Table Of ContentNEUROPHYSIOLOGY OF THE JAWS AND TEETH
NEUROPHYSIOLOGY OF
THE JAWS AND TEETH
Edited by
A. TAYLOR
Sherrington School of Physiology,
St. Thomas's Hospital, London, England
M
MACMILLAN
EDUCATION
Scientific & Medical
© The Macmillan Press Ltd 1990
Softcover reprint of the hardcover 1st edition 1990 978-0-333-42362-2
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First published 1990
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British Library Cataloguing in Publication Data
Neurophysiology of the jaws and teeth.
1. Man. Jaws. Neurophysiological aspects
I. Taylor, A. (Anthony)
612'.311
ISBN 978-1-349-08966-6 ISBN 978-1-349-08964-2 (eBook)
DOI 10.1007/978-1-349-08964-2
Contents
Preface ix
The Contributors XI
1. Specialization of Mammalian Jaw Muscles: Fibre Type
Compositions and the Distribution of Muscle Spindles
A.M. Rowlerson 1
Introduction 1
Structure-Function Relationships at the Macroscopic Level 2
Muscle Fibre Type Composition in Masticatory Muscles 5
Muscle Spindles in the Masticatory Muscles 33
Summary and General Conclusions 41
Appendix 1 43
AppendixZ 43
Appendix3 44
2. Periodontal Mechanoreceptors and Their Functions
R. W. A. Linden 52
Introduction 52
Peripheral Nerve Studies 53
Central Studies 69
The Functional Role of Intraoral Mechanoreceptors 77
Summary 88
3. Jaw Muscle Spindles and Their Central Connections
K. Appenteng 97
Introduction 97
Afferent Properties 97
Sites of Projection of Elevator Spindle Afferents 108
VI Contents
Electrophysiological Studies-Monosynaptic Connections to
Motoneurons 120
Polysynaptic Projections of Spindles to Motoneurons 133
4. Specialization of the Reflexes of the Ja '!s J.P. Lund 142
Introduction 142
The Role of Jaw Reflexes During Locomotion 142
The Pattern of Primary Afferent Activity During Mastication 148
Action of the Jaw Reflexes During Mastication 152
The Control of Reflex Sensitivity During Mastication 154
Conclusions 158
5. Primary Afferent and Descending Cortical Convergence on
the Interneurons in the Border Zone of the Trigeminal Motor
Nucleus: A Comparison Between Trigeminal and Spinal
Interneurons K. A. Olsson and S. Landgren 162
Introduction 162
Methodological Considerations 163
Segmental Interneurons in the Corticospinal Path 166
Interneurons in the Path from the Coronal Gyrus of the
Cerebral Cortex to the Intertrigeminal Area of the Cat 174
Modulation of the Excitability of Interneurons in the NintV
and NVspo-'Y During Mastication 183
Comparison Between the Segmental and the Trigeminal
Interneurons Subserving Motor Control 184
6. Trigemina' Projections to the Cerebellum S. A. Elias 192
Introduction 192
Cerebellar Disorders and Their Effect on Orofacial
Musculature 192
The Cerebellum and Its Afferent Input 194
Second-order Trigeminocerebellar Projections 196
First-order Trigeminocerebellar Projections 202
Trigemino-olivary Projections 206
Electrophysiological Studies of Trigeminal Pathways to the
Cerebellum 210
Possible Functions of the Cerebellum in Jaw Control 224
7. Proprioceptive Control of Jaw Movement A. Taylor 237
Introduction 237
Contents vii
Methodological Considerations 238
Studies of Jaw-closer Muscle Spindles in Natural Movements 248
Fusimotor Recordings 256
Periodontal Afferents 261
Conclusions 263
8. Central Mechanisms or Rhythmical Trigeminal
Activity L. J. Goldberg and S. H. Chandler 268
Introduction 268
Location of Brainstem Neuronal Networks Controlling
Rhythmical Trigeminal Activity 269
Physiological Characteristics of Neurons in Networks
Controlling RTA 275
Intracellular Recordings in Trigeminal Motoneurons 277
Pharmacology of RTA 279
Reticular Formation Influences on RTA 285
Summary and Conclusions 289
9. Brainstem Control or Swallowing: Localization and
Organization or the Central Pattern Generator A. Jean 294
Introduction 294
Central Nervous Structures of the 'Swallowing Centre' 296
Localization of the Swallowing Central Pattern Generator 299
Regulation of the Central Pattern Generator Activity 304
Organization of the Swallowing Central Pattern Generator 307
Conclusion 314
10. Neural Control or Tongue Posture A. R. Lowe 322
Introduction 322
Brainstem Mechanisms 323
Higher Centre Control 331
Tongue Musculature 334
Mandibular Posture 336
Respiratory Implications 341
Orthodontic Postulates 349
Overview 356
11. Perception or Intraoral Stimulation T. Morimoto 369
Introduction 369
Factors Influencing Oral Kinaesthesia 369
viii Contents
Sensory Receptors Responsible for Oral Kinaesthesia 381
Mechanisms of Size Discrimination 385
Comparison of Interdental Size Discrimination with Manual
Size Discrimination 385
Conclusion 387
Index 391
Preface
This book is a collection of comprehensive reviews with some new original
material. They all relate to the functioning of the jaws in the varied tasks of
eating, drinking, phonation and oral manipulation. These are aspects of
motor control which have never been as popular as subjects for study as
have the movements of limbs, but they are of great potential interest
because of the clinical importance of orofacial function and because of the
specializations which are to be seen in the control of movements of the jaws
and related structures. The study of these specializations can be very
illuminating to motor control generally, and with this in mind the authors
have been asked to make comparison, where possible, with other systems,
particularly based on the very intensively investigated neurophysiology of
the spinal cord.
Neurophysiological research on cranial nerve mechanisms has its own
particular technical difficulties, notably the relative inaccessibility of
brainstem structures and the lack of the regular separation into sensory and
motor roots, which is God's gift to spinal cord physiologists. We are well
compensated, however, by such features as the mesencephalic nucleus of
the fifth nerve, the unique periodontal mechanoreceptors, an ultrafast
muscle fibre type and non-symmetrical control of opening and closing
muscles of the jaw. Co-ordination of movements of the tongue in danger
ous proximity to teeth and the safe integration of chewing, talking,
swallowing and breathing are motor skills which must command respect.
They are probably no less demanding than control of the hand, but are
carried on efficiently by all mammals, including those with otherwise very
limited manipulative ability.
The origins of the book were a symposium sponsored by the Phystologic
al Society held at St. Thomas's Hospital Medical School, London, in
November 1985. Rather than produce yet another collection of short
articles, however, it was preferred to give authors, brought together and
X Preface
stimulated by the meeting, the chance to write comprehensive reviews,
which are now brought fully up to date. It is to be hoped that the result will
show clearly the stage which has been reached in the range of related topics
and what should be done next. The subject of orofacial pain has not been
included, because this has its own well-developed literature.
I should like to express my gratitude and appreciation to the internation
al group of workers who have combined to make this treatise available.
Thanks are also due to the following bodies which provided financial
assistance for the original meeting: The Physiological Society of Great
Britain; Special Trustees of St. Thomas's Hospital; The Wellcome Trust;
Sir Halley Stewart Trust; and Muscular Dystrophy Group.
London, September 1989 A.T.
