3 The Biological bases of Beha.ppt

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1、Chapter3TheBiologicalbasesofBehaviorCommunicationintheNervousSystemHardware:Glia–structuralsupportandinsulationNeurons–communicationSoma–cellbodyDendrites–receiveAxon–transmitawayFig3.1-Structureoftheneuron.Neuronsarethecommunicationlinksofthenervous

2、system.Thisdiagramhighlightsthekeypartsofaneuron,includingspecializedreceptorareas(dendrites),thecellbody(soma),theaxonfiberalongwhichimpulsesaretransmitted,andtheterminalbuttons,whichreleasechemicalmessengersthatcarrysignalstootherneurons.Neuronsvar

3、yconsiderablyinsizeandshapeandareusuallydenselyinterconnected.NeuralCommunication:InsulationandInformationTransferMyelinsheath–speedsuptransmissionTerminalButton–endofaxon;secretesneurotransmittersNeurotransmitters–chemicalmessengersSynapse–pointatwh

4、ichneuronsinterconnectTheNeuralImpulse:ElectrochemicalBeginningsHodgkin&Huxley(1952)-giantsquidFluidsinsideandoutsideneuronElectricallychargedparticles(ions)Neuronatrest–negativechargeoninsidecomparedtooutside-70millivolts–restingpotentialTheNeuralIm

5、pulse:TheActionPotentialStimulationcausescellmembranetoopenbrieflyPositivelychargedsodiumionsflowinShiftinelectricalchargetravelsalongneuronTheActionPotentialAll–or–nonelawFig3.2-Theneuralimpulse.Theelectricchargeofaneuroncanbemeasuredwithapairofelec

6、trodesconnectedtoanoscilloscope.(a)Atrest,theneuronislikeatinywetbatterywitharestingpotentialofabout–70millivolts.(b)Whenaneuronisstimulated,asharpjumpinitselectricpotentialoccurs,resultinginaspikeontheoscilloscoperecordingoftheneuron’selectricalacti

7、vity.Thischangeinvoltage,calledanactionpotential,travelsalongtheaxon.(c)Biochemicalchangespropeltheactionpotentialalongtheaxon.Anactionpotentialbeginswhensodiumgatesinthemembraneofanaxonopen,permittingpositivelychargedsodiumionstoflowintotheaxon.(d)B

8、ythepeakoftheactionpotential,thesodiumgateshaveclosed,butpotassiumgateshaveopenedtoletpotassiumionsflowoutward.Atthenextpointalongtheaxonmembrane,sodiumgatesopenandtheprocessisrepeated,thusallowingtheactionpotentialtoflowalongtheaxon.(e)Thisblowupoft