Organization in the Spinal Cord

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 ofcollaterals 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 thedorsal 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 th