histologic structure of nervous system

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histologic nervous system, neuron, neuroglial, axon, dendrite, brain, spinal cord, blood-brain barrier

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histologic structure of nervous system

  1. 1. HISTOLOGY OF NERVOUS SYSTEM DR. I WAYAN SUGIRITAMA,M.Kes HISTOLOGY DEPARTMENT MEDICAL FACULTY OF UDAYANA UNIVERSITY
  2. 2. NERVOUS SYSTEM <ul><li>The most complex system in the human body </li></ul><ul><li>Formed by network more than 100 million neuron </li></ul><ul><li>Each neuron has a thousand interconnection  a very complex system for communication </li></ul><ul><li>Nerve tissue is distribute throughout the body, anatomically divide into : CNS & PNS </li></ul><ul><li>Structurally consist : nerve cells & glial cells </li></ul>23/06/09
  3. 3. CONTENTS <ul><li>Cells of nervous system </li></ul><ul><li>Synaptic communication </li></ul><ul><li>Central nervous system & Peripheral nervous system & associated structure </li></ul><ul><li>Regeneration of nervous system </li></ul>23/06/09
  4. 4. REFFERENCES <ul><li>Color Textbook Histology, third edition, leslie P. Gartner </li></ul><ul><li>Basic Histology, tenth edition, L. Carlos Junqueira,2003 </li></ul><ul><li>Histology and Cell Biology, second edition,2007 </li></ul><ul><li>Elsevier’s Integrated Histology,2007 </li></ul>23/06/09
  5. 5. CELLS OF NERVOUS SYSTEM 23/06/09 NEURON NEUROGLIA
  6. 6. STRUCTURE OF NEUR ON <ul><li>Principle cells of Nervous Tissue </li></ul><ul><li>Consist of 3 parts : </li></ul><ul><ul><li>CELL BODY (perikaryon/soma) </li></ul></ul><ul><ul><li>A single AXON </li></ul></ul><ul><ul><li>Multiple DENDRITES </li></ul></ul><ul><li>ø 5-150 µm </li></ul>23/06/09
  7. 7. CELL BODY (PERIKARYON) <ul><li>Central portion of the cell </li></ul><ul><li>Generally are polygonal </li></ul><ul><li>Different shape and size  characteristic regions of nervous system </li></ul><ul><li>Contain : </li></ul><ul><ul><li>Nucleus </li></ul></ul><ul><ul><li>Perinuclear cytoplasm </li></ul></ul>23/06/09
  8. 8. ULTRASTRUCTURE OF NEURON <ul><li>Nucle us : </li></ul><ul><li>large, spherical to ovoid and centraly located </li></ul><ul><li>a single prominent nucleolus </li></ul><ul><li>finely dispersed chromatin </li></ul><ul><li> trancriptionaly active </li></ul><ul><li>  </li></ul>23/06/09
  9. 9. ULTRASTRUCTURE OF NEURON <ul><li>Cytoplasm : </li></ul><ul><li>A bundant of R.E.R </li></ul><ul><li>Polyribosomes </li></ul><ul><li>Basic dyes (a+b)  Nissl Bodies </li></ul><ul><li>lots of S.E.R. </li></ul><ul><li>Golgi bodies (perikaryon) </li></ul><ul><li>protein secreting cell </li></ul>23/06/09
  10. 10. ULTRASTRUCTURE OF NEURON <ul><li>Cytoplasm </li></ul><ul><li>M any mitochondria, most abundant in axon terminal </li></ul><ul><li>extensive cytoskeleton  axonal transport </li></ul><ul><li>One centriole  do not undergo cell divisions </li></ul>23/06/09
  11. 11. DENDRITE AND AXON <ul><li>AXON </li></ul><ul><ul><li>Single process u p to 100 cm </li></ul></ul><ul><ul><li>Originate from axon hillock </li></ul></ul><ul><ul><li>Devoid ribosome </li></ul></ul><ul><ul><li>Dilatation of distal portion  axon terminal  end bulbs  synapse </li></ul></ul><ul><ul><li>conducting impulse away from the soma </li></ul></ul><ul><ul><li>Axonal transport </li></ul></ul><ul><li>DENDRITES </li></ul><ul><ul><li>Multiple elongated processes </li></ul></ul><ul><ul><li>Cytoplasmic~perikaryon (devoid golgi complex) </li></ul></ul><ul><ul><li>Receiving stimuli </li></ul></ul>23/06/09
  12. 12. NEURONS CLASSIFICATION : <ul><li>According to the size and shape of the processes </li></ul>(Dorsal root & cranial nerve ganglia) (Pyramidal & purkinje) 23/06/09
  13. 13. NEURONS CLASSIFICATION : 23/06/09
  14. 14. NEURONS CLASSIFICATION : <ul><li>According to their function : </li></ul><ul><li>Sensory Neuron (afferent ) </li></ul><ul><ul><li>Receive sensory input  conduct impulses to CNS </li></ul></ul><ul><li>Motor Neuron (Efferent) </li></ul><ul><ul><li>CNS  conduct impulses to muscles, glands and other neurons </li></ul></ul><ul><li>Interneuron </li></ul><ul><ul><li>In the CNS as interconnectors, establish neuronal circuit between sensory and motor neuron </li></ul></ul>23/06/09
  15. 15. NEURON GROUPING <ul><li>CORTEX </li></ul><ul><ul><li>Neuron form six layers on the cerrebrum </li></ul></ul><ul><ul><li>Form three layers on the cerrebellum </li></ul></ul><ul><li>NUCLEI </li></ul><ul><ul><li>In subcortical region (thalamus, midbrain, brainstem and spinal cord) neuron form irregular cluster  nuclei </li></ul></ul><ul><li>GANGLION </li></ul><ul><ul><li>Cluster of neuron outside the CNS </li></ul></ul>23/06/09
  16. 16. FUNCTION OF NEURON <ul><li>R eceptive </li></ul><ul><ul><li>Receptor receive stimuli and tranduce into nerve impulse and transferro to other neuron </li></ul></ul><ul><li>I ntegrative </li></ul><ul><ul><li>Processing impulse on the higher center </li></ul></ul><ul><li>M otor </li></ul><ul><ul><li>Initiating motor respons and tranduse impulse to the effector </li></ul></ul>23/06/09
  17. 17. SYNAPS ES <ul><li>Sites of impulse transmission </li></ul><ul><li>Convert electrical signal into chemical signal </li></ul><ul><li>Permit neurons to communicate </li></ul><ul><li>Types of synapses : </li></ul><ul><ul><li>Axodentritic synapse </li></ul></ul><ul><ul><li>Axosomatic synapse </li></ul></ul><ul><ul><li>Axoaxonic synapse </li></ul></ul><ul><ul><li>Dendrodentritic synapse </li></ul></ul>23/06/09
  18. 18. SYNAPS 23/06/09
  19. 19. NEURO GLIAL CELLS <ul><li>Metabolic and mechanical support for neuron </li></ul><ul><li>10 times abundant than neurons </li></ul><ul><li>Neuroglial cells undergo mitosis </li></ul><ul><li>Classification : </li></ul><ul><ul><li>Oligodendrocytes </li></ul></ul><ul><ul><li>Astrocytes </li></ul></ul><ul><ul><li>Ependymal Cells </li></ul></ul><ul><ul><li>Microglia </li></ul></ul><ul><ul><li>Schwan cells  </li></ul></ul>CNS PNS 23/06/09
  20. 20. NEURO GLIAL CELLS <ul><li>Astrocytes </li></ul><ul><ul><li>Pedicles binds to capillaries and to the pia mater form glial limitans </li></ul></ul><ul><ul><li>Controlling the ionic & chemical env ironment of neurons </li></ul></ul><ul><ul><li>Energy metabolism </li></ul></ul><ul><ul><li>Form cellular scar tissue </li></ul></ul><ul><ul><li>Form the blood-brain barrier </li></ul></ul>23/06/09
  21. 21. NEURO GLIAL CELLS <ul><li>Oligodendrocytes </li></ul><ul><li>interfascicular </li></ul><ul><ul><li>Produce myelin sheath (electrical insulation) in CNS </li></ul></ul><ul><ul><li>A single cell wrap several axons (40 to 50) </li></ul></ul><ul><ul><li>Form nodes of Ranvier </li></ul></ul><ul><li>satellite </li></ul>23/06/09
  22. 22. NEURO GLIAL CELLS <ul><li>Schwann cells </li></ul><ul><ul><li>Analogue to Oligodendrocyte </li></ul></ul><ul><ul><li>Produce myelin sheath in the PN S </li></ul></ul>23/06/09
  23. 23. NEURO GLIAL CELLS <ul><li>Microglia </li></ul><ul><li>Scattered throughout the CNS </li></ul><ul><li>Clearing debris </li></ul><ul><li>Act as APC </li></ul><ul><li>Protect the CNS from viruses and microorganism </li></ul>23/06/09
  24. 24. NEURO GLIAL CELLS <ul><li>Ependymal Cells </li></ul><ul><ul><li>Low columnar ciliated epithelial cells  line the ventricles of the brain & central canal spinal cord </li></ul></ul><ul><ul><li>Formation of choroid flexus  produce CSF </li></ul></ul><ul><ul><li>Facilitates the movement of CSF </li></ul></ul>23/06/09
  25. 25. Anatomically divided in to : 06/23/09 NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM (CNS) PERIPHERAL NERVOUS SYSTEM (PNS)
  26. 26. THE CNS <ul><li>Consist of : </li></ul><ul><ul><li>Cerebrum </li></ul></ul><ul><ul><li>Cerebellum </li></ul></ul><ul><ul><li>Spinal cord </li></ul></ul><ul><li>No connective tissue  soft, gel like </li></ul><ul><li>When sectioned : </li></ul><ul><ul><li>White matter </li></ul></ul><ul><ul><li>Gray matter </li></ul></ul><ul><li>Covered by meninges </li></ul>06/23/09
  27. 27. CEREBRUM <ul><li>GRAY MATTER </li></ul><ul><ul><li>Contains neuronal cell bodies, dendrites and glial cells </li></ul></ul><ul><ul><li>Six layers composed of neuron </li></ul></ul><ul><ul><li>Neuron (pyramidal) : </li></ul></ul><ul><ul><ul><li>Afferent (sensory) </li></ul></ul></ul><ul><ul><ul><li>Efferent (motor) </li></ul></ul></ul><ul><li>WHITE MATTER </li></ul><ul><ul><li>Contains myelinated axons and myelin-producing oligodendrocytes </li></ul></ul>23/06/09
  28. 28. CEREBELLUM <ul><li>GRAY MATTER </li></ul><ul><ul><li>Three layers : </li></ul></ul><ul><ul><ul><li>Outer molecular layer </li></ul></ul></ul><ul><ul><ul><li>Central layer of large Purkinje cells </li></ul></ul></ul><ul><ul><ul><li>Inner granule layer </li></ul></ul></ul><ul><li>WHITE MATTER </li></ul><ul><ul><ul><li>The same as cerebrum </li></ul></ul></ul>23/06/09
  29. 29. SPINAL CORD <ul><li>GRAY MATTER (CENTRAL)  SHAPE OF “H” </li></ul><ul><ul><li>Central canal lined by Ependymal cells </li></ul></ul><ul><ul><li>Legs of the “H” form : </li></ul></ul><ul><ul><ul><li>Anterior horns </li></ul></ul></ul><ul><ul><ul><li>Posterior horns </li></ul></ul></ul><ul><ul><li>Neurons : large and multipolar </li></ul></ul><ul><li>WHITE MATTER (PERIPHERAL) </li></ul>23/06/09
  30. 30. PNS <ul><li>Bundles of nerve fibers (axons) outside the CNS & surrounded by connective tissue </li></ul><ul><li>Main component : </li></ul><ul><ul><li>Peripheral nerves </li></ul></ul><ul><ul><li>Ganglia </li></ul></ul><ul><ul><li>Nerve endings </li></ul></ul>06/23/09
  31. 31. NERVE FIBERS <ul><ul><li>Consist of axons enveloped by a special sheath </li></ul></ul><ul><ul><li>Group of fibers constitute the peripheral nerve </li></ul></ul><ul><ul><li>Two types : </li></ul></ul><ul><ul><ul><li>Myelinated fiber </li></ul></ul></ul><ul><ul><ul><li>Unmyelinated fiber </li></ul></ul></ul>23/06/09
  32. 32. NERVE FIBERS <ul><li>Myelinated fibers </li></ul><ul><ul><li>A single Schwann cell wraps around single axon  form myelin sheath  nodes of Ranvier </li></ul></ul><ul><li>Unmyelinated fibers </li></ul><ul><ul><li>A single Schwann cell envelopes several axon </li></ul></ul><ul><ul><li>Fibers enveloped within simple clefts of Schwann cells </li></ul></ul>23/06/09
  33. 33. MYELINATION PROCESS 23/06/09
  34. 34. CONDUCTION VELOCITY <ul><li>Depend on the extent of </li></ul><ul><li>Myelination : </li></ul><ul><li>Unmyelinated fibers </li></ul><ul><ul><li>No nodes of Ranvier  continuous conduction </li></ul></ul><ul><ul><li>Slower conduction </li></ul></ul><ul><li>Myelinated fibers </li></ul><ul><ul><li>Gap of myelin sheath ( nodes of Ranvier )  saltatory conduction </li></ul></ul><ul><ul><li>Faster conduction </li></ul></ul>23/06/09
  35. 35. CONNECTIVE TISSUE INVESTMENTS <ul><li>Epineureum </li></ul><ul><ul><li>Dense collagenous Con. Tissue with thick elastic fiber </li></ul></ul><ul><ul><li>Prevent damage by overstreching </li></ul></ul><ul><li>Perineureum </li></ul><ul><ul><li>Dense con. Tissue </li></ul></ul><ul><ul><li>Layers of epithelioids </li></ul></ul><ul><ul><li>Isolates neural environment (blood-nerve barrier) </li></ul></ul><ul><li>Endoneureum </li></ul><ul><ul><li>Loose con. Tissue </li></ul></ul><ul><ul><li>Regulation of microenvironment of nerve fiber </li></ul></ul>23/06/09
  36. 36. PERIPHERAL NERVE 06/23/09
  37. 37. PERIPHERAL NERVE 23/06/09
  38. 38. GANGLIA <ul><li>Ovoid structure containing neuronal cell bodies, glial cells supported by connective tissue </li></ul><ul><li>Function : Relay stations to transmit impulses </li></ul><ul><li>Types : </li></ul><ul><ul><li>Sensory ganglia </li></ul></ul><ul><ul><li>Autonomic ganglia </li></ul></ul>23/06/09
  39. 39. GANGLI A <ul><ul><li>Sensory Ganglia (cell bodies of sensory neuron) </li></ul></ul><ul><ul><ul><li>Unipolar cell bodies enveloped by cuboidal capsule cells </li></ul></ul></ul><ul><ul><ul><ul><li>Cranial ganglia : Associated with the cranial nerve </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Spinal ganglia : Associated with the spinal nerve </li></ul></ul></ul></ul><ul><ul><li>Autonomic Ganglia (cell bodies of postganglionic autonomic nerves) </li></ul></ul><ul><ul><ul><li>Multipolar neuron enveloped by satellite cells </li></ul></ul></ul><ul><ul><ul><li>Some are located within certain organ (intramural) </li></ul></ul></ul>23/06/09
  40. 40. DORSAL ROOT GANGLIA 06/23/09
  41. 41. FUNCTIONAL CLASSIFICATION OF NERVES <ul><li>Sensory nerve fibers </li></ul><ul><ul><li>Carry sensory input from the cutaneus/ viscera area  to CNS </li></ul></ul><ul><li>Motor nerve fibers </li></ul><ul><ul><li>Originate in the CNS  carry motor impulses to the effector organs </li></ul></ul>06/23/09
  42. 42. FUNCTIONAL CLASSIFICATION OF MOTOR COMPONENT <ul><li>Somatic nervous system </li></ul><ul><li>Provide motor impulses to skeletal muscles </li></ul><ul><li>Cells bodies (multipolar) originate in the motor nuclei of the brain or ventral horn of spinal cord </li></ul><ul><li>The axon travel to the skeletal muscle via cranial or spinal nerve </li></ul><ul><li>Autonomic nervous system </li></ul><ul><li>Provide motor impulses to the smooth muscle of viscera, cardiac muscle, secretory cells </li></ul><ul><li>HOMEOSTASIS </li></ul>06/23/09
  43. 43. AUTONOMIC NERVOUS SYSTEM <ul><li>ANS = two-neuron network </li></ul><ul><li>First Neuron </li></ul><ul><ul><li>Neuron in CNS </li></ul></ul><ul><ul><li>Axon (preganglionic fibers) form a synapse with second multipolar neuron in ganglion </li></ul></ul><ul><li>Second Neuron </li></ul><ul><ul><li>Neuron in the Ganglion </li></ul></ul><ul><ul><li>Axon to the effectors (postganglionic fibers) </li></ul></ul>23/06/09
  44. 44. AUTONOMIC NERVOUS SYSTEM <ul><li>SYMPHATETIC SYSTEM </li></ul><ul><li>The nuclei located in the thoracic and lumbar segment of spinal cord </li></ul><ul><li>Preganglionic fibers leave the CNS by way of ventral roots </li></ul><ul><li>The chemical mediator postganglionic fibers is norepinephrine </li></ul><ul><li>PARASYMPHATETIC SYSTEM </li></ul><ul><li>The nuclei located in the medulla and midbrain and in the sacral portion of spinal cord </li></ul><ul><li>Pre ganglionic fibers leave the CNS trough cranial nerve III, VII, IX and X and also trough II, III, IV sacral nerve </li></ul><ul><li>The ganglion located near the effector organs </li></ul><ul><li>The chemical mediator pre and postganglionic fibers is acethilcholine </li></ul>06/23/09
  45. 45. MENINGES <ul><li>The dura mater </li></ul><ul><ul><li>dense, collagenous connective tissue </li></ul></ul><ul><li>The arachnoid layer : </li></ul><ul><ul><li>fibroblasts, collagen & elastic fibers </li></ul></ul><ul><ul><li>Layer in contact with dura mater & a system of trabeculae </li></ul></ul><ul><ul><li>Form arachnoid villi </li></ul></ul><ul><li>The pia mater </li></ul><ul><ul><li>Loose con. Tissue with blood vessel </li></ul></ul><ul><ul><li>There is a physical barrier between pia mater & neuron </li></ul></ul>06/23/09
  46. 46. BLOOB-BRAIN BARRIER <ul><li>Prevents the passage of </li></ul><ul><li>substances (bacterial, toxic, </li></ul><ul><li>Chemical…) from blood to </li></ul><ul><li>nerve tissue </li></ul><ul><li>Endothelial of capillary </li></ul><ul><ul><li>Occluding junction </li></ul></ul><ul><ul><li>No fenestration </li></ul></ul><ul><li>Expansions of Astrocytes cell processes that envelope the capillary </li></ul>↓ permeability 23/06/09
  47. 47. CHOROID FLEXUS <ul><li>Choroid flexus co nsist of loose conn . tissue of the pia matter, covered by a simple/ low columnar epith .  ion transporting cells </li></ul><ul><li>Elaborate CSF  fill the ventricles  subarachnoid space (arachnoid villi)  venous </li></ul><ul><li>CSF function  metabolism and protective of CNS </li></ul>23/06/09
  48. 48. CEREBROSPINAL FLUID <ul><li>Composition </li></ul><ul><ul><li>clear, </li></ul></ul><ul><ul><li>low density & protein content </li></ul></ul><ul><ul><li>High Na, K, Cl </li></ul></ul><ul><li>Function </li></ul><ul><ul><li>Metabolic </li></ul></ul><ul><ul><li>Liquid cushion </li></ul></ul><ul><li>Blood-CSF barrier </li></ul><ul><ul><li>Zonulae occludents </li></ul></ul>23/06/09
  49. 49. NERVE REGENERATION <ul><li>Diseases affecting Schwann cells  loss of myelin (segmental demylination) </li></ul><ul><li>Nerve injury  induced axonal degeneration (wallerian degeneration)  followed by regeneration </li></ul><ul><li>Axon reaction : </li></ul><ul><ul><li>Local changes </li></ul></ul><ul><ul><li>Anterograte changes </li></ul></ul><ul><ul><li>Retrograte changes </li></ul></ul>06/23/09
  50. 50. Axon reaction <ul><li>Local reaction </li></ul><ul><ul><li>Severe ends of axon retract & cuts membrane fuses </li></ul></ul><ul><ul><li>Macrophage & fibroblasts infiltration </li></ul></ul><ul><li>Anterograde reaction </li></ul><ul><ul><li>Axon terminal degeneration </li></ul></ul><ul><ul><li>Schwann cells proliferation form a column of Schwann (endoneureum is essential for proliferation of Schwann cells) </li></ul></ul><ul><li>Retrograde reaction </li></ul><ul><ul><li>Chromatolysis in perikaryon </li></ul></ul><ul><ul><li>Several sprouts of axons emerge from proximal stump </li></ul></ul><ul><ul><li>Axon sprouts enter the schwan tubes and guided to reach the target organ </li></ul></ul>22/04/2009
  51. 51. Axon reaction 06/23/09
  52. 52. REGENERATION OF CNS ?? <ul><li>Regeneration nerve fibers in CNS is not possible, because : </li></ul><ul><ul><li>An endoneureum is not present </li></ul></ul><ul><ul><li>Oligodendrocytes do not proliferate </li></ul></ul><ul><ul><li>Astrocytes deposit scar tissue (plaque) </li></ul></ul>23/06/09
  53. 53. THANK YOU 06/23/09

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