【单选题】 Guitarlike instruments have exist since ancient times, but the first written mention of the guitar itself is from the fourteenth century.
【单选题】 Fuel is (any) substance or material (that reacts) chemically (with) another substance or material toproduce (hot).
A．any
B．that reacts
C．with
D．hot
A．any
B．that reacts
C．with
D．hot
【单选题】 The first transatlantic telephone cable system was not established _______ 1956.
A．while
B．until
C．on
D．when
A．while
B．until
C．on
D．when
【单选题】 On September 6, 1996, civil rights (activist) Rosa Parks (was awarded) the Presidential Medal of Freedom, the (highest )honor the United States government gives (to civilian).
A．activist
B．was awarded
C．highest
D．to civilian
A．activist
B．was awarded
C．highest
D．to civilian
【单选题】 It can be inferred from the passage that one reason that sociologists may become frustrated with questionnaires is that
A．( respondents often do not complete and return questionnaires
B．( questionnaires are often difficult to read
C．( questionnaires are expensive and difficult to distribute
D．( respondents are too eager to supplement questions with their own opinions
A．( respondents often do not complete and return questionnaires
B．( questionnaires are often difficult to read
C．( questionnaires are expensive and difficult to distribute
D．( respondents are too eager to supplement questions with their own opinions
【单选题】 What does the passage mainly discuss
A．( How insects use pheromones to communicate
B．( How pheromones are produced by insects
C．( Why analyzing insect pheromones is difficult
D．( The different uses of pheromones among various insect species
A．( How insects use pheromones to communicate
B．( How pheromones are produced by insects
C．( Why analyzing insect pheromones is difficult
D．( The different uses of pheromones among various insect species
【单选题】rEADing 3 "groupDECision mAking"
ADvAntAgEs oF groupDECision mAking
→CommittEEs, tAsk ForCEs, AnD AD hoC groups ArE FrEquEntly AssignED to iDEntiFy AnD rECommEnD DECision AltErnAtivEs or, in somE CAsEs, to ACtuAlly mAkE importAnt DECisions. in EssEnCE, A group is A tool thAt CAn FoCus thE ExpEriEnCE AnD ExpErtisE oF sEvErAl pEoplE on A pArtiCulAr proBlEm or situAtion. thus, A group oFFErs thE ADvAntAgE oF grEAtEr totAl knowlEDgE. groups ACCumulAtE morE inFormAtion, knowlEDgE, AnD FACts thAn inDiviDuAls AnD oFtEn ConsiDEr morE AltErnAtivEs.EACh pErson in thE group is ABlE to DrAw on his or hEr uniquE EDuCAtion, ExpEriEnCE, insights, AnD othEr rEsourCEs AnD ContriButE thosE to thE group. thE vAriED BACkgrounDs, trAining lEvEls, AnD ExpErtisE oF group mEmBErs Also hElp ovErComE tunnEl vision By EnABling thE group to viEw thE proBlEm in morE thAn onE wAy.
→ pArtiCipAtion in group DECision mAking usuAlly lEADs to highEr mEmBEr sAtisFACtion. pEoplE tEnD to ACCEpt A DECision morE rEADily AnD to BE BEttEr sAtisFiED with it whEn thEy hAvE pArtiCipAtED in mAking thAt DECision. in ADDition, pEoplE will BEttEr unDErstAnD AnD BE morE CommittED to A DECision in whiCh thEy hAvE hAD A sAy thAn to A DECision mADE For thEm.As A rEsult, suCh A DECision is morE likEly to BE implEmEntED suCCEssFully.
DisADvAntAgEs oF groupDECision mAking
→ whilE groups hAvE mAny potEntiAl BEnEFits, wE All know thAt thEy CAn Also BE FrustrAting.
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onE oBvious DisADvAntAgE oF group DECision mAking is thE timErEquirED to mAkE A DECision.
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thE timE nEEDED For group DisCussion AnD thE AssoCiAtED Compromising AnD sElECting oF A DECision AltErnAtivE CAn BE ConsiDErABlE.
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timE Costs monEy, so A wAstE oF timE BEComEs A DisADvAntAgE iF A DECision mADE By A group CoulD hAvE BEEn mADE just As EFFECtivEly By An inDiviDuAl working AlonE.
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ConsEquEntly, group DECisions shoulD BE AvoiDED whEn spEED AnD EFFiCiEnCy ArE thE primAry ConsiDErAtions.
A、sEConD DisADvAntAgE is thAt thE group DisCussion mAy BE DominAtED By An inDiviDuAl or suBgroup.EFFECtivEnEss CAn BE rEDuCED iF onE inDiviDuAl, suCh As thE group lEADEr, DominAtEs thE DisCussion By tAlking too muCh or BEing ClosED to othEr points oF viEw. somE group lEADErs try to Control thE group AnD proviDE thE mAjor input. suCh DominAnCE CAn stiFlE othEr group mEmBErs’ willingnEss to pArtiCipAtE AnD CoulD CAusE DECision AltErnAtivEs to BE ignorED or ovErlookED、All group mEmBErs nEED to BE EnCourAgED AnD pErmittED to ContriButE.
→AnothEr DisADvAntAgE oF group DECision mAking is thAt mEmBErs mAy BE lEss ConCErnED with thE group’s goAls thAn with thEir own pErsonAl goAls. thEy mAy BEComE so siDEtrACkED in trying to win An ArgumEnt thAt thEy ForgEt ABout group pErFormAnCE. on thE othEr hAnD, A group mAy try too hArD to CompromisE AnD ConsEquEntly mAy not mAkE optimAl DECisions. somEtimEs this stEms From thE DEsirE to mAintAin FriEnDships AnD AvoiD DisAgrEEmEnts. oFtEn groups ExErt trEmEnDous soCiAl prEssurE on inDiviDuAls to ConForm to EstABlishED or ExpECtED pAttErns ot BEhAvior.EspECiAlly whEn thEy ArE DEAling with importAnt AnD ControvErsiAl issuEs, intErACting groups mAy BE pronE to A phEnomEnon CAllED groupthink.
→ groupthink is An AgrEEmEnt-At-Any-Cost mEntAlity thAt rEsults in inEFFECtivE group DECision mAking. it oCCurs whEn groups ArE highly CohEsivE, hAvE highly DirECtivE lEADErs, ArE insulAtED so thEy hAvE no ClEAr wAys to gEt oBjECtivE inFormAtion, AnD—BECAusE thEy lACk outsiDE inFormAtion—hAvE littlE hopE thAt A BEttEr solution might BE FounD thAn thE onE proposED By thE lEADEr or othEr inFluEntiAl group mEmBErs. thEsE ConDitions Fo
ADvAntAgEs oF groupDECision mAking
→CommittEEs, tAsk ForCEs, AnD AD hoC groups ArE FrEquEntly AssignED to iDEntiFy AnD rECommEnD DECision AltErnAtivEs or, in somE CAsEs, to ACtuAlly mAkE importAnt DECisions. in EssEnCE, A group is A tool thAt CAn FoCus thE ExpEriEnCE AnD ExpErtisE oF sEvErAl pEoplE on A pArtiCulAr proBlEm or situAtion. thus, A group oFFErs thE ADvAntAgE oF grEAtEr totAl knowlEDgE. groups ACCumulAtE morE inFormAtion, knowlEDgE, AnD FACts thAn inDiviDuAls AnD oFtEn ConsiDEr morE AltErnAtivEs.EACh pErson in thE group is ABlE to DrAw on his or hEr uniquE EDuCAtion, ExpEriEnCE, insights, AnD othEr rEsourCEs AnD ContriButE thosE to thE group. thE vAriED BACkgrounDs, trAining lEvEls, AnD ExpErtisE oF group mEmBErs Also hElp ovErComE tunnEl vision By EnABling thE group to viEw thE proBlEm in morE thAn onE wAy.
→ pArtiCipAtion in group DECision mAking usuAlly lEADs to highEr mEmBEr sAtisFACtion. pEoplE tEnD to ACCEpt A DECision morE rEADily AnD to BE BEttEr sAtisFiED with it whEn thEy hAvE pArtiCipAtED in mAking thAt DECision. in ADDition, pEoplE will BEttEr unDErstAnD AnD BE morE CommittED to A DECision in whiCh thEy hAvE hAD A sAy thAn to A DECision mADE For thEm.As A rEsult, suCh A DECision is morE likEly to BE implEmEntED suCCEssFully.
DisADvAntAgEs oF groupDECision mAking
→ whilE groups hAvE mAny potEntiAl BEnEFits, wE All know thAt thEy CAn Also BE FrustrAting.
A、sEConD DisADvAntAgE is thAt thE group DisCussion mAy BE DominAtED By An inDiviDuAl or suBgroup.EFFECtivEnEss CAn BE rEDuCED iF onE inDiviDuAl, suCh As thE group lEADEr, DominAtEs thE DisCussion By tAlking too muCh or BEing ClosED to othEr points oF viEw. somE group lEADErs try to Control thE group AnD proviDE thE mAjor input. suCh DominAnCE CAn stiFlE othEr group mEmBErs’ willingnEss to pArtiCipAtE AnD CoulD CAusE DECision AltErnAtivEs to BE ignorED or ovErlookED、All group mEmBErs nEED to BE EnCourAgED AnD pErmittED to ContriButE.
→AnothEr DisADvAntAgE oF group DECision mAking is thAt mEmBErs mAy BE lEss ConCErnED with thE group’s goAls thAn with thEir own pErsonAl goAls. thEy mAy BEComE so siDEtrACkED in trying to win An ArgumEnt thAt thEy ForgEt ABout group pErFormAnCE. on thE othEr hAnD, A group mAy try too hArD to CompromisE AnD ConsEquEntly mAy not mAkE optimAl DECisions. somEtimEs this stEms From thE DEsirE to mAintAin FriEnDships AnD AvoiD DisAgrEEmEnts. oFtEn groups ExErt trEmEnDous soCiAl prEssurE on inDiviDuAls to ConForm to EstABlishED or ExpECtED pAttErns ot BEhAvior.EspECiAlly whEn thEy ArE DEAling with importAnt AnD ControvErsiAl issuEs, intErACting groups mAy BE pronE to A phEnomEnon CAllED groupthink.
→ groupthink is An AgrEEmEnt-At-Any-Cost mEntAlity thAt rEsults in inEFFECtivE group DECision mAking. it oCCurs whEn groups ArE highly CohEsivE, hAvE highly DirECtivE lEADErs, ArE insulAtED so thEy hAvE no ClEAr wAys to gEt oBjECtivE inFormAtion, AnD—BECAusE thEy lACk outsiDE inFormAtion—hAvE littlE hopE thAt A BEttEr solution might BE FounD thAn thE onE proposED By thE lEADEr or othEr inFluEntiAl group mEmBErs. thEsE ConDitions Fo
【单选题】wAtErAnD、liFE、on mArs
1thE prEsEnCE or ABsEnCE oF wAtEr hAs A DirECt BEAring on thE possiBility oF liFE on othEr plAnEts. in thE ninEtEEnth CEntury, it wAs Commonly ACCEptED thAt liFE, pErhAps EvEn intElligEnt liFE, wAs wiDEsprEAD in thE solAr systEm, AnD mArs wAs An oBvious tArgEt in thE sEArCh For liFE. nEw photogrAphiC tEChnology oFFErED A wAy For AstronomErs to lEArn morE ABout thE rED plAnEt. in 1888, itAliAn AstronomEr giovAnni sChiApArElli proDuCED imAgEs thAt showED A nEtwork oF long, thin, DArk linEs Crossing thE surFACE oF mArs. hE CAllED thEsE FEAturEs CAnAli in itAliAn, whiCh BECAmE "CAnAls" or "ChAnnEls" inEnglish. thE strAngE AppEArAnCE oF thE CAnAls suggEstED to somE sCiEntists thAt thEy hAD BEEn FormED ArtiFiCiAlly rAthEr thAn nAturAlly. thE mystEry DEEpEnED whEn sChiApArElli oBsErvED thAt mAny oF thE CAnAls in thE photogrAphs wErE ACtuAlly DouBlE.
2othEr photogrAphiC imAgEs oF mArs rEvEAlED its sEAsonAlly ChAnging polAr iCE CAps AnD FEAturEs thAt AppEArED to BE AnCiEnt islAnDs loCAtED in whAt wAs now A Dry strEAmBED、whEn thE islAnDs wErE First DisCovErED, somE sCiEntists spECulAtED thAt A thiCk wAtEr-lADEn AtmosphErE CApABlE oF gEnErAting hEAvy rAins hAD onCE ExistED on mArs. howEvEr, othErs rEmAinED unConvinCED oF thE prEsEnCE oF wAtEr. thEn, in 1963, A tEAm oF AstronomErs oBtAinED A gooD photogrAphiC plAtE oF thE nEAr-inFrArED spECtrum oF mArs. thE photogrAph showED thAt, FAintly But DEFinitEly, wAtEr vApor linEs CoulD BE sEEn. this photogrAph EstABlishED thAt thErE rEAlly wAs wAtEr on mArs, though thE Amount wAs vEry smAll. toDAy, thE prEsEnCE oF wAtEr vApor in thE mArtiAn AtmosphErE is gEnErAlly ACCEptED, As is thE BEliEF thAt thE AtmosphErE wAs onCE muCh DEnsEr thAn it is now, with A muCh grEAtEr ABunDAnCE oF wAtEr vApor.
3thE surFACE oF mArs is Dry toDAy, But it DoEs ContAin signiFiCAnt Amounts oF iCE AnD signs thAt liquiD wAtEr onCE FlowED ovEr thE plAnEt.All oF thE loCAtions whErE EviDEnCE oF wAtEr hAs BEEn FounD ArE AnCiEnt, proBABly FormED vEry EArly in mArtiAn history.DAtA trAnsmittED From spACECrAFt on mArs in 2004 hAvE rEvEAlED thAt wAtEr wAs onCE Common ACross A vAst rEgion oF thE plAnEt, possiBly As shAllow lAkEs or sEAs thAt DriED out AnD thEn FillED up AgAin. thErE ArE signs thAt thE winD BlEw DEBris ArounD During Dry stAgEs. thEsE sEAs AnD lAkEs ExtEnDED ACross hunDrEDs oF thousAnDs oF squArE milEs, CrEAting hABitABlE ConDitions During long strEtChEs oF timE Billions oF yEArs Ago.
4 EviDEnCE oF wAtEr inCluDEs thE prEsEnCE oF vArious minErAls known As EvAporAtEs, DEposits lEFt BEhinD whEn liquiD wAtEr turns to vApor. smAll ArEAs oF minErAl DEposits hAvE BEEn FounD in vAllEs mArinEris, A hugE holE on mArs thAt is lArgEr thAn thE grAnDCAnyon onEArth. thE minErAls thErE ContAin wAtEr, so thEy hAD to BE FormED in thE prEsEnCE oF wAtEr. gEologiC rEsEArCh hAs Also turnED up ClAy AnD gypsum DEposits thAt wErE FormED By wAtEr in thE soil. roCks thAt ClEArly FormED in wAtEr ExtEnD throughout 300 mEtErs oF lAyErED mAtEriAls in sEvErAl loCAtions ACross thE mArtiAn plAins. thE lAyErs wErE Built up ovEr timE, whiCh mEAns wAtEr wAs prEsEnt, At lEAst tEmporArily, For ExtEnDED pErioDs on AnCiEnt mArs.
5 BEsiDEs thE iCE pACks At mArs’s polEs, AstronomErs hAvE DisCovErED A FrozEn sEA nEAr its EquAtor. this FrozEn sEA is thE sizE oF thE north sEA onEArth AnD AppEArs similAr to thE iCE pACks onAntArCtiCA、sCiEntists hAvE Also DEtECtED EviDEnCE oF lAvA Flows 20 million yEArs Ago As wEll As signs thAt somE volCAnoEs mAy still BE ACtivE. sEvErAl rECEntly FormED volCAniC ConEs nEAr mArs’s north polE inDiCAtE thAt thE plAnEt’s CorE mAy intErACt with thE surFACE, mEAning thErE wAs Both wArmth AnD moisturE in thE rECEnt pAs-CirCumstAnCEs thAt might hAvE supportED liFE.
6liquiD wAtEr is thE kEy ingrEDiEnt For liFE As wE know it. oF All thE othEr plAnEts in thE solAr systEm, mArs is most likEEArth. thE FACt th
1thE prEsEnCE or ABsEnCE oF wAtEr hAs A DirECt BEAring on thE possiBility oF liFE on othEr plAnEts. in thE ninEtEEnth CEntury, it wAs Commonly ACCEptED thAt liFE, pErhAps EvEn intElligEnt liFE, wAs wiDEsprEAD in thE solAr systEm, AnD mArs wAs An oBvious tArgEt in thE sEArCh For liFE. nEw photogrAphiC tEChnology oFFErED A wAy For AstronomErs to lEArn morE ABout thE rED plAnEt. in 1888, itAliAn AstronomEr giovAnni sChiApArElli proDuCED imAgEs thAt showED A nEtwork oF long, thin, DArk linEs Crossing thE surFACE oF mArs. hE CAllED thEsE FEAturEs CAnAli in itAliAn, whiCh BECAmE "CAnAls" or "ChAnnEls" inEnglish. thE strAngE AppEArAnCE oF thE CAnAls suggEstED to somE sCiEntists thAt thEy hAD BEEn FormED ArtiFiCiAlly rAthEr thAn nAturAlly. thE mystEry DEEpEnED whEn sChiApArElli oBsErvED thAt mAny oF thE CAnAls in thE photogrAphs wErE ACtuAlly DouBlE.
2othEr photogrAphiC imAgEs oF mArs rEvEAlED its sEAsonAlly ChAnging polAr iCE CAps AnD FEAturEs thAt AppEArED to BE AnCiEnt islAnDs loCAtED in whAt wAs now A Dry strEAmBED、whEn thE islAnDs wErE First DisCovErED, somE sCiEntists spECulAtED thAt A thiCk wAtEr-lADEn AtmosphErE CApABlE oF gEnErAting hEAvy rAins hAD onCE ExistED on mArs. howEvEr, othErs rEmAinED unConvinCED oF thE prEsEnCE oF wAtEr. thEn, in 1963, A tEAm oF AstronomErs oBtAinED A gooD photogrAphiC plAtE oF thE nEAr-inFrArED spECtrum oF mArs. thE photogrAph showED thAt, FAintly But DEFinitEly, wAtEr vApor linEs CoulD BE sEEn. this photogrAph EstABlishED thAt thErE rEAlly wAs wAtEr on mArs, though thE Amount wAs vEry smAll. toDAy, thE prEsEnCE oF wAtEr vApor in thE mArtiAn AtmosphErE is gEnErAlly ACCEptED, As is thE BEliEF thAt thE AtmosphErE wAs onCE muCh DEnsEr thAn it is now, with A muCh grEAtEr ABunDAnCE oF wAtEr vApor.
3thE surFACE oF mArs is Dry toDAy, But it DoEs ContAin signiFiCAnt Amounts oF iCE AnD signs thAt liquiD wAtEr onCE FlowED ovEr thE plAnEt.All oF thE loCAtions whErE EviDEnCE oF wAtEr hAs BEEn FounD ArE AnCiEnt, proBABly FormED vEry EArly in mArtiAn history.DAtA trAnsmittED From spACECrAFt on mArs in 2004 hAvE rEvEAlED thAt wAtEr wAs onCE Common ACross A vAst rEgion oF thE plAnEt, possiBly As shAllow lAkEs or sEAs thAt DriED out AnD thEn FillED up AgAin. thErE ArE signs thAt thE winD BlEw DEBris ArounD During Dry stAgEs. thEsE sEAs AnD lAkEs ExtEnDED ACross hunDrEDs oF thousAnDs oF squArE milEs, CrEAting hABitABlE ConDitions During long strEtChEs oF timE Billions oF yEArs Ago.
4 EviDEnCE oF wAtEr inCluDEs thE prEsEnCE oF vArious minErAls known As EvAporAtEs, DEposits lEFt BEhinD whEn liquiD wAtEr turns to vApor. smAll ArEAs oF minErAl DEposits hAvE BEEn FounD in vAllEs mArinEris, A hugE holE on mArs thAt is lArgEr thAn thE grAnDCAnyon onEArth. thE minErAls thErE ContAin wAtEr, so thEy hAD to BE FormED in thE prEsEnCE oF wAtEr. gEologiC rEsEArCh hAs Also turnED up ClAy AnD gypsum DEposits thAt wErE FormED By wAtEr in thE soil. roCks thAt ClEArly FormED in wAtEr ExtEnD throughout 300 mEtErs oF lAyErED mAtEriAls in sEvErAl loCAtions ACross thE mArtiAn plAins. thE lAyErs wErE Built up ovEr timE, whiCh mEAns wAtEr wAs prEsEnt, At lEAst tEmporArily, For ExtEnDED pErioDs on AnCiEnt mArs.
5 BEsiDEs thE iCE pACks At mArs’s polEs, AstronomErs hAvE DisCovErED A FrozEn sEA nEAr its EquAtor. this FrozEn sEA is thE sizE oF thE north sEA onEArth AnD AppEArs similAr to thE iCE pACks onAntArCtiCA、sCiEntists hAvE Also DEtECtED EviDEnCE oF lAvA Flows 20 million yEArs Ago As wEll As signs thAt somE volCAnoEs mAy still BE ACtivE. sEvErAl rECEntly FormED volCAniC ConEs nEAr mArs’s north polE inDiCAtE thAt thE plAnEt’s CorE mAy intErACt with thE surFACE, mEAning thErE wAs Both wArmth AnD moisturE in thE rECEnt pAs-CirCumstAnCEs thAt might hAvE supportED liFE.
6liquiD wAtEr is thE kEy ingrEDiEnt For liFE As wE know it. oF All thE othEr plAnEts in thE solAr systEm, mArs is most likEEArth. thE FACt th
【单选题】An unconsolidated aggregate of silt particles is also termed silt, ___________ a consolidated aggregate is called siltstone.
A、which
B．why
C．whereas
D．whether
A、which
B．why
C．whereas
D．whether
【单选题】ioDinE AnD goitEr
ioDinE is A wEll-known ExAmplE oF A trACE minErAl whosE lACk in thE BoDy CrEAtEs An EAsily trEAtED DisEAsE. whEn thE thyroiD glAnD is not suppliED with suFFiCiEnt ioDinE to mAnuFACturE hormonEs, it EnlArgEs AnD Forms A goitEr or swElling oF thE nECk.At thE sAmE timE othEr symptoms, suCh As FAtiguE AnD sluggishnEss, wEight gAin, ColDnEss oF thE BoDy, AnD DEprEssion, mAy oCCur.
in thE unitED stAtEs goitEr wAs First notED in thE grEAt lAkEs rEgion, whErE in thE 1930s, As mAny As 40 pErCEnt oF thE pEoplE in somE ArEAs hAD goitEr, DuE mAinly to ioDinE-DEFiCiEnt soil. this sCArCity hAD BEEn CAusED By iCE AgE glACiErs mElting AnD wAshing thE ioDinE out oF thE soil.
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thE inhABitAnts oF mountAinous rEgions oFEuropE hAD suFFErED From ioDinE DEFiCiEnCy For CEnturiEs For similAr rEAsons.
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it wAs DisCovErED in thE AlpinE rEgion oF switzErlAnD in thE ninEtEEnth CEntury thAt in ArEAs in whiCh thE Drinking wAtEr ContAinED lEss thAn 0.5 miCrogrAms oF ioDinE pEr litEr thErE wAs A high inCiDEnCE oF goitEr.
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in ContrAst to mountAinous or inlAnD rEgions, ArEAs By oCEAns or in thE viCinity oF oCEAn BrEEzEs usuAlly ContAin Enough ioDinE to prEvEnt this AFFliCtion.
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As A FAirly ACCurAtE rulE oF thumB, iF A mAp is DrAwn showing thE pArts oF thE worlD whErE thE wAtEr supply is DEFiCiEnt in ioDinE AnD thEn supErimposED on A mAp showing thE ArEAs whErE thE inhABitAnts suFFEr From goitEr, thE two mAppED ArEAs CoinCiDE.
to unDErstAnD how ioDinE DEFiCiEnCy lEADs to goitEr, it is nECEssAry to look At thE unDErlying physiology oF thE thyroiD glAnD、thE humAn thyroiD glAnD is thE only plACE in thE BoDy whErE ioDinE is storED, AnD it rEquirEs A DAily supply oF ABout 150 miCrogrAms oF ioDinE EntEring thE BoDy. whEn FooD or wAtEr is DigEstED, thE ioDinE it ContAins is EithEr tAkEn up By thE thyroiD or EliminAtED From thE BoDy through thE kiDnEys into thE urinE. whEn suppliEs ArE low, thE kiDnEys still EliminAtE ioDinE From thE BoDy so thE CApACity oF thE thyroiD to prEsErvE An ADEquAtE supply oF rAw mAtEriAl is thrEAtEnED、
thE thyroiD glAnD Consists oF thousAnDs oF BAlls oF CElls, CAllED thyroiD vEsiClEs, whiCh EnClosE A spACE FillED with A jEllylikE protEin CAllED thyrogloBulin. thEsE CElls hAvE An ExtrAorDinAry ABility to trAp ioDinE From thE BlooDstrEAm, AnD thE EFFiCiEnCy oF this trAp CAn BE inCrEAsED iF thE Amount oF ioDinE in thE BlooD CirCulAtion DECrEAsEs. onCE thE ioDinE is trAppED By thE thyroiD vEsiClEs it pAssEs into thE thyrogloBulin, whErE thE ACtuAl mAnuFACturE oF two kinDs oF thyroiD hormonEs tAkEs plACE. thE hormonEs ArE storED hErE until thEy trAvEl BACk through thE thyroiD vEsiClEs to EntEr thE BlooDstrEAm. thE thyroiD hormonEs ArE thEn tAkEn to EvEry pArt oF thE BoDy whErE thEy inFluEnCE thE rAtE At whiCh thE ChEmiCAl proCEssEs oF EvEry CEll proCEED、thEy hAvE A pErvAsivE EFFECt on thE Control oF oxygEn Consumption AnD hEAt proDuCtion oF thE wholE BoDy, AnD thEy ArE EssEntiAl to thE hEAlthy growth oF BoDy AnD minD、
thE thyroiD triEs to kEEp ConstAnt thE Amount oF CirCulAting thyroiD hormonE EntEring thE CElls oF thE BoDy. whEn ioDinE suppliEs ArE low, thE pituitAry glAnD, A smAll pEA-sizED glAnD At thE BAsE oF thE BrAin, sECrEtEs A thyroiD-stimulAting hormonE (tsh) thAt in turn rEgulAtEs thE powEr oF thE thyroiD to trAp ioDinE AnD inCrEAsE thE output oF thE thyroiD、iF thE thyroiD is ContinuAlly stimulAtED By tsh, thE CElls gEt lArgEr AnD EvEntuAlly thE wholE glAnD EnlArgEs with An inCrEAsE in thE numBEr oF its CElls. thE thyroiD mAy hAvE mAny tEmporAry CrisEs whErE ioDinE suppliEs ArE not ADEquAtE AnD whErE swElling in inDuCED unDE
ioDinE is A wEll-known ExAmplE oF A trACE minErAl whosE lACk in thE BoDy CrEAtEs An EAsily trEAtED DisEAsE. whEn thE thyroiD glAnD is not suppliED with suFFiCiEnt ioDinE to mAnuFACturE hormonEs, it EnlArgEs AnD Forms A goitEr or swElling oF thE nECk.At thE sAmE timE othEr symptoms, suCh As FAtiguE AnD sluggishnEss, wEight gAin, ColDnEss oF thE BoDy, AnD DEprEssion, mAy oCCur.
in thE unitED stAtEs goitEr wAs First notED in thE grEAt lAkEs rEgion, whErE in thE 1930s, As mAny As 40 pErCEnt oF thE pEoplE in somE ArEAs hAD goitEr, DuE mAinly to ioDinE-DEFiCiEnt soil. this sCArCity hAD BEEn CAusED By iCE AgE glACiErs mElting AnD wAshing thE ioDinE out oF thE soil.
to unDErstAnD how ioDinE DEFiCiEnCy lEADs to goitEr, it is nECEssAry to look At thE unDErlying physiology oF thE thyroiD glAnD、thE humAn thyroiD glAnD is thE only plACE in thE BoDy whErE ioDinE is storED, AnD it rEquirEs A DAily supply oF ABout 150 miCrogrAms oF ioDinE EntEring thE BoDy. whEn FooD or wAtEr is DigEstED, thE ioDinE it ContAins is EithEr tAkEn up By thE thyroiD or EliminAtED From thE BoDy through thE kiDnEys into thE urinE. whEn suppliEs ArE low, thE kiDnEys still EliminAtE ioDinE From thE BoDy so thE CApACity oF thE thyroiD to prEsErvE An ADEquAtE supply oF rAw mAtEriAl is thrEAtEnED、
thE thyroiD glAnD Consists oF thousAnDs oF BAlls oF CElls, CAllED thyroiD vEsiClEs, whiCh EnClosE A spACE FillED with A jEllylikE protEin CAllED thyrogloBulin. thEsE CElls hAvE An ExtrAorDinAry ABility to trAp ioDinE From thE BlooDstrEAm, AnD thE EFFiCiEnCy oF this trAp CAn BE inCrEAsED iF thE Amount oF ioDinE in thE BlooD CirCulAtion DECrEAsEs. onCE thE ioDinE is trAppED By thE thyroiD vEsiClEs it pAssEs into thE thyrogloBulin, whErE thE ACtuAl mAnuFACturE oF two kinDs oF thyroiD hormonEs tAkEs plACE. thE hormonEs ArE storED hErE until thEy trAvEl BACk through thE thyroiD vEsiClEs to EntEr thE BlooDstrEAm. thE thyroiD hormonEs ArE thEn tAkEn to EvEry pArt oF thE BoDy whErE thEy inFluEnCE thE rAtE At whiCh thE ChEmiCAl proCEssEs oF EvEry CEll proCEED、thEy hAvE A pErvAsivE EFFECt on thE Control oF oxygEn Consumption AnD hEAt proDuCtion oF thE wholE BoDy, AnD thEy ArE EssEntiAl to thE hEAlthy growth oF BoDy AnD minD、
thE thyroiD triEs to kEEp ConstAnt thE Amount oF CirCulAting thyroiD hormonE EntEring thE CElls oF thE BoDy. whEn ioDinE suppliEs ArE low, thE pituitAry glAnD, A smAll pEA-sizED glAnD At thE BAsE oF thE BrAin, sECrEtEs A thyroiD-stimulAting hormonE (tsh) thAt in turn rEgulAtEs thE powEr oF thE thyroiD to trAp ioDinE AnD inCrEAsE thE output oF thE thyroiD、iF thE thyroiD is ContinuAlly stimulAtED By tsh, thE CElls gEt lArgEr AnD EvEntuAlly thE wholE glAnD EnlArgEs with An inCrEAsE in thE numBEr oF its CElls. thE thyroiD mAy hAvE mAny tEmporAry CrisEs whErE ioDinE suppliEs ArE not ADEquAtE AnD whErE swElling in inDuCED unDE
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