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Midterm

BIOL_273_Midterm_1_Notes.doc

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Department
Biology
Course
BIOL 273
Professor
Vivian Dayeh
Semester
Winter

Description
BIOL273Midterm1NotesNeurophysiologyIntroductionThenervoussystemisanetworkofnervecellslinkedtogethertoformtherapidcontrolsystemofthebodyNervecellsalsocalledneuronsaredesignedtocarryelectricalsignalsrapidlyoverlongdistancesoTheylinktogethertotransferasignalbypassingchemicalsignalscalledneurotransmittersacrossthesmallgapbetweeneachneuroncalledasynapseoSometimesmorerarelytheyareinsteadlinkedbygapjunctionsPathwayspathsalongwhichthesesignalstravelarenotnecessarilylinearsometimesasignalinfluencesmultipleneuronsormanyneuronsaffectonesingleneuronOrganizationoftheNervousSystemSensoryreceptorsmonitorconditionsintheinternalandexternalenvironmentsofthebodyandsendthisinformationthroughafferentorsensoryneuronstothecentralnervoussystemThecentralnervoussystemorCNSistheintegratingcenterforneuralreflexesitreceivestheseafferentsignalsandthendecideswhattodowithitThenifanactionisneededthesignalforthisissentoutthroughefferentneuronsoEfferentneuronsaredividedintothesomaticmotordivisionwhichcontrolsskeletalmusclesandtheautonomicdivisionwhichcontrolssmoothandcardiacmusclesexocrineandsomeendocrineglandsandsometypesofadiposetissueAutonomicneuronsarefurtherdividedintosympatheticandparasympatheticbranchesoTheafferentandefferentneuronsformtheperipheralnervoussystemCellsoftheNervousSystemThenervoussystemiscomposedprimarilyoftwocelltypesglialcellssupportcellsandnervecellsneuronsthebasicsignalingunitsofthenervoussystemNeuronsareExcitableCellsthatGenerateandCarryElectricalSignalsTheneuronisthefunctionalunitofthenervoussystemthesmalleststructurethatcancarryoutthefunctionsofasystemoSEEFIGURE82PAGE242NeuronshavelongthingscalledappendagesorprocessesstickingoutfromtheircellbodyeitherdendriteswhichreceiveincomingsignalsoraxonswhichcarryoutgoinginformationoTheshapenumberandlengthofthesethingsvaryfromneurontoneuronTheCellBodyistheControlCenteroftheNeuronThecellbodyofthenerveisjustlikeatypicalcellbodyAcytoskeletonextendsintotheaxonanddendritesThepositionofthecellbodyinrelationtothedendritesetcvarieswithdifferentkindsofneuronsbutalmostalwaysitissmalllessthan110oftotalneuronvolumeDendritesReceivingIncomingSignalsDendritesarethinbranchedprocessesthatreceiveincominginformationfromneighboringcellsTheyincreaseacellssurfaceareaBasicallytheirjobistoreceiveincominginformationandsendittoanintegratingregionwithintheneuronegthenucleusofthecellAxonsCarryOutgoingSignalstotheTargetMostneuronsonlyhaveoneoftheseItcomesoutofapartofthecellcalledtheaxonhillockTheycanbeaslongasameterlongorjustafewmicrometerslongButalongtheaxontheybranchandformcollateralsoEachcollateralendsinanaxonterminalThefunctionalityofanaxonistotransmitoutgoingelectricalsignalsfromtheintegratingcenterienucleusoftheneurontotheendoftheaxonTheregionwhereanaxonterminalmeetsitstargetcelliscalledasynapseoTheneuronwhichdeliversthesignaltothesynapseiscalledthepresynapticcelloThecellthatreceivesthesignalisthepostsynapticcelloThenarrowspacebetweenthetwocellsisthesynapticcleftGlialCellsaretheSupportCellsoftheNervousSystemGlialcellsprovideimportantphysicalandbiochemicalsupporttoneuronsTheyoutnumberneuronsinthenervoussystemby10501NeuronsdonothavemuchoutwardsupportsoglialcellsprovidestructuralstabilitytoneuronsbywrappingaroundthemoTheyalsoprovidemetabolicsupporttoneuronsoAndhelpmaintainhomeostasisofthebrainsextracellularfluidbytakingupexcessmetabolitesandKTheperipheralnervoussystemhastwotypesofglialcellsSchwanncellsandsatellitecellsThecentralnervoussystemhasfourtypesofglialsupportcellsoligodendrocytesastrocytesmicrogliaandependymalcellsoAstrocytesarehighlybranchedcellswhichtransfernutrientsbetweenneuronsandbloodvesselsoMicrogliaarespecializedimmunecellswhichresidepermanentlywithintheCNSandremovedamagedcellsandforeigninvadersoEpendymalcellsareepithelialcellsthatcreateaselectivelypermeablebarrierbetweencompartmentsinthebrainoSchwannoligodendrocytesintheCNSsupportandcellsintheperipheralnervoussystemandinsulateaxonsbycreatingmyelinmultipleconcentriclayersofphospholipidsmembraneMyelinformswhentheseglialcellswraparoundanaxonandtheysqueezeouttheglialcytoplasmtoformmembranelayersSEEFIGURE86PAGE247Soasingleaxoncanhaveupto500SchwanncellswrappedarounditmakingthemyelinsheathBetweenthesecellsthereisaverysmallparttheaxonmembranestillincontactwiththeextracellularfluidcalledanodeofRanvieroSatellitecellsformsupportivecapsulesaroundnervecellbodieslocatedingangliaElectricalSignalsinNeuronsNerveandmusclecellsarecalledexcitabletissuesbecausetheycanpropagateelectricalcellswhenionsmoveacrossthecellmembraneTheNernstEquationPredictsMembranePotentialforaSingleIonMembranepotentialistheelectricaldisequilibriumwhichresultsfromtheunevendistributionofionsacrossthecellmembraneoItisaffectedbytwofactorsConcentrationgradientsofionsacrossthemembraneNormallysodiumchlorideandcalciumaremoreconcentratedintheextracellularfluidthaninthecytosolinsidewhilepotassiumismoreconcentratedinthecellthaninextracellularfluid
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