4 级考前最新命制试卷三

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4级考前最新命制试卷三PartIWriting(30minutes)Directions:Forthispart,youareallowed30minutestowriteashortessayentitledTheImportanceofSettingAnAimbycommentingonR.Peters’remark,“Haveanaiminlife,oryourenergieswillbeallwasted.”Youshouldwriteatleast120wordsbutnomorethan180words.

TheImportanceofSettingAnAim________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

PartIIReadingComprehension(SkimmingandScanning)(15minutes)

Directions:Inthispart,youwillhave15minutestogooverthepassagequicklyandanswerthequestionson

AnswerSheet1.Forquestions1-7,choosethebestanswerfromthefourchoicesmarkedA),B),C)andD).Forquestions8-10,completethesentenceswiththeinformationgiveninthepassage.

TheHumanBrainThebrainisthemostcomplexorganinhumanbody.Itproducesoureverythought,action,memory,feelingandexperienceoftheworld.Thisjelly-likemassoftissue,weighinginaround1.4kilograms,containsastaggeringonehundredbillionnervecells,orneurons(神经 元).Thecomplexityoftheconnectivitybetweenthesecellsismind-boggling(令人难以置信的).Eachneuroncanmakecontactwiththousandsoreventensofthousandsofothers,viatinystructurescalled

synapses(突触).Ourbrainsformamillionnewconnectionsforeverysecondofourlives.Thepatternandstrengthofthe

connectionsisconstantlychangingandnotwobrainsarealike.Itisinthesechangingconnectionsthatmemoriesarestored,habitslearnedandpersonalitiesshaped,byreinforcingcertainpatternsofbrainactivities,andlosingothers.GreyMatterandWhiteMatterWhilepeopleoftenspeakoftheir“greymatter”,thebrainalsocontainswhitematter.Thegreymatteristhecellbodiesoftheneurons,whilethewhitematteristhebranchingnetworkofthread-liketendrils—calleddendritesandaxons—thatspreadoutfromthecellbodiestoconnecttootherneurons.Butthebrainalsohasanother,evenmorenumeroustypeofcell,calledglial(神经 胶质的)cells.Theseoutnumberneuronsovertentimes.Oncethoughttobesupportcells,theyarenowknowntoamplifyneuralsignalsandtobeasimportantasneuronsinmentalcalculations.Therearemanydifferenttypesofneuron,onlyoneofwhichisuniquetohumansandtheothergreatapes,theso-calledspindlecells.Brainstructureisshapedpartlybygenes,butlargelybyexperience.Onlyrecentlyitwasdiscoveredthatnewbraincellsarebeingbornthroughoutourlives—aprocesscalledneurogenesis.Thebrainhasburstsofgrowthandthenperiodsofconsolidation,whenexcessconnectionsareremoved.Themostnotableburstsareinthefirsttwoorthreeyearsoflife,duringpuberty,andalsoafinalburstinyoungadulthood.Howabrainagesalsodependsongenesandlifestyletoo.Exercisingthebrainandgivingittherightdietcanbejustasimportantasitisfortherestofthebody.ChemicalMessengersTheneuronsinourbrainscommunicateinavarietyofways.Signalspassbetweenthembythereleaseandcaptureofneurotransmitterandneuromodulatorchemicals,suchasglutamate,dopamine,acetylcholine,noradrenalin,serotoninandendorphins.Someneurochemicalsworkinthesynapse,passingspecificmessagesfromreleasesitestocollectionsites,calledreceptors.Othersalsospreadtheirinfluencemorewidely,likearadiosignal,makingwholebrainregionsmoreorlesssensitive.Theseneurochemicalsaresoimportantthatdeficienciesinthemarelinkedtocertaindiseases.Forexample,alossofdopamineinthebasalganglia(基底神经 节),whichcontrolsmovements,leadstoParkinson’sdisease.Itcanalsoincreasesusceptibilitytoaddictionbecauseitmediatesoursensationsofrewardandpleasure.Similarly,adeficiencyinserotonin,usedbyregionsinvolvedinemotion,canbelinkedtodepressionormooddisorders,andthelossofacetylcholineinthecerebralcortex(大脑皮层)ischaracteristicofAlzheimer’sdisease.BrainScanningWithinindividualneurons,signalsareformedbyelectrochemicalpulses.Collectively,thiselectricalactivitycanbedetectedoutsidethescalpbyanelectroencephalogram(EEG).Thesesignalshavewave-likepatterns,whichscientistsclassifyfromalpha(commonwhilewearerelaxingorsleeping),throughtogamma(activethought).Whenthisactivitygoesawry(错误的),itiscalledaseizure.Someresearchersthinkthatsynchronisingtheactivityindifferentbrainregionsisimportantinperception.Otherwaysofimagingbrainactivityareindirect.Functionalmagneticresonanceimaging(FMRI)orpositronemissiontomography(PET)monitorsbloodflow.MRIscans,computedtomography(CT)scansanddiffusiontensorimages(DTI)usethemagneticsignaturesofdifferenttissues,X-rayabsorption,orthemovementofwatermoleculesinthosetissues,toimagethebrain.Thesescanningtechniqueshaverevealedwhichpartsofthebrainareassociatedwithwhichfunctions.Examplesincludeactivitiesrelatedtosensations,movement,libido,choices,regrets,motivationsandevenracism.However,someexpertsarguethatweputtoomuchtrustintheseresultsandthattheyraiseprivacyissues.Beforescanningtechniqueswerecommon,researchersreliedonpatientswithbraindamagecausedbystrokes,headinjuriesorillnesses,todeterminewhichbrainareasarerequiredforcertainfunctions.SomeStructuresinMindThemostobviousanatomicalfeatureofourbrainsistheundulatingsurfaceofthecerebrum(大脑)—thedeepcleftsareknownassulcianditsfoldsaregyri.Thecerebrumisthelargestpartofourbrainandislargelymadeupofthetwocerebralhemispheres.Itisthemostevolutionarilyrecentbrainstructure,dealingwithmorecomplexcognitivebrainactivities.Itisoftensaidthattherighthemisphereismorecreativeandemotionalwhiletheleftdealswithlogic,buttherealityismorecomplex.Nonetheless,thesidesdohavesomespecialization,withtheleftdealingwithspeechandlanguage,