DOCSLIB.ORG

Nervous-System.Pdf

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Nervous-System.Pdf NERVOUS TISSUE • The nervous sys. is classified into: • Central nervous system (C.N.S): brain and spinal cord. • Peripheral nervous system (P.N.S): a) Peripheral nerves Cranial Spinal b) Ganglia Cerebro–spinal Autonomic Sympathetic Parasympathetic ParasympatheticParasympathetic THETHE NEURONNEURON Definition: • Is the structural and functional unit of the nervous tissue. Structure: • The neuron or the nerve cell consists of: • Cell body • It contains the nucleus and surrounding cytoplasm. • Processes: axon and dendrites. (1) THE CELL BODY: • The Cell membrane: very thin. • The nucleus: Large, rounded, central and (open – face type) with a prominent nucleolus. TheThe cytoplasm:cytoplasm: •Nissl granules •Neurofibrils •Golgi apparatus •Mitochondria (1) THE CELL BODY: • Inclusions • Melanin pigments • Lipofuscin pigments: • Glycogen granules • Fat droplets. Centrosomes • Are absent in • mature nerve • cells as they • can not divide. • Are present in • young nerve • cells of certain • vertebrates. The axon The dendrites Number: Single. Multiple. Thickness Thin & Thick & and Length: long. short. Diameter: It has a constant Their diameter decrease diameter along its gradually towards their length. ends i.e. tapering. Contour: Smooth. Irregular. The axon The dendrites Branch. It branches at its They give extensive terminal end only i.e. branching along their “terminal arborization” course. The branches but it may give collateral branches which arise at arise at acute angles and right angles. may show spines. Conte Contains Contain neurofibrils and :nt mitochondria and Nissl granules. neurofibrils The axon The dendrites Conductio carries impulses away carry the impulses to the n of nerve impulses : from the cell body cell body) centrifugal conduction Centripetal conduction ClassificationClassification ofof thethe neuronsneurons (nerve(nerve cells)cells) According to the number of processes (Polarity): Unipolar nerve cells: Nerve cells are rounded with only one process. Site: mesencephalic nucleus of the trigeminal nerve. Pseudounipolar nerve cells: Nerve cells are rounded. These cells are at first bipolar, but as development proceeds the two processes of the cell meet at one side of the body forming a single process which divides in inverted T- shaped manner into 2 branches, a dendrite and an axon. The single process of each cell is convoluted at its beginning in the nerve cell forming a glomerulus in its cytoplasm. Site: spinal ganglia. • Bipolar nerve cells: • The cells are fusiform or spindle-shaped, with 2 processes, a dendrite and an axon. • Site: Retina of the eye. • Spiral ganglia and vestibular ganglia in the ear. • Olfactory epithelium of the nose. • Multipolar nerve cells: • Have many dendrites and one axon. • Polygonal or stellate shaped: star-shaped. • Site: - Sympathetic ganglia. • - Anterior horn cells of the spinal cord. • Pyramidal: • Site: cerebral cortex. • Pyriform: flask –shaped cells. • Site: Purkinje cells of the cerebellum. THE NERVE FIBER • Definition: It is the axon of a nerve cell. • The axon may be naked or ,with myelin sheath ( ensheathed )or both neurolemma. • The axon (Axis Cylinder) • Structure : • The axon is surrounded by a membrane called “axolemma” and its cytoplasm is known as “axoplasm”. It contains neurofilaments, neurotubules and mitochondria but no Nissl granules. • Length: • May be very long (Golgi type I) or • very short (Golgi type II). • Diameter: - thick … conducting impulses rapidly - Thin….. conducting impulses slowly. The myelin Sheath Histological appearance: • It is a white tubular covering for the axon. • It is interrupted at intervals by constrictions called “nodes of Ranvier”. The segment between two successive nodes is called “internodal segment”. Chemical Structure: • It is a lipoprotein sheath • It appears in the form of concentric layers derived mainly from the lipid middle layer of the cell membrane of Schwann cell Staining: • In H & E preparation: the fat of myelin dissolves in fat solvent (xylol) and appears as an empty space. • It is stained black by osmic acid. Function: Insulation of the nerve impulses. The Neurolemmal Sheath (Schwann Cells) • Histological appearance: • It is formed of a chain of cells forming a tube around myelin sheath. • Each Schwann cell has a flat oval nucleus and corresponds to an internodal segment. • The cells come in contact with the axon at the nodes of Ranvier. • Function: -Insulation of nerve impulses in nonmyelinated nerve fibers. -Important role in regeneration of peripheral nerve after injury. (No regeneration of nerve fibers occurs in the CNS where the fibers are myelinated without neurolemma). Types of Nerve Fibers: Naked Fibers: (non myelinated without neurolemma) e.g. - Termination of peripheral nerves. - Fibers in the gray matter. Ensheathed Fibers: -Myelinated with neurolemma: • e.g. peripheral nerves. -Myelinated without neurolemma: • e. g. nerve fibers in the white • matter and optic nerve. -Non- myelinated with neurolemma: • e.g. sympathetic nerve fibers. StructureStructure ofof aa peripheralperipheral NerveNerve Trunk:Trunk: Nervous component: Groups of nerve fibers (myelinated axons with neurolemma) arranged in bundles. -In Hx. & E. stained section: Each fiber shows a centrally stained acidophilic axon, surrounded by an empty space of the dissolved myelin and a thin outer pink rim of The nuclei of these .cell cytoplasm Schwann .cells may be seen if they are cut in the section -In osmic acid stained section: The myelin sheath of the nerve fibers appears .as rounded black circles C. T. component: -Epineurium : It is a dense C. T., which surrounds the whole nerve trunk. -Perineurium: It is a dense C. T., which surrounds the bundles of nerve fibers. -Endoneurium: (Henle’s sheath) It is a delicate loose C. T. between the individual nerve GANGLIAGANGLIA •Definition: • A nerve ganglion is a collection of nerve cells and nerve fibers, covered by a C. T. capsule, outside the C. N. S. • NB: a collection of nerve cells inside the C. N. S is called nucleus. Spinal Sympathetic ganglion ganglion Site : C.T. Capsul. Spinal Sympathetic ganglion Nerve cells: ganglion Type: Size: Arrangement: Number: Nuclei: Satellite Cs Glomerulus : Spinal Sympathetic ganglion Nerve ganglionThickly myelinated. Thinly or non myelinated Fiber Widely separated from each Close to each other. other .Irregularly distributed s Parallel to the capsule. Present Synapse absent Synapse: (as the fibers fibers preganglionic) are the peripheral synapse with the ganglion processes of the nerve cells whose axons form cells whose axons enter . )the postganglionic fibers the C.N.S) Spinal Sympathetic ganglion Blood supply: ganglion Function: Acts as relay for Acts as relay for different different motor sensations functions arising before their from the spinal cord. entrance into the spinal cord. Nervous tissue PracticalPractical SlidesSlides .
Load more

Recommended publications
  • 1365.Full.Pdf
    The Journal of Neuroscience May 1966, 6(5): 1365-1371 Analysis of the Carbohydrate Composition of Axonally Transported Glycoconjugates in Sciatic Nerve Clyde E. Hart and John G. Wood Department of Anatomy, Emory University School of Medicine, Atlanta, Georgia 30322 Glycosidase enzyme digestion in combination with postembed- schlag and Stone, 1982, for reviews). Therefore, the ability to ding lectin cytochemistry was used to study the carbohydrate characterize in situ the carbohydrate compositionof lectin bind- composition of axonally transported glycoproteins. A cold block ing sites of intracellular membranecompartments and on the procedure for the interruption of axonal transport was employed cell surface may further our understandingof the site(s) of gly- to increase selectively the population of anterograde moving coprotein oligosaccharideprocessing in neurons. components on the proximal side of the transport block. Elec- tron-microscopic observations revealed that a cold block applied In this study we have used a modification of the cold block to the sciatic nerve of an anesthetized rat produced an increase technique of Hanson (1978) to interrupt axonal transport in the in axonal smooth membrane vesicles at a site directly proximal sciatic nerve of rats in order to increase the content of antero- to the cold block. Postembedding lectin cytochemistry of the gradely transported glycoproteins at a focal point along the nerve. sciatic nerve demonstrated a substantial increase in concanav- Results of postembedding lectin cytochemistry and endo- and alin A (Con A), wheat germ agglutinin (WGA), and succinylat- exo-glycosidase digestions of the cold-blocked sciatic nerve in- ed WGA binding sites in axons directly proximal to the cold dicated that some of the axonally transported glycoprotein car- block.
    [Show full text]
  • Nomina Histologica Veterinaria, First Edition
    NOMINA HISTOLOGICA VETERINARIA Submitted by the International Committee on Veterinary Histological Nomenclature (ICVHN) to the World Association of Veterinary Anatomists Published on the website of the World Association of Veterinary Anatomists www.wava-amav.org 2017 CONTENTS Introduction i Principles of term construction in N.H.V. iii Cytologia – Cytology 1 Textus epithelialis – Epithelial tissue 10 Textus connectivus – Connective tissue 13 Sanguis et Lympha – Blood and Lymph 17 Textus muscularis – Muscle tissue 19 Textus nervosus – Nerve tissue 20 Splanchnologia – Viscera 23 Systema digestorium – Digestive system 24 Systema respiratorium – Respiratory system 32 Systema urinarium – Urinary system 35 Organa genitalia masculina – Male genital system 38 Organa genitalia feminina – Female genital system 42 Systema endocrinum – Endocrine system 45 Systema cardiovasculare et lymphaticum [Angiologia] – Cardiovascular and lymphatic system 47 Systema nervosum – Nervous system 52 Receptores sensorii et Organa sensuum – Sensory receptors and Sense organs 58 Integumentum – Integument 64 INTRODUCTION The preparations leading to the publication of the present first edition of the Nomina Histologica Veterinaria has a long history spanning more than 50 years. Under the auspices of the World Association of Veterinary Anatomists (W.A.V.A.), the International Committee on Veterinary Anatomical Nomenclature (I.C.V.A.N.) appointed in Giessen, 1965, a Subcommittee on Histology and Embryology which started a working relation with the Subcommittee on Histology of the former International Anatomical Nomenclature Committee. In Mexico City, 1971, this Subcommittee presented a document entitled Nomina Histologica Veterinaria: A Working Draft as a basis for the continued work of the newly-appointed Subcommittee on Histological Nomenclature. This resulted in the editing of the Nomina Histologica Veterinaria: A Working Draft II (Toulouse, 1974), followed by preparations for publication of a Nomina Histologica Veterinaria.
    [Show full text]
  • The Ultrastructure of Schmidt-Lanterman Clefts and Related Shearing Defects of the Myelin Sheath by J
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by PubMed Central The Ultrastructure of Schmidt-Lanterman Clefts and Related Shearing Defects of the Myelin Sheath BY J. DAVID ROBERTSON, M.D. (From the Department of Anatomy, University College, London) PLATes 14 To 17 (Received for publication, August 7, 1957) ABSTRACT Schmidt-Lanterman clefts in frog sciatic nerves have been studied in thin sections by electron microscopy utilizing permanganate fixation and araldite em- bedding. It is shown that they are shearing defects in myelin in which the lamellac are separated widely at the major dense lines. Each lamella consisting of two apposed Schwann cell unit membranes ~-~ 75 A across traverses the cleft intact. The unit membranes composing each lameUa sometimes are slightly (~-~ $0 to 100 A) separated in the clefts. The layers between the lamellae contain mem- branous structures which may be components of the endoplasmic reticulum. These layers are continuous with the outer layer of Schwann cytoplasm and the thin and inconstant cytoplasmic layer next to the axon (Mauthner's sheath). Each of these layers in perfect clefts constitutes a long helical pathway through the myelin from the axon. One of these is connected with Schwann cytoplasm and the other directly with the outside. A type of cross-sectional shearing defect, not h/therto recognized, is described and shown to be a kind of Schmidt-Lanterman cleft. Incomplete clefts are seen and interpreted as representing stages in a dynamic process whereby the myelin lamellae may be constantly separating and coming together again in life.
    [Show full text]
  • Small Basic Proteins of Myelin from Central and Peripheral Nervous Systems Are Encoded by the Same Gene (Cdna Cloning/Mrna Levels/Oligodendrocytes/Schwann Cells) A
    Proc. Nati. Acad. Sci. USA Vol. 83, pp. 1111-1114, February 1986 Neurobiology Small basic proteins of myelin from central and peripheral nervous systems are encoded by the same gene (cDNA cloning/mRNA levels/oligodendrocytes/Schwann cells) A. MENTABERRY, M. ADESNIK, M. ATCHISON*, E. M. NORGARD, F. ALVAREZ, D. D. SABATINI, AND D. R. COLMANt Department of Cell Biology, New York University School of Medicine, 550 First Avenue, New York, NY 10016 Contributed by D. D. Sabatini, September 13, 1985 ABSTRACT Peripheral nervous system (PNS) and central kDa, respectively) represent =90% of the total complement nervous system (CNS) rodent myelins, which are produced by of MBPs and have the same amino acid sequence, except for different cell types, share common morphological and func- an internal deletion of 40 amino acids near the carboxyl tional characteristics although their major integral membrane terminus of S (3). The two other species (21.5 kDa and 17 proteins are completely different. Both types of myelin how- kDa) differ from the L and S proteins only in that they contain ever, contain sets of four myelin basic proteins (MBPs), which near their amino termini an additional polypeptide segment share similar immunochemical and electrophoretic properties. that is common to both (4). It has been shown that the CNS We have isolated and characterized cDNA clones correspond- MBPs represent four distinct primary translation products, ing to the rat mRNAs encoding the small MBPs (SMBPs) found and from this it was inferred that they are encoded by four in both CNS and PNS myelin. Sequence analysis of these clones distinct mRNAs (5, 6).
    [Show full text]
  • Arxiv:1708.00534V1 [Q-Bio.NC] 1 Aug 2017 Myelin and Saltatory Conduction
    Myelin and saltatory conduction Maurizio De Pitt`a The University of Chicago, USA EPI BEAGLE, INRIA Rhˆone-Alpes, France August 3, 2017 (Submitted as contributed section to the chapter on “Neurophysiology” of the book “Da˜no cerebral” (Brain damage), JC Arango-Asprilla & L Olabarrieta-Landa eds., Manual Moderno Editions.) arXiv:1708.00534v1 [q-bio.NC] 1 Aug 2017 1 Myelin allows fast and reliable conduction of nerve pulses Myelin is a fatty substance that ensheathes the axon of some nerve cells, forming an electrically insulating layer. It is considered a defining characteristic of jawed vertebrates and is essential for the proper functioning of the nervous system of these latter. Myelin is made by different cell types, and varies in chemical composition and configuration, but performs the same insulating function. Myelinated axons look like strings of sausages under a microscope, and because of their white appearance they are integral components of the “white matter” of the brain. The myelin sausages ensue from wrapping of axons by myelin in multiple, concentric layers and are separated from each others by small unmyelinated axonal segments known as nodes of Ranvier. Typically the length of a node is very small (0.1%) compared to the length of the myelinated segment. Single myelinated fibers range in diameter from 0.2 to 20 µm on average, while unmyelinated fibers range between 0.1 and 1 µm [1]. Peripheral axons are myelinated only if their diameter is larger than about 1 µm, and the axonal caliber maintains a rather constant ratio to the myelin sheath thickness [2]. A normal myelin ensheathing of a mature peripheral nerve is usually 100 times as long as the diameter of the corresponding axon [3].
    [Show full text]
  • Epithelial Tissue (Epithelium)
    Epithelial tissue (epithelium) General characteristics of epithelium Is avascular tissue (without blood supply – cells receive nourishment by diffusion from a highly vascular area of loose connective tissue just below the basement membrane called the lamina propria ) is highly cellular tissue – cells are arranged to form cohesive sheet or groups with no or little extracellular matrix displays a free surface – usualy luminal surface (turned to the lumen) opposite (basal) surface adheres to extracellular basement membrane or lamina basalis epithelial cells display polarity – apical (luminal), lateral and basal surfaces with structural specialization epithelial cells are specialised for absorption, secretion or to act as barrier lateral surfaces display junctional complexes for intercellular cohesion and communication One type of epithelium may change into another type – metaplasia (examples: pseudostratified ep. of respiratory passages transforms into stratified squamous ep. on the surface of epiglottis and soft palate) Membrane specializations of epithelia Lateral surface Specialised structures are present in epithelia which link individual cells together. Two main adhesion types are distinguished: 1. Cell membrane proteins acting as specialised cell adhesion molecules (CAMs) 2. Specialised areas of the cell membrane incorporated into cell junctions. Three types are recognized: occluding junctions, anchoring or adherence junctions and communicating junctions. o Occluding junctions bind cell together to form an impermeable barrier . Zonula occludens or tight junction o Anchoring junctions link the cytoskeleton of cells to each other and two underlying tissues . Zonula adherens provides mechanical strength . Macula adherens or desmosomes provides mechanical strength in tissues where there are tensile or shearing stresses, eg skin o Communications junctions allow direct cell-cell communication .
    [Show full text]
  • Selective and Controlled Myelin Formation by Individual Interfascicular
    bioRxiv preprint doi: https://doi.org/10.1101/2020.02.20.957522; this version posted February 20, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. Original Research Article Selective and controlled myelin formation by individual interfascicular oligodendrocytes in the mouse corpus callosum Running title: Selective myelination of callosal oligodendrocytes Tatsuhide Tanaka1,7*, Nobuhiko Ohno2,7, Yasuyuki Osanai3, 4, Sei Saitoh5, 6, Truc Quynh Thai2, Kazuya Nishimura1, Takeaki Shinjo1, Shoko Takemura1, Kouko Tatsumi1 and Akio Wanaka1 1Department of Anatomy and Neuroscience, Nara Medical University, Kashihara, Nara, Japan 2Department of Anatomy, Division of Histology and Cell Biology, Jichi Medical University, School of Medicine, Shimotsuke, Tochigi, Japan 3Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia 4Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, Okazaki, Aichi, Japan 5Section of Electron Microscopy, Supportive Center for Brain Research, National Institute for Physiological Sciences, Okazaki, Aichi, Japan 6Department of Anatomy II and Cell Biology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan 7These authors contributed equally to this work 1 bioRxiv preprint doi: https://doi.org/10.1101/2020.02.20.957522; this version posted February 20, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. Acknowledgements We thank Mrs. Atsuko Imai (National Institute for Physiological Sciences), Dr. Mariko Yamano (Nara Medical University), Dr. Yuki Terada (Nara Medical University), Dr. Ayami Isonishi (Nara Medical University), Dr. Yoshio Bando (Akita University), Mrs.
    [Show full text]
  • NERVE TISSUE Neuron – Nerve Cell
    Department of Histology and Embryology, P. J. Šafárik University, Medical Faculty, Košice NERVE TISSUE: Sylabus for foreign students Author: doc. MVDr. Iveta Domoráková, PhD. Revised by: prof. MUDr. Eva Mechírová, CSc. NERVE TISSUE FUNCTION: Reception, transmission, processing of nerve stimuli. Coordination of all functional activities in the body: - motor function (body movement) - sensory (rapid response to external stimuli) - visceral, endocrine and exocrine glands - mental functions, memory, emotion A) Anatomically nervous system consists of: 1. CNS (central nervous system) – brain, spinal cord 2. PNS (peripheral nervous system) – peripheral nerves and ganglia B) Functionally nervous system is divided into the: 1. Somatic nervous system (sensory and motor innervation) 2. Autonomic nervous system (involuntary innervation of smooth muscles, glands) C) Microscopic structure of the nerve tissue - two types of cells: 1. Nerve cells – neurons 2. Glial cells (supporting, electrical insulation, metabolic function) Neuron – nerve cell - is the structural and functional unit of the nerve tissue - receives stimuli from other cells - conducts electrical impulses to another cells by their processes - chainlike communication - ten bilion of neurons in humans A. Neurons according the shape: Pyramidal (E) star-shaped (D) pear-shaped (G) oval (B) B. Types of neurons according number of the processes 1. multipolar (D,E,G)) 2. bipolar (A) 3. pseudounipolar (B) 4. unipolar C. Neurons - according the function Motor (efferent) neurons – convey impulses
    [Show full text]
  • Nervous Tissue
    Nervous Tissue Dr. Heba Kalbouneh Associate Professor of Anatomy and Histology Nervous Tissue • Controls and integrates all body activities within limits that maintain life • Three basic functions 1. sensing changes with sensory receptors 2. interpreting and remembering those changes 3. reacting to those changes with effectors (motor function) 2 The PNS is divided into : 1- Somatic nervous system (SNS) 2- Autonomic nervous system (ANS) Sensory (Afferent) vs. Motor (Efferent) sensory (afferent) nerve (pseudo-) unipolar neurons conducting impulses e.g., skin from sensory organs to the CNS motor (efferent) nerve e.g., muscle multipolar neurons conducting impulses from the CNS to effector organs (muscles & glands) Gray’s Anatomy 38 1999 Organization Sensory Integration Motor SNS SNS (Sensory) (Motor) Brain Spinal ANS ANS cord (Motor) (Sensory) 6 Neuron has three parts: (1) a cell body: perikaryon or soma (2) dendrites (3) an axon Neurons • Dendrites: carry nerve impulses toward cell body • Axon: carries impulses away from cell body • Synapses: site of communication between neurons using chemical neurotransmitters • Myelin & myelin sheath: lipoprotein covering produced by glial cells (e.g., Schwann cells in PNS, oligodendrocytes in the CNS) that increases axonal conduction velocity dendrites cell axon with body myelin sheath Schwann cell synapses Moore’s COA5 2006 Notice that action potential propagation is unidirectional 9 Neurons 1. Cell body a) Nissl bodies b) Golgi apparatus c) Neurofilaments (IFs) d) Microtubules e) Lipofuscin pigment
    [Show full text]
  • Nerve & Muscle. Divisions of Nervous System
    INTRODUCTION OF EXCITATORY TISSUES By Dr. Mudassar Ali Roomi (MBBS, M.Phil.) Assistant Professor Physiology RED CNS BLUE PNS Divisions of nervous system: CNS & PNS Central nervous system (CNS): • Brain (in skull) & Spinal cord (in vertebral canal): Divided into gray matter & white matter. • Formed by neurons & supporting cells (neuroglia) • Gray matter: nerve cell bodies, proximal parts of axons & dendrites. • White matter: nerve fibers / axons. Major parts of Brain: 1. Prosencephalon: Forebrain: (cerebral hemispheres, thalamus, hypothalamus). 2. Mesencephalon: Midbrain 3. Rhombencephalon: Hindbrain: (Pons, cerebellum, medulla oblongata) Brain stem: Midbrain, Pons, Medulla oblongata. Peripheral nervous system (PNS) • Formed by neurons & their processes outside CNS. • Cranial nerves (from brain) • Spinal nerves (from spinal cord) • 2 divisions of PNS: SOMATIC / VOLUNTARY NERVOUS SYSTEM: Nerves supplying skeletal muscles Controls movements of body by acting on skeletal muscles. AUTONOMIC / VISCERAL / VEGETATIVE/ INVOLUNTARY NERVOUS SYSTEM: Function: Controls viscera 2 sub-divisions: SYMPATHETIC PARASYMPATHETIC Cells of nervous tissue TWO TYPES OF CELLS ARE PRESENT IN THE NERVOUS TISSUE: • Nerve cells or Neurons: which are excitable and conduct electrical impulses • Glial (neuroglial) cells or supporting cells: which support, nurture, and protect the neurons. 18 November 2013 6 The Neuron • Structural and functional unit of nervous system. • Features: – Nucleus & cytoplasmic organelles. – No centrosome cannot divide. – Branches Axon / nerve fiber & Dendrites. 18 November 2013 7 Nerve cell body (perikaryon or soma) • It contains nucleus, cytoplasmic organelles, inclusions and cytoskeletal components. • Nucleus: it is large spherical and pale staining (vesicular) and centrally placed in most of the cases. It contains abundant euchromatin (chromatin is finely dispersed) and a large nucleolus (owl-eye nucleus).
    [Show full text]
  • Age Changes in Internodal Length in the Human Spinal Roots* -Nerve Teasing Study
    Nagoya J. med. Sci. 36: 17-27, 1973 AGE CHANGES IN INTERNODAL LENGTH IN THE HUMAN SPINAL ROOTS* -NERVE TEASING STUDY- MASAKUNI MUKOYAMA 1st Department of Internal Medicine, Nagoya University School of Medicine (Director: Associate Prof. ltsuro Sobue) INTRODUCTION Various investigators have made quantitative histologic measurements for demonstrating pathologic alteration of peripheral neuropathies. There are two popular methods that have been used for a long time-counting nerve fibers in a unit intrafascicular area and determining distribution of fiber diameters. They are subsequently referred as fiber population and fiber spectrum 1)2) 3}i) 5) • The measurement of distances between the nodes of Ranvier of teased nerve fibers has recently been recognized as another useful procedure for investigating pathogenesis of peripheral nerve disorders 6)7) 8) 9). However, there has hitherto been no report on teasing study of the spinal roots. The anterior and posterior roots have different functions: the former is concerned with motor function and the latter with sensory. Specific pathologic alterations might be found in either root or both in certain disorders of the peripheral nerves, because clinically some peripheral neuropathies only show motor dysfunction, whereas others show sensory, or both. For demonstrating the degrees of abnormality in these cases, it becomes necessary to determine the normal variations in subjects of all age ranges. The purpose of this study is to establish the age changes, as a number, in internodal length of the anterior and posterior roots in normal subjects. The anterior and posterior roots of the fifth lumbar segment were chosen for this study. This segment innervates the peripheral parts of the legs.
    [Show full text]
  • Node of Ranvier, Functions & Functional Anatomy
    AMMAR YASEEN MANSOUR Node of Ranvier, Functions & Functional Anatomy " Innovated Conception" The anatomy of node of Ranvier is well illustrated. However, the function of each anatomical detail of its structure (i.e. the functional anatomy) still reserve its secret until now. Here after, I will try to find out the actual functions and the functional anatomy of node of Ranvier. The concerned anatomical details are: 1. The Gated Sodium Ion Channels that are massively present in the cell membrane at node of Ranvier. 2. The Myelin Sheath that is absent at node of Ranvier. 3. The Diameter of Neural Fiber, which loses about third of its value at node of Ranvier. 4. Finally, the Microtubules & Microfilaments that are massively present in the cytoplasm of node of Ranvier; figure (1). Figure (1) Node of Ranvier, is only present in the myelinated neural fiber. The segments of the neural fiber between two subsequent nodes are the internodal sgments. The internodal segments are covered with the myelin sheath. However, at nodes of Ranvier, the neural fiber losses its myelin sheath. At nodes of Ranvier, the cell membrane is rich of sodium ion channels. At nodes of Ranvier, the neural fiber losses third of its diameter. At nodes of Ranvier, the cell membrane is massively supported with the microtubules and the microfilamens. 1- Nodes of Ranvier, The Power Stations Upon its passage through each node of Ranvier, the tail of action pressure wave is going to be positively charged by the incoming sodium ions. The pressure gated sodium ion channels facilitate the entry of sodium ions Na+ into the neural fiber.
    [Show full text]