The central nervous system : structure and function

532 Pages·2004·101.917 MB·English

by  Per Brodal

The Central Nervous System
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THE CENTRAL NERVOUS SYSTEM
Structure and Function
THIRD EDITION
PER BRODAL
Institute of Basic Medical Sciences
University of Oslo
OXPORD
UNIVERSITY PRESS
2004
OXFORD
UNIVERSITY PRESS
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All rights reserved. No part of this publication may be reproduced,
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Library of Congress Cataloging-in-Publication Data
Brodal, Per.
The central nervous system : structure and function /
Per Brodal.—3rd ed.
p. cm. Includes bibliographical references and index.
ISBN 0-19-516560-8
1. Central nervous system. I. Tide.
QP370.B76 2003 612.8'2—dc21 2003042924
987654321
Printed in the United States of America
on acid-free paper
Preface
This book is intended primarily for use by students of medicine, physical therapy,
and psychology—that is, for use in neuroscience or neuroanatomy courses by stu-
dents who need knowledge of the nervous system as a basis for later clinical study
and practice. The need for a third edition since 1998 attests to the rapid pace of
development in the neurosciences and related fields.
In this edition I have tried to incorporate new findings by rewriting rather
than just adding new material. In this way, the text has not been significantly ex-
panded. Many chapters have been reorganized, and two new chapters deal with
the vestibular system (Chapter 9) and control of eye movements (Chapter 15).
New illustrations have been added, and most others have been redrawn to im-
prove their clarity.
My intentions remain the same as those of my father, Alf Brodal, when he wrote
the Norwegian forerunner of this book more than 50 years ago: to stimulate un-
derstanding rather than memorization of isolated facts, while at the same time fos-
tering a realistic attitude toward our still-limited ability to explain the marvels of
the human brain.
The book aims to present the difficult subject of neuroscience so that those ap-
proaching it for the first time can understand it. Therefore, many details are left
out that might be of great interest to the specialist but would merely obscure the
essentials for the beginner. Everyday experiences and clinical examples are inte-
grated throughout the text to help students link the new material with their prior
knowledge and future profession. The nervous system, however, is exceedingly com-
plex, both structurally and functionally, and much remains to be learned before
we can answer many fundamental questions. Thus, while an undergraduate course
can provide only partial insights, no one is served by a presentation that avoids con-
troversial issues and areas of ignorance. Indeed, pointing out what we do not know
is sometimes better than presenting an oversimplified version. For this reason I
have also discussed how the data were obtained and the limitations inherent in the
various methods.
The main challenge—for both the student and the scientist—is to understand
how the nervous system solves its multifarious tasks. This requires an integrated ap-
proach, drawing on data from all fields of neurobiology, as well as from psychol-
ogy and clinical research. Textbooks sharing this goal nevertheless differ markedly
in how they present the material and where they put the emphasis. Perhaps be-
cause my own field of research is the wiring patterns of the brain, I strongly feel
that knowledge of how the nervous system is built—in particular, how the various
parts are interconnected to form functional systems—is a prerequisite for proper
understanding of data from other fields. A fair knowledge of brain anatomy is es-
pecially important for sound interpretations of the symptoms of brain disease. Text-
books of neuroanatomy often overwhelm the reader with details that are not strictly
relevant for either functional analysis or clinical thinking. Neither does a strong
emphasis on cellular mechanisms at the expense of the properties of neural sys-
tems seem the right choice if the aim is to help readers understand how the brain
V
vi Preface
performs its tasks and how the site of a disease process relates to a patient's symp-
toms. Therefore, neither anatomical nor cellular and molecular details are included
in this book if they cannot in some way be related to function. My hope is that the
book presents a balance of cellular and neural systems material that is right for stu-
dents.
In-depth sections and more advanced clinical material are placed in boxes so
that they should not disturb reading of the main text. Since the needs of readers
differ, however, they are encouraged to read selectively and pick the material they
find most relevant and interesting from their perspective, regardless of whether it
is placed in the main text or in boxes. The frequent subheadings should facilitate
such selective reading. Difficult or complex subjects are preceded with an overview
that may suffice for some readers, while other readers will want to read all the text,
including the boxes.
During the preparation of the former and the present editions, I have received
help from several colleagues, for which I am truly grateful. Jan Bjaalie, Niels Chris-
tian Danbolt, Paul Heggelund, Jan Jansen, Harald Kryvi, Kirsten Osen, Ole Petter
Ottersen, Eric Rinvik, and Jon Storm-Mathisen have all provided constructive crit-
icism and advice. I also gratefully acknowledge the expert help of Kari Ruud, who
prepared most of the drawings, and of Gunnar Lothe and Carina Ingebrigtsen,
who produced the photographic work.
Oslo, Norway P. B.
Contents
A Brief Survey, xi
Studying the Structures and Function of the Nervous System, xiii
Animal Experiments Crucial for Progress, xiii
Ethics and Animal Experiments, xiv
Sources of Error in All Methods, xiv
Revising Scientific Truths from Time to Time, xv
I MAIN FEATURES OF STRUCTURE AND FUNCTION
1. Cellular Elements of Nervous Tissue, 3
Structure of the Neuron, 3
Coupling of Neurons: Pathways for Signals, 10
The Cytoskeleton and Axonal Transport, 15
dial Cells, 17
2. Functional Properties of Neurons, 26
Basis of Excitability and Impulse Propagation, 26
Synaptic Transmission, 35
Neurotransmitters and Their Receptors, 47
3. Parts of the Nervous System, 66
The Spinal Cord, 66
The Brain Stem, 74
The Cerebrum, 83
The Cerebellum, 88
The Coverings of the Brain, 89
The Cerebral Ventricles and the Cerebrospinal Fluid, 90
The Blood Supply of the Central Nervous System, 94
4. Development, Aging, and Plasticity of the Nervous System, 103
Development of the Nervous System, 103
The Nervous System and Aging, 122
Restitution of Function, 125
II SENSORY SYSTEMS
5. Sensory Receptors in General, 135
Sensory Units and Their Receptive Fields, 135
Transduction: The Translation of Stimuli to Action Potentials, 135
vii
viii Contents
Receptor Properties, 137
Classification on the Basis of Receptor Properties, 137
Receptors and Subjective Sensory Experience, 138
6. The Somatosensory System, 139
Exteroceptors: Cutaneous Sensation, 139
Proprioceptors: Deep Sensation, 145
The Sensory Fibers and the Dorsal Roots, 155
The Central Somatosensory Pathways, 161
The Somatosensory Cortical Regions, 172
Pain, 175
7. The Visual System, 183
The Eyeball and the Refracting Media, 183
The Retina, 185
Organization of the Visual Pathways, 194
The Visual Cortex and the Final Processing of Visual Information, 200
8. The Auditory System, 208
The Cochlea, 208
The Auditory Pathways, 215
The Auditory Cortex, 219
9. The Sense of Equilibrium, 221
Structure and Function of the Vestibular Apparatus, 221
Connections of the Vestibular Nuclei, 224
Vestibular Reflexes, 226
Receptors and Reflexes of Importance for Body Balance, 228
Cortical Processing of Vestibular Signals, 231
10. Olfaction and Taste, 233
The Olfactory System, 233
The Sense of Taste, 237
III MOTOR SYSTEMS
11. The Peripheral Motor Neurons and Reflexes, 243
Motoneurons and Muscles, 243
Reflexes, 251
Muscle Tone, 258
Injury of Peripheral Motor Neurons and Regeneration, 261
12. The Central Motor Pathways, 265
The Pyramidal Tract (The Corticospinal Tract), 265
Other Descending Pathways to the Spinal Cord, 271
Control of Automatic Movements, 274
Motor Cortical Areas and Control of Voluntary Movements, 276
Symptoms Caused by Interruptions of Central Motor Pathways
(Upper Motor Neurons), 281
Contents ix
13. The Basal Ganglia, 286
Structure and Connections of the Basal Ganglia, 286
The Ventral Striatum, 296
Functions of the Basal Ganglia, 297
Diseases of the Basal Ganglia, 299
14. The Cerebellum, 303
Subdivisions and Afferent Connections of the Cerebellum, 303
The Cerebellar Cortex and the Mossy and Climbing Fibers, 309
Efferent Connections of the Cerebellum, 312
Cerebellar Functions and Symptoms in Disease, 315
15. Control of Eye Movements, 321
The Eye Muscles and Movements of the Eyes, 321
Central Control of Eye Movements, 323
IV THE BRAIN STEM AND THE CRANIAL NERVES
16. Reticular Formation, 333
Structure and Connections of the Reticular Formation, 333
Functions of the Reticular Formation, 340
Consciousness, 342
Sleep, 345
17. The Cranial Nerves, 349
General Organization of the Cranial Nerves, 349
The Hypoglossal Nerve, 353
The Accessory Nerve, 354
The Vagus Nerve, 355
The Glossopharyngeal Nerve, 358
The Vestibulocochlear Nerve, 359
The Facial and Intermediate Nerves, 359
The Trigeminal Nerve, 361
The Abducens, Trochkar, and Oculomotor Nerves, 364
V THE AUTONOMIC NERVOUS SYSTEM
18. The Peripheral Autonomic Nervous System, 371
General Organization of the Autonomic System, 371
Peripheral Parts of the Sympathetic System, 374
Peripheral Parts of the Parasympathetic System, 380
The Enteric Nervous System, 382
Functional Aspects of the Autonomic Nervous System, 382
Neurotransmitters in the Autonomic Nervous System, 386
Sensory Innervation of Visceral Organs and Visceral Reflexes, 389
19. The Central Autonomic System: Hypothalamus, 397
Centers in the Brain Stem for Coordination of Behavior, 397
Structure and Connections of the Hypothalamus, 398