NERVOUS SYSTEM(神经组织) PPT完整版

NERVOUSSYSTEMFUNCTIONSOFTHENERVOUSSYSTEM1.SensoryInput–Sensoryreceptorsmonitornumerousexternaladinternalstimulithatmaybeinterpretedastouch,temperature,taste,smell,sound,bloodpressure,andbodyposition.Actionpotentialtravelsfromthesensoryreceptorstospinalcordandbrainwheretheyareinterpreted.2.Integration–Thebrainandspinalcordarethemajororgansforprocessingsensoryinputandinitiatingresponses.3.Homeostasis–Thisfunctiondependsontheabilityofthenervoussystemtodetect,interpretandrespondtochangesininternalandexternalcondition.4.MentalActivity–Thebrainisthecenterofmentalactivitysuchasconsciousness,memory,andthinking.5.ControlofMusclesandGlands–Skeletalmusclescontractonlywhenstimulatedbythenervoussystem.Thenervoussystemalsoparticipateincontrollingcardiacmuscle,smoothmuscleandmanyglands.DIVISIONSOFTHENERVOUSSYSTEM1.Thecentralnervoussystem(CNS)consistsofthebrainandspinalcord,whereastheperipheralnervoussystem(PNS)consistsofnervesandganglia.2.ThesensorydivisionofthePNStransmitsactionpotentialstotheCNS;themotordivisioncarriesactionpotentialsawayfromtheCNS.3.Thesomaticmotornervoussysteminnervatesskeletalmuscleandismostlyundervoluntarycontrol.Theautonomicnervoussysteminnervatescardiacmuscle,smoothmuscle,andglandsanditismostlyunderinvoluntarycontrol.4.Theautonomicnervoussystemisdividedintosympathetic,parasympatheticandentericportions.

CELLSOFTHENERVOUSSYSTEMNeuronorNerveCell

Receivestimuliandtransmitactionpotentialstootherneuronsoreffectororgans.Partsinclude;

1.Cellbody–consistsofasinglenucleus,roughER,golgiapparatusandmitochondriaandstructuresofthecell.

2.Dendrites–arethecytoplasmicextensionsoftheneuron’scellbody.Itfunctiontoreceiveinformationfromanotherneuron.

3.Axon–alongcellprocessoftheneuron.ItconductsactionpotentialsawayortowardstheCNS.CELLSOFTHENERVOUSSYSTEMTypesofneurons:

1.Multipolar–severaldendritesandoneaxon.LocationismotorandCNSneuron.

2.Bipolar–onedendriteandanaxon.Foundintheeyeandnose.

3.Unipolar–withsingleaxononly.Locatedmostlyonsensoryneurons.CELLSOFTHENERVOUSSYSTEMNeuroglia:

1.Astrocytes–star-shape,providestructuralsupportofbloodvesselsandserveasblood-brainbarrier.

2.EpendymalCells–squamousepithelial-likethatlinestheventricleofthebrain,circulateCSF.

3.Microglia–smallmobilecellsthatprotectsCNSfrominfection.Becomephagocyticinresponsetoinflammation.

4.Oligodendrocytes–surroundseveralaxonsthatformmyelinsheathsandenclosedunmyelinatedaxonsintheCNS.

5.SchwannCells–singlecellsurroundingaxonsthatformmyelinsheathsandenclosedunmyelinatedaxonsinthePNS.OrganizationoftheNervousTissue Nervoustissueconsistsofwhitematterandgraymatter.GraymatterformsthecortexandnucleiinthebrainandgangliainthePNS.WhitematterformsnervetractsintheCNSandnervesinthePNS.ELECTRICALSIGNALSANDNEURALPATHWAYSTheRestingMembranePotential:Isthechargedifferenceacrossthemembraneofunstimulatedcell(polarizedcell).Na⁺channels,andsomebutnotallK⁺channelsareclosed.FewK⁺diffusedowntheirconcentrationgradientthroughtheopenK⁺channelsmakingtheoutsideofthecellpositivelycharged.Depolarization:Na⁺channelsareopen.FewNa⁺diffusedowntheirconcentrationgradientthroughtheopenchannelsmakingtheinsideofthecellpositivelycharged.Repolarization:

Na⁺channelsareclosedandNa⁺movementintothecellsstops.MoreK⁺channelsopen,K⁺movementoutofthecellincreases,makingtheoutsideofthecellpositivelycharged.ActionPotentials:

Anactionpotentialoccurswhenthechargeacrossthecellmembraneisbrieflyreversed.ELECTRICALSIGNALSANDNEURALPATHWAYSELECTRICALSIGNALSANDNEURALPATHWAYSTheSynapse:1.

Thesynapseisthepointofcontactbetweentwoneuronsorbetweenaneuronandsomeothercell(muscleorgland).

2.Anactionpotentialarrivingatthesynapsecausesthereleaseofaneurotransmitter(Ach)fromthefreesynapticterminal,whichdiffusesacrossthesynapticcleftandbindstothereceptorsofthepostsynapticmembrane.ELECTRICALSIGNALSANDNEURALPATHWAYSSomeoftheimportantNeurotransmittersofthenervoussystem:1.Acetylcholine

(Ach)–excitatoryandinhibitory,locatedinthebrainandspinalcord,nervetracts,skeletalmusclejunction(NMJ)andANS.2.Norepinephrine–excitatoryandinhibitory,locatedinthebrainstem,nervetracts,brainandspinalcord.3.Serotonin–generallyinhibitoryandlocatedinthebrainstem,nervetracts,brainandspinalcord.4.Dopamine–generallyexcitatory,locatedinbrainstem,nervetracts,andANS.

ELECTRICALSIGNALSANDNEURALPATHWAYSReflexes:

ItisaninvoluntaryreactioninresponsetoastimulusappliedtotheperipheryandtransmittedtotheCNS.Reflexarcistheneuronalpathwaybywhichareflexoccur.Thereflexarcisthebasicfunctionalunitofthenervoussystembecauseitisthesmallest,simplestpathwaycapableofreceivingastimulusandyieldingaresponse.Componentsofreflexarc:(1)Sensoryreceptor,(2)Sensoryneuron,(3)Interneurons,(4)Motorneuronand(5)Effectororgan.ELECTRICALSIGNALSANDNEURALPATHWAYSNeuronalPathways:

ConvergingPathways-havetwoormoreneuronsthatsynapsewiththesameneuron.Thisallowsinformationtransmittedinmorethanoneneuronalpathwaytoconvergeintoasinglepathway.

DivergingPathways–asingleaxondivides(diverge)intotwoandsynapsewithmorethanoneotherneuron.Thisallowinformationtransmittedinoneneuronalpathwaytodivergeintotwoormorepathways.THESPINALCORD1.Spinalcordextendsfromtheforamenmagnumtothelevelofsecondlumbarvertebra.2.Thespinalcordhasacentralgray

partorganizedintohornsandaperipheralwhitepartformingnervetracts.3.Rootsofspinalnervesextendoutofthecord.THESPINALCORDSPINALCORDREFLEXES1.Theknee-jerkreflexoccurswhenthequadricepsfemorismuscleisstretched.2.Thewithdrawalreflexremovesabodypartfromapainfulstimulus.SPINALNERVES1.Thespinalnervesexitfromthecervical,thoracic,lumbar,andsacralregions.2.Thenervesaregroupedintoplexuses.Types:

1.cervicalplexus–suppliesnervestotheneckandheadanddiaphragm.2.Brachialplexus–suppliesnervetoupperlimbs.3.Lumbosacralplexus–suppliesnervestolowerlimbs.BRAINBRAIN:BrainstemandCerebellumBrainstemconnectsthespinaltothebrain.Itconsistsofthefollowing:

1.Medullaoblongata–whichcontrolstheheartrate,breathing,swallowingandbalance.

2.Pons–containsrelaynucleibetweenthecerebrumandcerebellum.

3.Midbrain–isinvolvedinhearingandvisualreflexes.

Reticularformationarenucleiscatteredthroughoutthebrainstemwhichisimportantinregulatingcyclicalmotorfunctionsandinvolvedinmaintainingconsciousnessandinsleep-wakecycle.Cerebellum

isattachedtothebrainstem.Itisinvolvedinbalance,maintenanceofmuscletoneandcoordinationoffinemotormovement.BRAIN:BrainstemandDiencephalonBRAIN:DiencephalonandCerebrumDiencephalon

isconsistsofthefollowing:1.Thalamus–themainsensoryrelaysystem.Italsoinfluencesmoodandregistersanunlocalizedanduncomfortableperceptionofpain.2.Epithalamus–withpinealbodymayplayanimportantroleinsexualorientation(puberty).3.Hypothalamus–isimportantinmaintainingbalance.Cerebrum–isthelargestpartofthebrainwhichhastwohemispheresdividedintolobes.Thelobesarefrontal,parietal,occipitalandtemporal.Thebrainhasnumerousfoldscalledasgyriandgroovescall