Organization in the Spinal Cord
The Anatomy and Physiology of Identified Neurones
Published on 1. October 1981
Book
Hardback
XII, 238 pages
978-3-540-10549-7 (ISBN)
Description
The research described in this book arose, in large part, from a sense of frustration. For a number of years I had been studying the physiology of the spinocervical tract, a somatosensory pathway, in the cat's spinal cord. But I did not know, precisely, where the cells of origin of the tract were located and therefore did not know what they looked like or whether there were any correlations between structure and function. It was true that electrophysiolo gical experiments had indicated their probable situation in the dorsal horn, and anatomical work had described the morphology of cells that were likely to give rise to the axons of the tract; but this was not satisfactory. With the publication, by Stretton and Kravitz in 1968, of the Procion Yellow ionophoretic method for intracellular staining, a new tool became available for studying the morphology of physiologically identified neurones. We used the techniques and, although very pleased with the beautiful appearance of the dendritic trees of neurones seen in the fluorescence microscope, we were again frustrated, this time by the inability of Procion Yellow to stain axons for any considerable length. Therefore, P. K. Rose and P. J. Snow and I began to try to develop a method that would stain the axon, together with its collaterals, in addition to the soma and dendrites of an intracellularly re corded neurone.
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Content
1 Spinal cord organization: an introduction.- A. Cytoarchitectonic organization of the spinal cord: Rexed's scheme.- B. An assessment of spinal cord cytoarchitectonics.- C. Physiological classifications of dorsal horn neurones.- D. Resume of spinal cord anatomy.- I. Primary afferent fibres.- 1. Entrance into the spinal cord.- 2. Collaterals.- II. Identified neurones in the spinal cord.- 1. Cells of origin of ascending pathways.- a) Spinocervical tract.- b) Post-synaptic dorsal column pathway.- c) Spinothalamic tract.- d) Dorsal spinocerebellar tract.- e) Ventral spinocerebellar tract.- f) Other ascending tracts.- 2. Identified interneurones with short axons.- a) Renshaw cells.- b) la inhibitory interneurones.- 3. Motoneurones.- 2 Axons innervating hair follicle receptors.- A. Physiology of hair follicle afferent units.- I. Classification.- II. Responses to hair movement.- III. Receptive fields.- B. Central projections of hair follicle afferent fibres.- C. Morphology of axons innervating hair follicle receptors.- I. Entry of axons into the spinal cord, branching and collateral distribution.- II. Morphology of collaterals and their arborizations.- III. Synaptic boutons.- 1. Morphology.- 2. Distribution.- 3. Density.- IV. Organization of collaterals in the dorsal horn.- 1. Organization of collaterals from a single axon.- 2. Somatotopic organization.- 3 Axons innervating rapidly adapting mechanoreceptors in glabrous skin.- A. Axons innervating Pacinian corpuscles.- I. Pacinian corpuscles and their response properties.- II. Central projections of afferent fibres innervating Pacinian corpuscles.- III. Morphology of axons innervating Pacinian corpuscles in the foot and toe pads.- 1. Entry of axons into the spinal cord, branching and collateral distribution.- 2. Morphology of collaterals and their arborizations.- 3. Synaptic boutons.- a) Morphology and distribution.- b) Density.- 4. Organization of collaterals in the dorsal horn.- B. Axons innervating rapidly adapting mechanoreceptors in glabrous skin.- I. The receptor and its response properties.- II. Central projections of afferent fibres innervating rapidly adapting mechanoreceptors in the foot and toe pads.- III. Morphology of axons innervating rapidly adapting mechanoreceptors.- 1. Entry of axons into the spinal cord, branching and collateral distribution.- 2. Morphology of collaterals and their arborizations.- 3. Synaptic boutons.- 4. Organization of collaterals in the spinal cord.- 4 Axons innervating slowly adapting Type I mechanoreceptors.- A. Morphology of the Type I receptor.- I. In hairy skin.- II. In glabrous skin.- B. Physiology of Type I units.- I. From hairy skin.- II. From glabrous skin.- C. Central projections of Type I afferent fibres.- D. Morphology of axons innervating Type I receptors.- I. Entry of axons into the spinal cord, branching and collateral distribution.- II. Morphology of collaterals and their arborizations.- III. Synaptic boutons.- 1. Morphology.- 2. Distribution.- 3. Density.- IV. Organization of collaterals in the dorsal horn.- 5 Axons innervating slowly adapting Type II mechanoreceptors.- A. Morphology of the Type II receptor.- B. Physiology of Type II units.- C. Central projections of Type II afferent fibres.- D. Morphology of axons innervating Type II receptors.- I. Entry of axons into the spinal cord, branching and collateral distribution.- II. Morphology of collaterals and their arborizations.- III. Synaptic boutons.- 1. Lamina III and dorsal lamina IV.- 2. Ventral lamina IV.- 3. Lamina V and dorsal lamina VI.- IV. Organization of collaterals in the dorsal horn.- 6 Spinocervical tract neurones.- A. Physiology of the spinocervical tract.- I. Types of unit in the tract.- II. Actions of descending control systems.- III. Transmission of information through the tract.- B. Anatomy of the spinocervical tract.- I. Location of neurones.- II. Density and distribution of neurones.- III. Somatotopic organization.- IV. Morphology of neurones.- 1. Somata and dendritic trees.- 2. Dendritic spines.- 3. Axons and axon collaterals.- 4. Synaptic boutons.- C. Relationships between the anatomy and the physiology of spinocervical tract neurons.- I. Receptive field position and dendritic trees.- II. Receptor input and morphology.- 1. Dendritic trees.- 2. Axon collaterals.- 3. Relationships between dendritic trees and receptive fields of adjacent neurons.- 4. Relationships between dendritic trees and hair follicle afferent fibre collaterals.- 7 Relationships between hair follicle afferent fibres and spinocervical tract neurones.- A. Anatomy of the relationships between hair follicle afferent arborizations and spinocervical tract neurones.- I. Relationships where the afferent fibre and the neurone had receptive fields on different areas of skin: the negative results.- II. Relationships where the receptive field of the neurone contained the field of the afferent fibre: the positive results.- Positions of terminal arborizations of afferent fibres and dendritic trees of neurones.- Number of afferent collaterals distributed to each cell...- 3. Contacts between afferent fibres and neurones.- a.) Numbers and positions of synapses and their relationships to receptive field positions.- b.) Types and arrangements of synaptic contacts.- 4. Conclusions.- 8 Neurones with axons ascending the dorsal columns.- A. Physiology of neurones with axons ascending the dorsal columns.- I. Response properties.- II. Input from non-primary sources.- III. Axonal conduction velocities.- B. Anatomy of neurones with axons ascending the dorsal columns...- I. Location.- II. Density.- III. Cellular anatomy.- 1. Size of cell bodies.- 2. Dendritic trees.- 3. Axonal projections.- 4. Axon collaterals.- C. Organization of the post-synaptic dorsal column pathway.- I. Correlations between form and function of the neurones...- II. Comparison with the spinocervical tract.- 9 Other dorsal horn neurones.- A. Dorsal horn neurones with unidentified axonal projections.- I. Neurones with somata in lamina III.- II. Neurones with somata in lamina IV.- III. Neurones with somata ventral to lamina IV.- IV. Conclusions.- 10 The organization of the dorsal horn.- A. Organization of input from the skin.- I. Segregation of input according to axonal diameter and afferent unit type.- II. Specificity of the morphology of axon collateral arborizations according to afferent unit type.- III. Receptive field transformation.- IV. Somatotopic organization.- V. Collateral spacing.- B. The neurones of the dorsal horn.- I. Lamina I (the postero-marginal cell layer).- 1. Anatomy.- a) Dendritic organization.- b) Axonal projections.- 2. Physiological properties.- II. Lamina II (the substantia gelatinosa).- 1. Anatomy.- 2. Physiology.- III. Laminae III-VI.- 1. Anatomy.- a) Dendritic trees..- b) Axonal projections.- c) Somatotopic organization.- C. Descending input to the dorsal horn.- I. Descending pathways: actions and terminations.- 1. Corticospinal tract.- 2. Raphe spinal system.- 3. Reticulospinal pathways.- 4. Other descending systems.- II. Summary.- 11 Afferent fibres from primary endings in muscle spindles.- A. Central projections of muscle spindle primary endings.- B. Morphology of Group la afferent fibres.- I. Entry of axons into the spinal cord, branching and collateral distribution.- II. Morphology of collaterals.- III. Terminal arborizations.- 1. In the intermediate region (lamina VI).- 2. In the la inhibitory interneurone region (lamina VII).- 3. In the motor nuclei (lamina IX).- IV. Synaptic boutons.- 1. In the intermediate region (lamina VI).- 2. In the la inhibitory interneurone region (lamina VII).- 3. In the motor nuclei (lamina IX).- V. Organization of collaterals.- 12 Afferent fibres from Golgi tendon organs.- A. Central projections of afferent fibres from tendon organs.- I. Afferent fibres from tendon organs.- II. Central effects of lb input: autogenetic inhibition.- III. Location of interneurones excited by lb afferent fibres.- B. Morphology of axons innervating Golgi tendon organs.- I. Entry of axons into the spinal cord, branching and collateral distribution.- II. Morphology of lb collaterals.- III. Terminal arborizations and synaptic boutons of collaterals...- IV. Organization of collaterals.- 13 Afferent fibres from secondary endings in muscle spindles.- A. Central projections of axons from muscle spindle secondary endings.- I. Terminations of Group II fibres.- II. Location of neurones activated by Group II axons.- III. Central effects of impulses in Group II fibres.- B. Morphology of axons innervating muscle spindle secondary endings.- I. Entry of axons into the spinal cord, branching and collateral distribution.- II. Morphology of collaterals.- III. Terminal arborizations and synaptic boutons.- IV. Organization of collaterals.- 14 Relationships between Group la afferent fibres and motoneurones.- A. ?-Motoneurones.- I. Anatomy.- II. Electrophysiology.- B. Actions of la afferent fibres upon motoneurones.- C. Ia afferent fibre terminations upon motoneurones.- I. Terminations upon motoneuronal somata and proximal dendrites.- II. Terminations upon dendritic trees.- III. Conclusions.- Appendix 1 Methods.- A. Electrophysiological methods.- I. Solutions for intracellular ionophoresis of horseradish peroxidase.- II. Microelectrodes.- III. Intracellular injection of horseradish peroxidase.- IV. Histological methods.- Appendix 2 Nomenclature.- A. Anatomy of the spinal grey matter.- B. Nomenclature for somatosensory neurons.- I. Afferent input.- II. Location of the neuronal soma.- References.