Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction: Greek Science and the Recognition of Nerve as a Channel
- 2 Galen's Physiology of the Nervous System
- 3 Nerve, Brain, and Soul in the Middle Ages
- 4 Renaissance and the New Physiology
- 5 New Physical and Chemical Models of Nerve in the Enlightenment
- 6 New Systematizations of Nerve Function in the Enlightenment
- 7 Electricity as the Agent of Nerve Action
- 8 Nerve Fiber Form and Transformation
- 9 Wallerian Degeneration: Early and Late Phases
- 10 Nerve Regeneration
- 11 Characterization of Axoplasmic Transport
- 12 Molecular Models of Transport
- 13 Actions of Neurotoxins and Neuropathic Changes Related to Transport
- 14 Purposeful Reflexes and Instinctive Behavior
- 15 Neural Events Related to Learning and Memory
- 16 Epilogue: With Observations on the Relation of the Nervous System to Mind
- Bibliography
- Index
9 - Wallerian Degeneration: Early and Late Phases
Published online by Cambridge University Press: 13 August 2009
- Frontmatter
- Contents
- Preface
- 1 Introduction: Greek Science and the Recognition of Nerve as a Channel
- 2 Galen's Physiology of the Nervous System
- 3 Nerve, Brain, and Soul in the Middle Ages
- 4 Renaissance and the New Physiology
- 5 New Physical and Chemical Models of Nerve in the Enlightenment
- 6 New Systematizations of Nerve Function in the Enlightenment
- 7 Electricity as the Agent of Nerve Action
- 8 Nerve Fiber Form and Transformation
- 9 Wallerian Degeneration: Early and Late Phases
- 10 Nerve Regeneration
- 11 Characterization of Axoplasmic Transport
- 12 Molecular Models of Transport
- 13 Actions of Neurotoxins and Neuropathic Changes Related to Transport
- 14 Purposeful Reflexes and Instinctive Behavior
- 15 Neural Events Related to Learning and Memory
- 16 Epilogue: With Observations on the Relation of the Nervous System to Mind
- Bibliography
- Index
Summary
The loss of sensation and muscle power after a nerve transection has been known from antiquity. In the nineteenth century, when the microscopic structure of the nerve fiber became known, the amputated stump of transected nerves was seen to undergo the characteristic breakdown called Wallerian degeneration. The phenomenon led to a major advance in understanding the different functions of the spinal cord roots; sensory fibers carried in the dorsal roots, motor fibers in the ventral roots, the Bell-Magendie law. On cutting a root, degeneration was seen only in that portion of its fibers separated from the cells in the ganglia. The inference of these results was that the cell bodies are required to maintain viability of their fibers. The pursuit of how this comes about led to the recognition of the neuron doctrine and the need for some means by which materials from the cells are carried out into their fibers, the mechanism of axoplasmic transport, which will be discussed in detail in Chapters 11 and 12. In this chapter, the analysis of Wallerian degeneration is presented and shown to be a two-stage process in which the earliest phase is a beading of the fibers.
THE BELL-MAGENDIE LAW
In a paper he had privately printed in 1811 and that was privately circulated, and only much later publically revealed, the famous English anatomist Charles Bell (1774–1842) reported that injury to the anterior (ventral) portion of the spinal cord marrow caused convulsive muscular movements in vivisected animals, more so than an injury to the posterior (dorsal) portions of the cord.
- Type
- Chapter
- Information
- A History of Nerve FunctionsFrom Animal Spirits to Molecular Mechanisms, pp. 169 - 186Publisher: Cambridge University PressPrint publication year: 2004