposure.- Electrical Fatalities.- Typical Electrical Exposures.- 1.3 Scales of Short-Term Reactions to Contact Current.- Sensory Reactions.- Muscle Reactions.- Cardiac Reactions.- Thermal Reactions.- Electroporation.- 1.4 Reactions to Electric and Magnetic Field Stimulation.- 1.5 Variables Affecting Thresholds.- 2 Impedance and Current Distribution.- 2.1 Dielectric Properties of Biological Materials.- Conductivity and Permittivity.- Cellular Membranes.- Skin Depth.- 2.2 Skin Impedance.- Detailed Structure of Skin.- Equivalent Circuit Models.- Area Proportionality of Skin Admittance.- Skin Capacitance.- Time-Variant and Nonlinear Aspects of Skin Impedance.- 2.3 Total Body Impedance: Low-Frequency and DC.- Distribution of Current and Impedance Within the Body.- Current Through the Heart.- Applicability of Measurements on Corpses.- Statistical Distribution of Impedance.- 2.4 Impedance at Higher Frequencies.- 2.5 Impedance Through Foot Contact.- 2.6 High-Voltage and Transient Properties.- Spark and Contact Components.- Plateau Voltage.- Spark Discharges and Corneal Degradation.- Discharge Impedance.- Variation with Stimulus Location.- Polarity Effects.- Stimulus Time Constants.- Minimum Impedance with Spark Discharge.- Internal Body Impedance.- 2.7 Impedance of Domestic Animals.- 3 Electrical Principles of Nerve and Muscle Function.- 3.1 Introduction.- 3.2 Cellular Membranes.- The Nernst Equation.- 3.3 The Excitable Nerve Membrane.- The Hodgkin-Huxley Membrane.- The Frankenhaeuser-Huxley Membrane.- Species Dependence of Action Potential.- Dynamics.- Propagation of Nerve Impulses.- 3.4 Action Potential Models for Cardiac Tissue.- 3.5 Sensory Transduction.- Intensity Coding.- 3.6 Muscle Function.- 3.7 Synapses.- General Properties.- Synaptic Interactions with In-Situ E-Fields.- 3.8 The Spinal Reflex.- 4 Excitation Models.- 4.1 Introduction.- 4.2 Linear Strength-Duration Model.- Empirical Strength-Duration Relationships.- 4.3 Electrical Cable Representations.- One-Dimensional Cable Models.- Nonlinear Models.- 4.4 Myelinated Nerve Model.- Threshold Criterion.- Position and Number of Nonlinear Nodes.- Suprathreshold Response.- 4.5 Response to Monophasic Stimulation.- Strength-Duration Relations.- Polarity Sensitivity.- Current Density and Electric Field.- Relationships.- 4.6 Response to Biphasic and Repetitive Stimuli.- Strength-Duration Relationships.- Sinusoidal Stimuli.- Repetitive Stimuli.- Nonlinear Interaction of Multiple Waveforms.- 4.7 Parameter Variation Effects.- 5 Electrical Properties of the Heart.- 5.1 Cardiovascular System: General Anatomical and Functional Aspects.- 5.2 Origin and Spread of Excitation.- Autorhythmicity and Geometry of Propagation.- Hierarchy of Pacemaker Activity and Artificial Pacemakers.- 5.3 Elementary Processes of Excitation and Contraction.- Ionic Mechanisms of Excitation.- Mechanism of Contraction.- Excitation-Contraction Coupling.- 5.4 Stimulation, Propagation, and Refractoriness.- Elementary Mechanisms.- Conduction of the Action Potential.- Definition and Mechanism of Refractoriness.- 5.5 Regular and Ectopic Pacemakers.- Elementary Events in Impulse Formation.- Actual and Potential Pacemakers.- Ectopic Pacemakers.- 5.6 Effects of Autonomic Nerves and of Changes in Electrolyte Composition.- Parasympathetic and Sympathetic Innervation.- Chronotropy, Inotropy, and Dromotropy.- Vagal and Sympathetic Tone.- Mechanism of Autonomic Transmitter Actions.- Effects of the Ionic Environment and of Drugs.- 5.7 Electrocardiogram.- ECG Form and Nomenclature; Relation to Cardiac Excitation.- Origin of ECG.- ECG Recording.- Use of the ECG in Diagnosis.- 5.8 Abnormalities in Cardiac Rhythm as Reflected in the ECG.- Rhythms Originating in the AV Junction.- Rhythms Originating in the Ventricles.- Extrasystoles.- Atrioventricular Disturbances of Conduction.- Atrial Flutter and Fibrillation.- Ventricular Flutter and Fibrillation.- 5.9 Mechanism of Flutter and