Cells of the CNS 4p.pdf - 11/2/2012 Read through this...

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11/2/20121Read through this Powerpoint presentation,keeping in mind the objectives of this directedstudy.Some of this material is review, but you will beresponsible for the material presented.However, you will not be required to identifystructures from diagrams or micrographs.One question from this material will be on thequiz on November 7th.Two questions will beon the final exam.ObjectivesAt the end of this directed study you should beable to:Discuss the following different cellular components ofthe central nervous system in terms of their functionand location:NeuronsGliaAtrocytesMicrogliaOligodendrocytesEpendymaDiscuss the components of the blood-brain barrierand how this barrier restricts entry of both harmfulsubstances and microorganisms as well as therapeuticagents.The main cellular components of the CNS include:NeuronsThere are about 1 billion neurons in the CNSmaking up 10% of total cell numbersGliaThere are about 10 billion glia cells in the CNSmaking up 90% of total cell numbers
11/2/20122Table 1-3. Cell Types in the Central Nervous SystemCell or Cell PartPrincipal LocationPrincipal FunctionNeurons, dendrites, synapsesGray matterCollect, integrate, transmitinformation; synthesizemacromoleculesAxonsWhite matterConduct informationOligodendrocytesWhite (and gray) matterForm myelin sheathsProtoplasmic astrocytesGray matterProvide mechanical and metabolicsupport, response to injuryFibrous astrocytesWhite matterProvide mechanical and metabolicsupport, response to injuryMicrogliaGray (and white) matterPhagocytosis, response to injuryEpendymal cellsWalls of ventriclesLine ventricles and choroid plexus,secrete cerebrospinal fluidIn Blumenfeld, the cellular components of the CNS are classified as follows:We will consider each cell type separately in this presentationNEURONSNEURONSA number of conventions have evolved to classify and name neurons. Oneof the oldest, devised by Golgi in the late 1800’s, is based on thecomplexity of the dendritictree of the neuron. Through this approachcells are classified as unipolar, bipolar and multipolar neuronsUnipolar cellshave only one cell process, and are primarily found ininvertebrates. However, vertebrate sensory neurons are another form ofthis type of cell. Because these cells start out developmentally as bipolarneurons and then become unipolar as they mature, they are calledpseudo-unipolar cells.Bipolar cellsare present in theretinaand theolfactory bulb.Multipolar cellsmake up the remainder of neuronal types and are,consequently, the most numerous type. These have been further sub-categorized intoGolgi type IIcells that are small neurons, usuallyinterneurons, andGolgi type Icells that are large multipolar neurons.

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