11.0 NERVOUS TISSUE: INTRODUCTION
The nervous tissue comprises the following elements:
11.2 - images: Peripheral nervous tissue
Peripheral nerves are formed by bundles of nerve fibers which originate from neurons in the gray matter of the spinal cord (anterior horns) and in the spinal ganglia (aggregations of neurons outside the central nervous system).
See: 11.2 POJA-L3226 et al; 11.2 POJA-L3243 et al; 11.2.1 POJA-L3178 et al; 11.3 POJA-L3132 et al.
The peripheral nerve is composed of long nerve cell processes and contain myelinated and non-myelinated nerve fibers.
A peripheral myelinated nerve fiber is an axon enclosed by a continuous basal lamina (or external lamina). The fiber is subdivided in internodi which are linked together and each internodus is governed by one Schwann cell.
See: 11.2 POJA-L3231 et al; 11.2 POJA-L3249 et al; 11.2 POJA-L3252 et al.
Each nerve cell possess a nucleus surrounded by the cytoplasm (perikaryon). The nerve cell with its processes (axon and dendrites) forms a neuron which is the functional and anatomical unit of the nervous system. The axon conducts signals over considerable distances. The dendrites are branching elaborate extensions of the perikaryon and collect or receive impulses.
See: 11.2 POJA-L3275 et al; 11.5 POJA-L3019 et al; 11.5 POJA-L3071 et al.
Synapses are membranous contact points between the neurons where e.g. an axon of one neuron touch the cell membrane of another neuron.
See: 11.2.1 POJA-L3311 et al; 11.3 POJA-L3141 et al; 11.5 POJA-L3079 et al.
A large number of the processes are enveloped by a phospholipid sheath, the myelin sheath which is white in living tissue. Hence the name white matter in the central nervous system versus the gray matter that is composed of aggregations of neurons.
See: 11.2 POJA-L2937 et al; 11.2 POJA-L3249 et al; 11.2 POJA-L3252 et al; 11.2 POJA-L3255 et al; 11.2 POJA-L3256 et al.
(Neuro)glial cells are specialized supporting cells intimately related to and surround perikarya, axons and dendrites.
See: 11.4 POJA-L3095 et al; 11.5 POJA-L3026 et al; 11.5 POJA-L3031 et al.
Blood vessels are an integral part of the nervous system. All vascular channels are accompagnied by connective tissue elements and cells but delimited from the nervous system sec.
See: 11.5 POJA-L3062 et al; 11.5 POJA-L3043 et al; 11.5 POJA- L4456 et al.
See also: 13 POJA-L4750 Lymphatic and glymphatic system
11.2.1 - images: Peripheral neurons (ganglion cells)
Thoracic neural crest cells migrate in the fifth week along the spinal cord and form segmentally arranged paravertebral ganglia (sympathetic ganglia).These ganglia are connected by longitudinal aligned nerve fibres giving rise to the sympathetic trunks on each side of the vertebral bodies.
See: 11.2.1 POJA-L 3178 et al; 11.2.1. POJA-L 3311 et al; 11.2.1 POJA-L4433 et al.
Unipolar neurons in the spinal ganglia (or dorsal root ganglia) are derived from the neural crest cells as well and carry signals from sensory receptors such as Meissner’s, pacinian corpuscles.
See: 11.2.2 POJA-L2076 et al.
Neural crest cells also migrate to different areas e.g. lungs, heart, digestive tract where autonomic plexuses or terminal (intramural) ganglia are formed close to or within these organs.
See: 11.2.1 POJA-L 3217 et al; 11.2.1. POJA-L3208 et al.
See also general aspect ganglion cells: 11.2.1 POJA-L3186 et al; 11.2.1 POJA-L3194 et al; 11.2.1 POJA-L3292 et al.
11.2.2 - images: Peripheral nerve endings (efferent/afferent)
Dorsal root ganglions contain the cell bodies of unipolar neural crest-derived neurons and their axons are known as afferents. For somatosensory transduction in these sensory neurons ion channels appear to be involved. Pacinian or Meissner’s corpuscules e.g. may encapsulate the nerve ending and show that the distal processes are sensitive to stimulation e.g. vibration or stroking, respectively.
See: 11.2.2 POJA-L 2076 et al; 11.2.2. POJA-L3278 et al; 11.2.2 POJA-L3294 et al; 10.3 POJA-L2037 et al; 10.3 POJA-L2038 et al; 10.3 POJA-L2040 et al; 10.3 POJA-L2274 et al.
11.3 - images: Spinal cord
The spinal cord arises from the neural tube caudal to the 4th pair of somites. The wall of the neural tube is a thick pseudostratified columnar neuro-epithelium, the so-called ventricular zone. In the outer parts of the neuroepithelium a marginal zone develops and becomes the future white matter of the spinal cord as axons grow into it. Several neuroepithelial cells differentiate into neuroblasts and these cells form an intermediate zone (mantle layer) between the ventricular layer and the marginal zone. After the formation of neuroblasts ceases, glioblasts differentiate from the neuroepithelial cells. Eventually the production of neuroblasts and glioblasts ends and the neuroepithelial cells start to differentiate into ependymal cells lining the future central canal of the spinal cord.
See: 11.3 POJA-L3121 et al; 11.5 POA-L3371 et al.
In the adult spinal cord a central mass of gray matter is enclosed with white matter containing myelinated, unmyelinated nerve fibers and numerous neuroglia cells. The gray matter displays a letter H in cross-section indicating an anterior horn and a posterior horn with a central canal.
See: 11.3 POJA-L3121et al; 11.3 POJA-L3122 et al; 11.3 POJA-L3127 et al; 11.3 POJA-L3128 et al; 11.3 POJA-L3130 et al; 11.3 POJ-L3132 et al.
11.4 - images: Cerebellum
The cerebellum and pons derive from the walls of the metencephalon, its cavity is the superior part of the 4th ventricle. Firstly the cerebellar protuberants project into the 4th ventricle and eventually they extend. They fuse in the midline overgrowing partly the 4th ventricle and overlap the pons and medulla.
The adult cerebellum has a cortex (gray matter) of two layers (outer molecular and inner granular layers) and in beween one layer of large neurons (Purkinje cells). The medulla (white matter) contains bands and bundles of nerve fibers, local islets of neurons (e.g. internal nuclei) and abundant neuroglia cells.
See: 11.4 POJA-L2967 et al; 11.4 POJA-L3094 et al; 11.4 POJA-L3108 et al; 11.4 POJA-L4444 et al; 11.4 POJA-L4450 et al; 11.4 POJ-L4451 et al.
11.5 - images: Cerebrum
In the fourth week the cranial part of the neural tube develops into three primary brain vesicles: forebrain (prosencephalon), midbrain (mesencephalon) and hindbrain (rhombencephalon). In the fifth week the forebrain divides into telencephalon and diencephalon while the hindbrain partly divides into metencephalon and myelencephalon. The caudal part of the latter resembles structurally the spinal cord. The neural tube lumen appears as a small central canal.
See: 11.5 POJA-L3371 et al.
The thin roof of the 4th ventricle (part of myelencephalon) is covered by the pia mater that is derived from the mesenchyme. The pia mater (rich in blood vessels) forms together with the ependymal roof the tela choroidea that protrudes into the lumen of the 4th ventricle where it differentiates into the choroid plexus. In the roof of the 3rd ventricle (diencephalon) and in the medial walls of the lateral ventricles (telencephalon) similarly choroid plexuses develop.
See: 11.5 POJA-L3157 et al; 11.5 POJA-L3159 et al; 11.5 POJA-L3160 et al; 11.5 POJA-L3162 et al; 11.5 POJA-L3371 et al.
The adult cerebrum shows in general a cortex (gray matter) of six ill-defined layers of neurons with a great variety in size. The medulla (white matter) contains nerve fiber tracts, local clusters of neurons (e.g. basal ganglia) and numerous neuroglia cells.
See: 11.5 POJA-L2997 et al; 11.5 POJA-L3004 et al; 11.5 POJA-L3363 et al; 11.5 POJA-L4454 et al.
11.6 - images: Pathology
Multiple sclerosis: See: 11.6 POJA-L3866 et al.
Meningoencephalitis: See: 11.6 POJA-L3872 et al.
Alzheimer’s disease. See: 11.6 POJA-L3874 et al.
11.2 - images: Peripheral nervous tissue
Peripheral nerves are formed by bundles of nerve fibers which originate from neurons in the gray matter of the spinal cord (anterior horns) and in the spinal ganglia (aggregations of neurons outside the central nervous system).
See: 11.2 POJA-L3226 et al; 11.2 POJA-L3243 et al; 11.2.1 POJA-L3178 et al; 11.3 POJA-L3132 et al.
The peripheral nerve is composed of long nerve cell processes and contain myelinated and non-myelinated nerve fibers.
A peripheral myelinated nerve fiber is an axon enclosed by a continuous basal lamina (or external lamina). The fiber is subdivided in internodi which are linked together and each internodus is governed by one Schwann cell.
See: 11.2 POJA-L3231 et al; 11.2 POJA-L3249 et al; 11.2 POJA-L3252 et al.
Each nerve cell possess a nucleus surrounded by the cytoplasm (perikaryon). The nerve cell with its processes (axon and dendrites) forms a neuron which is the functional and anatomical unit of the nervous system. The axon conducts signals over considerable distances. The dendrites are branching elaborate extensions of the perikaryon and collect or receive impulses.
See: 11.2 POJA-L3275 et al; 11.5 POJA-L3019 et al; 11.5 POJA-L3071 et al.
Synapses are membranous contact points between the neurons where e.g. an axon of one neuron touch the cell membrane of another neuron.
See: 11.2.1 POJA-L3311 et al; 11.3 POJA-L3141 et al; 11.5 POJA-L3079 et al.
A large number of the processes are enveloped by a phospholipid sheath, the myelin sheath which is white in living tissue. Hence the name white matter in the central nervous system versus the gray matter that is composed of aggregations of neurons.
See: 11.2 POJA-L2937 et al; 11.2 POJA-L3249 et al; 11.2 POJA-L3252 et al; 11.2 POJA-L3255 et al; 11.2 POJA-L3256 et al.
(Neuro)glial cells are specialized supporting cells intimately related to and surround perikarya, axons and dendrites.
See: 11.4 POJA-L3095 et al; 11.5 POJA-L3026 et al; 11.5 POJA-L3031 et al.
Blood vessels are an integral part of the nervous system. All vascular channels are accompagnied by connective tissue elements and cells but delimited from the nervous system sec.
See: 11.5 POJA-L3062 et al; 11.5 POJA-L3043 et al; 11.5 POJA- L4456 et al.
See also: 13 POJA-L4750 Lymphatic and glymphatic system
11.2.1 - images: Peripheral neurons (ganglion cells)
Thoracic neural crest cells migrate in the fifth week along the spinal cord and form segmentally arranged paravertebral ganglia (sympathetic ganglia).These ganglia are connected by longitudinal aligned nerve fibres giving rise to the sympathetic trunks on each side of the vertebral bodies.
See: 11.2.1 POJA-L 3178 et al; 11.2.1. POJA-L 3311 et al; 11.2.1 POJA-L4433 et al.
Unipolar neurons in the spinal ganglia (or dorsal root ganglia) are derived from the neural crest cells as well and carry signals from sensory receptors such as Meissner’s, pacinian corpuscles.
See: 11.2.2 POJA-L2076 et al.
Neural crest cells also migrate to different areas e.g. lungs, heart, digestive tract where autonomic plexuses or terminal (intramural) ganglia are formed close to or within these organs.
See: 11.2.1 POJA-L 3217 et al; 11.2.1. POJA-L3208 et al.
See also general aspect ganglion cells: 11.2.1 POJA-L3186 et al; 11.2.1 POJA-L3194 et al; 11.2.1 POJA-L3292 et al.
11.2.2 - images: Peripheral nerve endings (efferent/afferent)
Dorsal root ganglions contain the cell bodies of unipolar neural crest-derived neurons and their axons are known as afferents. For somatosensory transduction in these sensory neurons ion channels appear to be involved. Pacinian or Meissner’s corpuscules e.g. may encapsulate the nerve ending and show that the distal processes are sensitive to stimulation e.g. vibration or stroking, respectively.
See: 11.2.2 POJA-L 2076 et al; 11.2.2. POJA-L3278 et al; 11.2.2 POJA-L3294 et al; 10.3 POJA-L2037 et al; 10.3 POJA-L2038 et al; 10.3 POJA-L2040 et al; 10.3 POJA-L2274 et al.
11.3 - images: Spinal cord
The spinal cord arises from the neural tube caudal to the 4th pair of somites. The wall of the neural tube is a thick pseudostratified columnar neuro-epithelium, the so-called ventricular zone. In the outer parts of the neuroepithelium a marginal zone develops and becomes the future white matter of the spinal cord as axons grow into it. Several neuroepithelial cells differentiate into neuroblasts and these cells form an intermediate zone (mantle layer) between the ventricular layer and the marginal zone. After the formation of neuroblasts ceases, glioblasts differentiate from the neuroepithelial cells. Eventually the production of neuroblasts and glioblasts ends and the neuroepithelial cells start to differentiate into ependymal cells lining the future central canal of the spinal cord.
See: 11.3 POJA-L3121 et al; 11.5 POA-L3371 et al.
In the adult spinal cord a central mass of gray matter is enclosed with white matter containing myelinated, unmyelinated nerve fibers and numerous neuroglia cells. The gray matter displays a letter H in cross-section indicating an anterior horn and a posterior horn with a central canal.
See: 11.3 POJA-L3121et al; 11.3 POJA-L3122 et al; 11.3 POJA-L3127 et al; 11.3 POJA-L3128 et al; 11.3 POJA-L3130 et al; 11.3 POJ-L3132 et al.
11.4 - images: Cerebellum
The cerebellum and pons derive from the walls of the metencephalon, its cavity is the superior part of the 4th ventricle. Firstly the cerebellar protuberants project into the 4th ventricle and eventually they extend. They fuse in the midline overgrowing partly the 4th ventricle and overlap the pons and medulla.
The adult cerebellum has a cortex (gray matter) of two layers (outer molecular and inner granular layers) and in beween one layer of large neurons (Purkinje cells). The medulla (white matter) contains bands and bundles of nerve fibers, local islets of neurons (e.g. internal nuclei) and abundant neuroglia cells.
See: 11.4 POJA-L2967 et al; 11.4 POJA-L3094 et al; 11.4 POJA-L3108 et al; 11.4 POJA-L4444 et al; 11.4 POJA-L4450 et al; 11.4 POJ-L4451 et al.
11.5 - images: Cerebrum
In the fourth week the cranial part of the neural tube develops into three primary brain vesicles: forebrain (prosencephalon), midbrain (mesencephalon) and hindbrain (rhombencephalon). In the fifth week the forebrain divides into telencephalon and diencephalon while the hindbrain partly divides into metencephalon and myelencephalon. The caudal part of the latter resembles structurally the spinal cord. The neural tube lumen appears as a small central canal.
See: 11.5 POJA-L3371 et al.
The thin roof of the 4th ventricle (part of myelencephalon) is covered by the pia mater that is derived from the mesenchyme. The pia mater (rich in blood vessels) forms together with the ependymal roof the tela choroidea that protrudes into the lumen of the 4th ventricle where it differentiates into the choroid plexus. In the roof of the 3rd ventricle (diencephalon) and in the medial walls of the lateral ventricles (telencephalon) similarly choroid plexuses develop.
See: 11.5 POJA-L3157 et al; 11.5 POJA-L3159 et al; 11.5 POJA-L3160 et al; 11.5 POJA-L3162 et al; 11.5 POJA-L3371 et al.
The adult cerebrum shows in general a cortex (gray matter) of six ill-defined layers of neurons with a great variety in size. The medulla (white matter) contains nerve fiber tracts, local clusters of neurons (e.g. basal ganglia) and numerous neuroglia cells.
See: 11.5 POJA-L2997 et al; 11.5 POJA-L3004 et al; 11.5 POJA-L3363 et al; 11.5 POJA-L4454 et al.
11.6 - images: Pathology
Multiple sclerosis: See: 11.6 POJA-L3866 et al.
Meningoencephalitis: See: 11.6 POJA-L3872 et al.
Alzheimer’s disease. See: 11.6 POJA-L3874 et al.
COPYRIGHTS
All rights reserves worldwide for the POJA collection are hold by L.G. Poels and P.H.K. Jap and Radboud University Medical Center (Radboud UMC Nijmegen). No one may modify, copy, distribute, transmit, display, or publish any materials contained in the POJA collection without prior written permission of the authors Poels and Jap or the UMC St Radboud. Any commercial use of the POJA collection is forbidden. POJA images are partly deposited in the Health Education Assets Library (HEAL database) as well as in the MedEdPortal/AAMC database).
All rights reserves worldwide for the POJA collection are hold by L.G. Poels and P.H.K. Jap and Radboud University Medical Center (Radboud UMC Nijmegen). No one may modify, copy, distribute, transmit, display, or publish any materials contained in the POJA collection without prior written permission of the authors Poels and Jap or the UMC St Radboud. Any commercial use of the POJA collection is forbidden. POJA images are partly deposited in the Health Education Assets Library (HEAL database) as well as in the MedEdPortal/AAMC database).