资源描述：
《托福TPO24阅读真题及答案(二).doc》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。
1、以下，是这次环球托福为正在进行托福备考的考友们整理了托福TPO24阅读真题及答案LakeBreathingDuringSleep。我们建议考友们，先做真题，后看答案进行验证自己的正确率。之后，环球托福还会进一步推出托福TPO24阅读真题的做题思路讲解分析，做完真题后，更便于提高托福阅读能力。托福TPO24阅读真题BreathingDuringSleepBreathingDuringSleepOfallthephysiologicaldifferencesinhumansleepcomparedwithwakefulnessthathavebe
2、endiscoveredinthelastdecade,changesinrespiratorycontrolaremostdramatic.Notonlyaretheredifferencesinthelevelofthefunctioningofrespiratorysystems,thereareevenchangesinhowtheyfunction.Movementsoftheribcageforbreathingarereducedduringsleep,makingthecontractionsofthediaphragmmor
3、eimportant.Yetbecauseofthephysicsoflyingdown,thestomachappliesweightagainstthediaphragmandmakesitmoredifficultforthediaphragmtodoitsjob.However,therearemanyotherchangesthataffectrespirationwhenasleep.Duringwakefulness,breathingiscontrolledbytwointeractingsystems.Thefirstisa
4、nautomatic,metabolicsystemwhosecontroliscenteredinthebrainstem.Itsubconsciouslyadjustsbreathingrateanddepthinordertoregulatethelevelsofcarbondioxide(CO2)andoxygen(O2),andtheacid-baseratiointheblood.Thesecondsystemisthevoluntary,behavioralsystem.Itscontrolcenterisbasedinthef
5、orebrain,anditregulatesbreathingforuseinspeech,singing,sighing,andsoon.Itiscapableofignoringoroverridingtheautomatic,metabolicsystemandproducesanirregularpatternofbreathing.DuringNREM(thephaseofsleepinwhichthereisnorapideyemovement)breathingbecomesdeeperandmoreregular,butth
6、ereisalsoadecreaseinthebreathingrate,resultinginlessairbeingexchangedoverall.ThisoccursbecauseduringNREMsleeptheautomatic,metabolicsystemhasexclusivecontroloverbreathingandthebodyuseslessoxygenandproduceslesscarbondioxide.Also,duringsleeptheautomaticmetabolicsystemislessres
7、ponsivetocarbondioxidelevelsandoxygenlevelsintheblood.Twothingsresultfromthesechangesinbreathingcontrolthatoccurduringsleep.First,theremaybeabriefcessationorreductionofbreathingwhenfallingasleepasthesleeperwaxesandwanesbetweensleepandwakefulnessandtheirdifferingcontrolmecha
8、nisms.Second,oncesleepisfullyobtained,thereisanincreaseofcarbondioxideandadecrease
