1. PRESENTED BY- DR.A.RAMYA (First year pg)- CHAIRPERSON - DR.M.RAMANI (Prof)MODERATORS - DR.DEVENDER REDDY (Assoc.Prof) DR.NEELIMA (Asst.Prof)

2. INTRODUCTION The central nervous system consists of the brain andspinal cord, which are composed of neurons, thesupporting glial cells and blood vessels. Basic structure of a neuron consists of -cell body -dendrites -axon 3. Structure of Neuron 4. Basic neuron types-Based on the arrangement of the axon and dendrites, with respect to cell body. 5. ULTRASTRUCTURE OF NEURON. 6. CEREBRAL CORTEX The cerebral hemispheres consists of a convoluted cortex of grey matter overlying central medullary mass of white matter. The grey matter consists of neuron cell bodies and their dendritic interconnections & glial cells. The white matter conveys fibers between different parts of the cortex and from other parts of CNS. 7. Contd.. The cortex is a thin layer of neurons and their interconnections, measuring few mm and contains 3obillion neurons. The evolved cortex in mammals called neocortexconsists of 6 layers of neurons. 8. HISTOLOGY OF GREY MATTER. 9. TYPES OF CORTEX Neocortex >90 % of our total cortical area. -6 layered structure. -Refered to as homogenic cortex. Paleocortex Covers some parts of the base of thetelencephalon.(olfactory area) -Forms heterogenic cortex. archicortex The hippocampal formation. 10. Neuron Cell types Two principal cell types are present in neo cortex. 1.The pyramidal cell 2.The Stellate cell Other cells are 3. The cells of Martinotti 4.Fusiform cells 5.Horizontal cells of cajal 11. .. 12. 1. Pyramidal Cell2. Fusiform Cell3. Granular (Stellate) Cell4. Horizontal Cell of Cajal5. Cells of Martinottia: axon 13. PYRAMIDAL CELLS Pyramid shaped cellbodies. About 10 microns to 70microns in diameter. Axon arises from thebase and the dendritefrom the apex. The largest of thepyramidal cells are calledthe BETZ cells. 14. Functions of pyramidal cels The apical dendrites of pyramidal cells are studdedwith dendritic spines. These are numerous small projections that arethe preferential site of synaptic contact. It has been suggested that dendritic spines may be the sitesof synapses that are selectively modified as a result oflearning. Most or all pyramidal cells have long axons that leave thecortex to reach either other cortical areas or tovarious subcortical sites. Therefore, pyramidal cells are the principal outputneurons. 15. STELLATE CELLS-Also known as granular cells.-They are the principal interneurons of cortex .-These come in a wideassortment of shapes.-They are typically small (< 10micrometres) multipolar neurons. 16. FUNCTIONS OF STELLATE CELLS The short axons of stellate cells do not leave thecortex. Stellate cells are the principal interneurons of theneocortex. 17. CELLS OF MARTINOTTI Small polygonal cells. Have very few short dendrites. The axon extends towards the surface and bifurcate torun horizontally in most superficial layers. Forms synapses with the pyramidal cells. 18. FUSIFORM CELLS Spindle shaped cells. They are oriented at right angles to the cortex. Axon arises from the side of the cell body and passessuperficially. Dendrites extend from each end of the cell bodybranching into deeper and more superficial layers. Functions are similar to that of pyramidal cells. 19. HORIZONTAL CELLS OF CAJAL (OR)RETZIUS CAJAL CELLS Small ,spindle shaped. Oriented parallel to the surface. Least common cell type. Found only in most superficial layer. Axons pass laterally to synapse with dendrites ofpyramidal cells. They are prominent during development, butdisappear after birth. 20. LAYERS OF NEOCORTEXDiffering in neuron morphology, size and population density, thereare 6 layers in the neocortex. 1.plexiform or molecular layer2.outer granular layer3.outer pyramidal cell layer4.inner granular layer5.inner pyramidal cell layer/ganglion cell layer6.multiform cell layer -The six neocortical layers are not equally prominenteverywhere. They form granular & agranular layers. 21. 1.PLEXIFORM LAYER Most superficial layer. Contains many dendriticand axonal synapses withone another. Sparse nuclei are seenthat belongs toneuroglia. Occasional horizontalcells of cajal are seen. 22. 2.OUTER GRANULAR LAYER Dense population ofsmall pyramidal cellsand stellate cells. Also contains variousaxons and dendriticconnections. 23. 3.PYRAMIDAL CELL LAYER Moderate sized pyramidalcells predominate. Large pyramidal cells arepresent in further deeperlayers. Martinotti cells are alsopresent. 24. 4.INNER GRANULAR LAYER Consists of densely packed stellate cells. 25. 5.GANGLIONIC LAYER Large pyramidal cells Stellate cells (few) Cells of martinotti Huge pyramidal Betzcells of motor cortex arepresent. Hence the nameganglion cell layer. 26. 6.MULTIFORM CELL LAYER All morphological forms are found in this layer. Fusiform cells in deeper and other cells are present superficially in this layer. 27. Layer 4&5. 28. INTERCONNECTIONS OF CORTEX Afferent fibers synapse high(superficially) in thecortex with dendrites of efferent neuron. Efferent fibers, typically the axons of pyramidal cellstend to give off branches. These branches pass back into the superficial layersto communicate with their own dendrites. This can be via interneuronal connectins or involvingother cortical cell types. 29. .. 30. ContdAfferent Input Efferent OutputAssociation nuclei(Thalamus)- corticothalamic fibersOther cortical areas- corticocortical fibersIntralaminar nuclei(Thalamus)- corticostriate fibers to brainstem & spinal cord 31. NEUROGLIAL CELLS In addition to neurons, the cortex contains supportingneuroglial cells. They are- 1. Astrocytes 2. Oligodendroglial cells 3. Microglial cells 4. Ependymal cells 32. ASTROCYTES Function(s):. Most numerous glial cells in..Supply of nutrients tothe grey matter.neurons. The nucleus is round to oval..Removes excesswith open chromatin and neurotransmitters..Maintains appropriate balanceperipheral nucleoli.of Ca2+ and K+ The cytoplasm is highly ions (which are important inpassing nervebranched that occupy most impulses at synapses).of the neuropil - ..Helps migration of neuronsduring braindevelopment.protoplasmic astrocytes..Aids formation of the The foot process act as BBB blood-brain barrier.called glia limitans. 33. OLIGODENDROCYTES -Found mainly adjacent toneurons/axon.-FUNCTION- myelination ofneurons.-They develop an artifacturalvacuolisation around nuclei thusa halo appears around thenucleus.-They are relatively large cellswith dispersed nuclear chromatinand perinuclear halo.-They also aggregate around nervecell bodies in grey matter andfunction as supporting cells. 34. MICROGLIAL CELLS Small cells of mesenchymalorigin.- Have elongated nuclei andrelatively little cytoplasm.- The cytoplasm forms fine,highly branched processes.- In response to tissue damage,they transform into largeamoeboid phagocytic cells.Protects neurons fromdisease process.- They function as scavengersof nervous system.- CNS representatives ofmacrophage monocytedefence system. 35. EPENDYMAL CELLSFUNCTIONS-Protection: Forms lining of theventricles of the brain and-Forms the epithelial lining of central canal of the spinal cord.ventricles and spinal cord. Forms cerebrospinal fluid (CSF).-Aids circulation of cerebrospinal -Cuboidal or low columnar in fluid (CSF).shape.-cells are bound at the luminalsurface by epithelialjunctional complexes.The bases of cells taper andbreak into fine branches whichramify into underlying layer ofastrocytic processes. 36. Staining of components of nervoussystem NEURON: General architecture -routine H&E stain. Hematoxylin & von Giesan stain- highlights vascular changes.- emphasises myelin staining.- provides cellular cytology. Nissls substance-basic dyes-methylene blue,toluedene blue,neurtal red,cresyl violet 37. CRESYL VIOLET, TOLUEDENE BLUE AND HEAVY METAL IMPREGNATION METHOD 38. HEAVY METAL IMPREGNATION TECHNIQUE WITH GOLD HMI techniques with gold and silver are valuable in the study of neuronal morphology. Cajal and Golgi are the pioneers of neuroanatomy who employed these techniques. 39. Contd.. IHC OF NEURONS Anti-neurofilament antibody staining- Nf 70, Nf 150,Nf 200(cytoskeletal protiens) Ab to neuron specific enolase(cytoplasmic protiens) Protiens associated with neurosecretory granules Chromogranin A Synaptophysin 40. IHC- ANTIBODY TO NEUROFILAMENT PROTEIN Nf-70 41. Contd.. For staining axons and neuronal processes blockimpregnation methodammonical silver soln. Biclschowskys silver stain(silver nitrate soln) neurofibrils, dendrites & axons in parrafin &frozen sections.(Stains black) Eriksons staining for axons(ammonical silver soln) Earers method for staining degenerated nerve fibers-stains brown to black(N-pale yellow) Myelin-solochrome cyanin+ aq. Iron alumstainsmyelin sheaths blue. 42. SILVER STAINED SECTION OF CEREBRALCORTEX 43. SPECIAL STAINS FOR NEUROGLIAL TISSUE ASTROCYTES- Normal- Cajals gold sublimate.reactive/gliosis- lithium carbonate technique, silverstaining, PTAH(phospho tungstic acid hematoxylin) Astroglial neoplasms-GFAP immunoperoxidase. PTAH-stains astrocyte fibrils, nuclei,myelin- blue &neurons- pink Cajals stain fibrous & protoplasmic astrocytes darkpurple to black( background- light purple) 44. ASTROCYTES-IHC Staining for GFAP 45. Contd.. EPENDYMAL CELLS-iron hematoxylin/PTAH/GFAP immunoperoxidase. OLIGODENDROCYTES- H&E, toluedene blue. MICROGLIA-silver techniques, macrophage marker CD68. 46. DISEASES OF CEREBRAL CORTEX Alzheimerss disease- senile plaques,neurofibrillarytangles. Lewy body dementia-Neuronal inclusions in cerebralcortex. Huntingtons disease- polyglutamin containinginclusions. Vascular dementia- multiple cerebral infarcts. NEOPLASMS- astrocytoma, oligodendrocytoma. Picks disease, tau-pathies, prion disease. 47. CEREBRAL INFARCT 48. Silver stain Alzheimers disease 49. - Amyloid deposition in corticalarteriole in CEREBRALAMYLOID ANGIOPATHY IHC Stain for A-beta deposits 50. OLIGODENRROGLIOMA 51. Astrocytoma 52. Silver stain-PICKDISEASE showing Pickbodies(inclusions) 53. PRION DISEASE- Corticalplaques surrounded byspongiform change in vCJD. 54. REFERENCE WHEATERS functional histology Page399,123-127 5thedition. Text book of histology- I.B.SINGH JOHN D.BANCROFT- theory and practice of histologicaltechniques-5th edition. ROBBINS & COTRAN-8th edition INTERNET 55. --THANK YOU