2016年军考专升本英语模拟

1/82016年军考大专生英语模拟考试时长：120分钟；考试分数：100分一．快速阅读（共10分，每小题1分）Ifitweren'tfornicotine,peoplewouldn'tsmoketobacco.Why?Becauseofthemorethan4000chemicalsintobaccosmoke,nicotineistheprimaryonethatactsonthebrain,alteringpeople'smoods,appetitesandalertnessinwaystheyfindpleasantandbeneficial.Unfortunately,asitiswidelyknown,nicotinehasadarkside:itishighlyaddictive.Oncesmokersbecomehookedonit,theymustgettheirfixofitregularly,sometimesseveraldozentimesaday.Cigarettesmokecontains43knowncarcinogens,whichmeansthatlong-termsmokingcanamounttoadeathsentence.IntheUSalone,420,000Americansdieeveryyearfromtobacco-relatedillnesses.Breakingnicotineaddictionisnoteasy.Eachyear,nearly35millionpeoplemakeaconcertedefforttoquitsmoking.Sadly,lessthan7percentsucceedinabstainingformorethanayear;moststartsmokingagainwithindays.Sowhatisnicotineandhowdoesitinsinuateitselfintothesmoker'sbrainandverybeing?Thenicotinefoundintobaccoisapotentdrugandsmokers,andevensomescientists,sayitofferscertainbenefits.Oneisenhanceperformance.Onestudyfoundthatnon-smokersgivendosesofnicotinetypedabout5percentfasterthantheydidwithoutit.Togreaterorlesserdegrees,usersalsosaynicotinehelpsthemtomaintainconcentration,reduceanxiety,relievepain,andevendampentheirappetites(thushelpinginweightcontrol).Unfortunately,nicotinecanalsoproducedeleteriouseffectsbeyondaddiction.Athighdoses,asareachievedfromtobaccoproducts,itcancausehighbloodpressure,distressintherespiratoryandgastrointestinalsystemsandanincreaseinsusceptibilitytoseizuresandhypothermia.Firstisolatedasacompoundin1828,initspureformnicotineisaclearliquidthatturnsbrownwhenburnedandsmellsliketobaccowhenexposedtoair.Itisfoundinseveralspeciesofplants,includingtobaccoand,perhapssurprisingly,intomatoes,potatoes,andeggplant(thoughinextremelylowquantitiesthatarepharmacologicallyinsignificantforhumans).Assimpleasitlooks,thecigaretteishighlyengineerednicotinedeliverydevice.Forinstance,whentobaccoresearchersfoundthatmuchofthenicotineinacigarettewasn'treleasedwhenburnedbutratherremainedchemicallyboundwithinthetobaccoleaf,theybeganaddingsubstancessuchasammoniatocigarettetobaccotoreleasemorenicotine.Ammoniahelpskeepnicotineinitsbasicform,whichismorereadilyvaporisedbytheintenseheatoftheburningcigarettethantheacidicform.MostcigarettesforsaleintheUStodaycontain10milligramsormoreofnicotine.Byinhalingsmokefromalightedcigarette,theaveragesmokertakes1or2milligramsofvaporisednicotinepercigarette.Todayweknowthatonlyaminisculeamountofnicotineisneededtofueladdiction.Researchshowsthatmanufacturerswouldhavetocutnicotinelevelsinatypicalcigaretteby95%toforestallitspowertoaddict.Whenasmokerpuffsonalightedcigarette,smoke,includingvaporisednicotine,isdrawnintothemouth.Theskinandliningofthemouthimmediatelyabsorbsomenicotine,buttheremainderflowsstraightdownintothelungs,whereiteasilydiffusesintothebloodvesselsliningthelungwalls.Thebloodvesselscarrythenicotinetotheheart,whichthenpumpsitdirectlytothebrain.Whilemostoftheeffectsasmokerseeksoccurinthebrain,thehearttakesahitaswell.Studieshaveshownthatasmoker'sfirstcigaretteofthedaycanincreasehisorherheartrateby10to20beatsaminute.Scientistshavefoundthatasmokedsubstancereachesthebrainmorequicklythanoneswallowed,snorted(suchascocainepowder)oreveninjected.Indeed,anicotinemoleculeinhaledinsmokewillreachthebrainwithin10seconds.Thenicotinetravelsthroughbloodvessels,whichbranchoutintocapillarieswithinthebrain.Capillariesnormallycarrynutrientsbuttheyreadilyaccommodatenicotinemoleculesaswell.Onceinsidethebrain,nicotine,likemostaddictivedrugs,triggersthereleaseofchemicalsassociatedwitheuphoriaandpleasure.Justasitmovesrapidlyfromthelungsintothebloodstream,nicotinealsoeasilydiffusesthroughcapillarywalls.Itthenmigratestothespacessurroundingneurons—ganglioncellsthattransmitnerveimpulsesthroughoutthenervoussystem.Theseimpulsesarethebasisforourthoughts,feelings,andmoods.Totransmitnerveimpulsestoitsneighbor,a2/8neuronereleaseschemicalmessengersknownasneurotransmitters.Likenicotinemolecules,theneurotransmittersdriftintotheso-calledsynapticspacebetweenneurones,readytolatchontothereceivingneuroneandthusdeliverachemical“message”thattriggersanelectricalimpulse.Theneurotransmittersbindontoreceptorsonthesurfaceoftherecipientneurone.Thisopenschannelsinthecellsurfacethroughwhichenterions,orchargedatoms,ofsodium.Thisgeneratesacurrentacrossthemembraneofthereceivingcell,whichcompletesdeliveryofthe“message”.Anaccomplishedmimic,nicotinecompeteswiththeneurotransmitterstobindtothereceptors.Itwinsand,likethevanquishedchemical,opensionchannelsthatletsodiumionsintothecell.Butthere'salotmorenicotinearoundthantheoriginaltransmitter,soamuchlargercurrentspreadsacrossthemembrane.Thisbiggercurrentcausesincreasedelectricalimpulsestotravelalongcertainneurones.Withrepeatedsmoking,theneuronesadapttothisincreasedelectricalactivity,andthesmokerbecomesdependentonthenicotine.问题1~7，符合文章内容的填写Y；不符合文章内容的填写N；文章未提及的填写NG。问题8~10，根据文章内容补充句子。1.Althoughnicotineisprobablythewell-knownchemicalincigarettes,itisnotnecessarilytheonethatchangesthepsycheofthesmokerwhencigarettesare