SECOND EDITION

• ntma

MECHANISMS AND ADAPTATIONS

Roger Eckert UNIVERSITY OF CALIFORNIA, LOS ANGELES

With Chapters 13 and 14 by

David Randall UNIVERSITY OF BRITISH COLUMBIA

[E W. H. FREEMAN AND COMPANY San Francisco

Contents

Preface XV The Biological Importance of pH 24 The Henderson-Hasselbalch Equation 25

Acknowledgments XVll Buffer Systems 25 Electric Current in Aqueous Solutions 26

CHAPTER I The Meaning of Physiology I Box 2-1 Electrical Terminology

Why Ammal Physiology? and Conventions 28

Physiology and Medicine 2 Ion Selectivity 29 Physiology and the Human Experience 2 Biological Molecules 31 Central Themes in Physiology 3 Lipids 32

Function Is Based on Structure 3 Carbohydrates 33 Genetics and Physiology 4 Proteins 34 The Principle of Homeostasis 5 Nucleic Acids 41

Box 1-1 The Feedback Principle 6

The Literature of Physiological Sciences 7 CHAPTER 3 Enzymes and Energetics 47 Energy: Concepts and Definitions 48

CHAPTER 2 Physical and Chemical Concepts 11 Chemical Energy Transfer

by Coupled Reactions 51 Atoms, Bonds, and Molecules 13 ATP and the High-Energy Phosphate Group 53 The Fitness of H, 0, N, and C for Life 15 T emperature and Reaction Rates 55 Water 16 Enzymes 57

The Water Molecule 17 Enzyme Specificity 58 . . Properties of Water 18 Ca talytic Activity 59

Water as a Solvent 18 Temperature and Reaction Rates 59 Solutions and Their Colligative Properties 21 Modulation of Enzyme Activity 60 Solutions of Electrolytes 22 Enzyme Kinetics 61

Ionization of Water 22 Enzyme-Substrate Affinity 63 Acids and Bases 23 Enzyme Inhibition 64

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Metabolic Regulatory Mechanisms 66 Ion Gradients as Sources of Cell Energy

Genetic Control of Enzyme Synthesis 66 Cotransport

Metabolic Feedback Inhibition 68 Coun tertransport

Enzyme Activation 68 Membrane Selectivity

Metabolic. Production of ATP 68 Selectivity for Electrolytes

Oxidation, Phosphorylation, Selectivity for Nonelectrolytes

and Energy Transfer 72 Pinocytosis and Exocytosis

The Electron-Transferring Coenzymes 73 Cell-Cell Junctions

The Electron-Transport Chain 75 Gap Junctions

Glycolysis 77 Tight Junctions

Tricarboxylic Acid (Krebs) Cycle 81 Epithelial Transport

Efficiency of Energy Metabolism 83 Active Salt Transport

Oxygen Debt 84 Across an Epithelium

Transport of Water

CHAPTER 4 Permeability and Transport 89 CHAPTER 5 Ions and Excitation

Membrane Composition 90 Membrane Excitation Membrane Organization 93 Passive Electrical Properties of Membranes

Simple Bilayer Models 93 Membrane Capacitance

Box 4-1 Evidences for the Lipid Box 5-1 Capacitance and Time Constant Bilayer Membrane 95

95 Membrane Conductance

The Fluid Mosaic Model Equilibrium Potentials Subunit Models 96

Physical Factors in Membrane Permeation 98 The Nernst Relation

Diffusion 98 Box 5-2 Charge Separation by Membranes

Membrane Flux 99 Box 5-3 Derivation of the Nernst Equation

Osmosis 100 The Resting Potential

Osmolarity and Tonicity 101 Passive Charge Distribution

Electrical Influences on Ion Distribution 102 The Role of Active Transport

Donnan Equilibrium 102 Release of Stored Electrical Energy

Osmotic Properties of Cells 104 Ionic Basis of the Action Potential

Ionic Steady State 104 General Properties

Cell Volume 105" The Sodium Hypothesis

Mechanisms of Passive Permeation 107 Box 5-4 The Voltage-Clamp Method

Box 4-2 Artificial Bilayers 108 The Sodium Channel

Diffusion Through Membrane Channels 109 The Hodgkin Cycle

Box 4-3 Antibiotic Ionophores 110 Box 5-5 Current-Voltage Relations

Simple Diffusion Through the Lipid Bilayer 111 The Potassium Current

Facilitated Transport 112 Summary of Ionic Events

Active Transport 113 During the Action Potential

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Changes in Ion Concentration During Excitation

Calcium and Membrane Excitability

The Calcium Channel

The Calcium-Dependent Potassium Channel

Surface-Charge Screening by CaH

Pacemaker Potentials

CHAPTER 6 Propagation and Transmission of Signals

Nerve Cells The Two Classes of Signals

Employed by Neurons Passive Spread of Electrical Signals Propagation of Nerve Impulses

Box 6-1 Extracellular Signs of Impulse Conduction

Velocity of Propagation

Box 6-2 Axon Diameter and Conduction Velocity

Saltatory Conduction

Concept of the Synapse Transmission at Electrical Synapses Transmission at Chemical Synapses

Morphology of Chemical Synapses Synaptic Potentials

Box 6-3 Pharmacological Agents Useful in Synaptic Studies

Synaptic Currents Reversal Potential Postsynaptic Inhibition

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Box 6-4 Calculations ofReversal Potential 201

Presynaptic Inhibition 203 Postsynaptic Receptors and Channels 204

The Acetylcholine Receptor 204 ACh-Activated Channels 205

Decreased Postsynaptic Conductances 206 Transmitter Substances 206

Biogenic Amines 208

Amino Acids

N europeptides Endogenous Opioids

Release of Transmitter Substances Quantal Nature of Release

Depolarization-Release Coupling

Synaptic Integration Summation

Synaptic Plasticity Facilitation Posttetanic Potentiation

Chemical Modulation of Transmitter Release

CHAPTER 7 Sensory Mechanisms

Receptor Cells as Sensory Transducers

Steps Between Stimulus and Sensory Output

Intensity Coding Input-Output Relations Range Fractionation

Determinants of Receptor Sensitivity

Receptor Adaptation

Contents

Mechanisms for Enhanced Sensitivity Efferent Control of Receptor Sensitivity Feedback Inhibition of Receptors

Chemoreception Mechanoreception

Hair Cells

Organs of Equilibrium The Mammalian Ear

Structure and Function of the Cochlea Excitation of the Cochlear Hair Cells

Frequency Analysis by the Cochlea

Box 7-1 Von Bekesy's Model of the Cochlea

Electroreceptors Thermoreceptors Photoreceptors

Invertebrate Photoreceptor Cells Correlates of Visual Phenomena Photoreceptor Adaptation in Limulus

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Visual Receptor Cells of Vertebrates 265 Geomagnetic Cues 335 Asynchronous Flight Muscles 377 Neurohypophysial Hormones 429

267 Genetics and Instinctive Behavior 336 Cardiac Muscle 379 Adenohypophysial Hormones 432

Box 7-2 The Electroretinogram Genetic Dissection of Neural Mechanisms 339 Smooth Muscle 381 Hypothalamic Control

Visual Pigments 270 Musculoskeletal Mechanics 383 of the Adenohypophysis 433

Photochemistry of Visual Pigments 271 Metabolic and Developmental Hormones 437

Color Vision 274 CHAPTER 9 Muscle and Movement 343 Glucocorticoids 437

Optic Mechanisms 276 Structural Basis of Contraction 343 CHAPTER J0 Motility of Cells 391 Thyroid Hormones 439

Compound Eyes 277 Substructure of the Myofilaments 344

The Catecholamines 442

The Vertebrate Eye 279 The Molecules of Motility 391 Insulin and Glucagon 442

Sliding-Filament Theory 349 Contractile Proteins 392 Growth Hormone 444 Length-Tension Curve 349 Regulatory Proteins 394 Hormonal Regulation of Electrolyte Balance 444

Cross-Bridge Function and the Production of Force 350

Chemistry of Cytoplasmic Motility 395 Prostaglandins 448 Amoeboid Locomotion 396 Sex Hormones 448

CHAPTER 8 Neural Processing and Behavior 285 Chemistry of Cross-Bridge Activity 351 Cilia and Flagella 399 Reproductive Cycles 451 Cross-Bridge Activity

Evolution of Nervous Systems 287 and Muscle Contraction 351

Types of Movements 400 Sex Hormones and Behavior 457

Vertebrate Nervous Systems 290 Fine Structure 402 The Endocrine System of Insects

Major Parts of the Central Nervous System 292 Role of Calcium in Contraction 354

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Cross-Bridge Activation 354 Chemistry of Cilia and Flagella 404 Regulation of Insect Development 458

The Autonomic Nervous System , 294 Mechanisms of Flagellar Bending 404 The Second-Messenger Concept 463

Neural Circuits 296 Box 9-1 Extracted Cell Models 355 Sliding-Tubule Hypothesis 405 cAMP as Second Messenger 463

Sensory Filter Networks 300 Propagation of Bending Cross-Bridge Inactivation Multiple Actions of cAMP 465

Lateral Inhibition 301 and Muscle Relaxation 357 Along the Axoneme 407

Visual Processing in the Vertebrate Retina 304 Electromechanical Coupling 357 Coordination of Ciliary Movement 409 Box 11-1 Amplification

Information Processing Membrane Potential and Contraction 358 Spontaneity and Beating Frequency 409 of Hormone Action 468

in the Visual Cortex 309 The Sarcotubular System 359 Ciliary Reversal 410 Hormone-Induced Mobilization

Box 8-1 Specificity of Neuronal The Sarcoplasmic Reticulum 362 Metachronism 413 of Glucose: A Biochemical Model

Connections and Interactions 313 Calcium Release for cAMP as Second Messenger 469

Neuromotor Networks 314 by the Sarcoplasmic Reticulum 362 Cyclic GMP as Second Messenger 469

The Myotatic Reflex 314 Contraction and Relaxation Summarized 364 CHAPTER 11 Chemical Messengers Calcium as Intracellular Messenger 470

Efferent Control Mechanical Properties of Contracting Muscle 365 and Regulators 417 Calcium-Binding Proteins: Calmodulin 472

Through the Gamma Loop 316 Sarcomere Length Hormones as Messengers 418 Multiple Receptors: Convergent

and Contractile Properties 366 and Divergent Pathways 473

Golgi Tendon Reflex 318 Structural Classification of Hormones 419 Interactions Between CaH Latent Period 366

The Flexion Reflex Functional Classification 420 and Cyclic N ucleotides 474

and Reciprocal Innervation 319 Force-Velocity Relations 367 Identification of Endocrine Glands 367

Hormone Action on Genetic Mechanisms 477

Programmed Behavior 320 Series Elastic Components and Hormones 420

Centrally Generated Motor Rhythms 320 Active State 368 Regulation of Hormone Secretion 422

Fixed Action Patterns 323 Twitch and Tetanus Tensions 370 Feedback Control 422

Behavior in Animals Without Nervous Systems 325 Energy, Heat, and Work 370 Intracellular Packaging and Storage

Animal Orientation 328 Metabolic Subtypes of Striated Muscle 371 of Hormones 423 CHAPTER 12 Osmoregulation and Excretion 483

Taxes and Corrective Responses 328 Neural Control of Muscle Contraction 373 Secretory Mechanisms 425 General Considerations 483

Vibrational Orientation 331 Vertebrate Neuromotor Organization 373 Neuroendocrine Relations 427 Problems of Osmoregulation 486

Echolocation 332 Arthropod Neuromuscular Organization 375 Neurosecretion 428 Factors Influencing Obligatory Exchanges 487

Animal Navigation 333 Box 9-2 Trophic Effects The Mammalian Endocrine System 429 Osmoregulators and Osmoconformers 489

Clock-Compasses 334 of Nerves on Muscles 376 Hypothalamus and Pituitary 429 Epithelium as the Osmoregulatory Tissue 490

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Specific Dynamic Action 697

Energy Storage 697

Body Size and Metabolic Rate 697

Energetic Cost of Locomotion 700

Animal Size, Velocity, and Cost of Locomotion 700

Physical Factors Influencing Locomotion 701

Effect of Reynolds Number 704

Aquatic, Aerial, and Terrestrial Locomotion 705

Temperature Classifications of Animals 708

Geographic Factors 711

Effects of Temperature on Animals 711

Temperature-Dependence of Metabolic Rate 711

Thermal Acclimation 713

Determinants of Body Heat and Temperature 714

Temperature Relations of Ectotherms 716

Ectotherms in Cold Environments 716

Endothermy in Heterotherms 717

Ectotherms in Hot Environments 721

Temperature Relations of Endotherms 721

Thermal Neutral Zone 721

Thermogenesis 723

Box 16-2 Physical Concepts of Heat and Temperature 724

Endothermy in Cold Environments

Countercurrent Heat Exchange Low-Temperature Lipids Endothermy in Hot Environments

Evaporative Cooling Thermostatic Regulation of Body Temperature

The Mammalian Thermostat

N onmammalian Thermoregulatory Centers

Fever Thermoregulation During Exercise

Dormancy

Appendix 1: SI Units

Appendix 2: Selected Atomic Weights

Appendix 3: Conversions, Formulas, Physical and Chemical Constants, Dtifinitions

Glossary

Index rif Names

Index of Topics

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Preface

The diversity and adaptations of the several million species that make up the animal kingdom provide end­less fascination and delight to those who love nature. Not the least of this pleasure derives from a consider­ation of how the bodies of animals function. At first it might appear that with so many kinds of animals adapted to such a variety of life-styles and environ­ments, the task of even beginning to understand and appreciate the physiology of animals would be over­whelming. Fortunately (for scientist and student alike), the concepts and principles that provide a basis for understanding animal function are relatively few, for evolution has been conservative as well as inventive. The basic principles and mechanisms of animal physi­ology form the central theme of this book.

A beginning course in physiology is a challenge for both teacher and student because of the inter­disciplinary nature of the subject. Not all students, even by their junior and senior years, have had expo­sure to all the chemical, physical, and biological subject matter required for an adequate background. On the other hand, most students are eager to come to grips with the subject and get on with the more exciting levels of modern scientific insight. For this reason, this book has been organized to present the essential background material in a way that allows students to review it on their own and go on quickly to the substance of animal function and to an understanding of its experimental elucidation.

Animal Physiology develops the major ideas in a simple

and direct manner, stressing principles and mechanisms over the compilation of information and illustrating the functional strategies that have evolved within the bounds of chemical and physical possibility. Examples are selected from the broad spectrum of animal life, ranging from the protozoa at one end to our species and other vertebrates at the other end. Common prin­ciples, rather than exceptions, a re emphasized. Thus, the more esoteric and peripheral details intentionally receive only passing attention, or none at all, so as not to distract from central ideas. Math is used where essential, but priority is given to the development of a qualitative and intuitive understanding.

The ideas developed in the text are illuminated and augmented by liberal use of illustrations and paren­thetical "boxes." Other pedagogical aids are an 1100-word glossary and various chapter-end materials, in­cluding summaries, exercises, suggested readings, and lists of literature cited. References to the literature within the body of the text and in figure legends have been made unobtrusively, but with enough fre­quency so that the student can become aware of the role of scientists and their literature in the development of the subject. The text in places uses the device of a narrative describing actual, composite, or thought experiments to provide a feeling for methods of in­vestigation while presenting information.

The chapters can be grouped into five sections. The first two chapters are intended primarily as an introduction and for review of the essential physical

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