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Neuroanatomy - The structure and Functional localization of the Cerebral Cortex_e0b3b0ce2d4520c315e6

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NeuroanatomyThe Structure & FunctionalLocalization Of The Cerebral Cortexنيملاعلا بر هلل دمح
Structure of the CerebralCortexIt is the outer layer of gray matercovering the cerebrumItis 1.5 to 4.5 mm thick(thickest in thecrest of gyri and thinnest in the sulci)Contains around10 billion neuronsIt contains nerve cells, neuroglia &nerve cellsThere are thefollowing types of nervecells:1.Pyramidal2.Stellate3.Fusiform4.Horizontal cells of Cajal5.Cells of Martinotنيملاعلا بر هلل دمح
Nerve Cells of the CerebralCortex1.Pyramidal cells: 10-50 um . Betz cells are120 um . These are multipolar nerve cellswith dendritic spines2.Stellate cells:(granule cells) polygonal 8um in diameter. They have short axonswhich ends on neighboring neurons. Theymay bespiny (excitatory) or aspiny(inhibitory) neurons.3.Fusiform cells:Their axis is vertical to thesurface.They are situated deep in thecortex. Their axons mainly project to thethalamus4.Horizontal cells of Cajal:Their long axis isparallel to the surface and are present inthe superficial parts of the cortex. Connectfar areas of the cortex. They are especiallyessential for brain development.5.Cells of Martinot:These are smallmultipolar cells present in all parts of thecortex with their axons perpendicular tothe surface. They are active in dampeningof overactive neuronsنيملاعلا بر هلل دمح
Nerve Fibers of theCerebral Cortex1.Radial fibers:run at right anglesto the cerebral surface. They areformed by afferent fibers andefferent projection, association,and commissural fibers especiallypyramidal, stellate and fusiformcells.2.Tangenital fibers: Run parallel tothe surface. They are composedof mainly afferentfibers andcollaterals of cortical cells. Theyform the outer and innerbands ofBaillarger.These bands aremarked in the sensory regionsespecially in the visual cortexwhere they formStria of Gennarihence the namestriate cortexنيملاعلا بر هلل دمح
Layers of the CerebralCortexAccording to type, density andarrangement of cells, there are sixlayers of the cerebral cortex (fromsuperficial to deep):1.Molecular (plexiform) Layer2.External Granular(plexiform)Layer3.External Pyramidal Layer4.Internal Granular (plexiform)Layer5.Internal Pyramidal (ganglionic)Layer6.Multiform layer (layer ofpolymorphic cells)نيملاعلا بر هلل دمح
Variations of CorticalStructureTwo types of cortical structure:1.Homotypical structure (six layers)2.Heterotypical (not six layers):Granular(stellate cells)layers 2 and 4are welldeveloped while 3 & 5 arepoorly developed. Layers 2-5 are merged together. Thisis the case inpostcentralgyrus, sup. Temp. gyrus &hippocampal formationAgranular: layers 3 & 5arewell developed inprecentralgyrus and otherfrontal lobe areasنيملاعلا بر هلل دمح

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