醫(yī)學(xué)英語(yǔ)原文翻譯1至5單元

1.isthestudyofthefunctionsoflivingmatter.Itisconcernedwithhowanorganismperformsitsvariedactivities:howitfeeds,howitmoves,howitadaptstochangingcircumstances,howitspawnsnewgenerations.Thesubjectisvastandembracesthewholeoflife.Thesuccessofphysiologyinexplaininghoworganismsperformtheirdailytasksisbasedonthenotionthattheyareintricateandexquisitemachineswhoseoperationisgovernedbythelawsofphysicsandchemistry.Althoughsomeprocessesaresimilaracrossthewholespectrumofreplicationofthegeneticcodeforexample—manyarespecifictoparticulargroupsoforganisms.Forthisreasonitisnecessarytodividethesubjectintovariouspartssuchasbacterialphysiology,plantphysiology,andanimalphysiology.2.正如要了解一個(gè)動(dòng)物如何活動(dòng)，首先需要了解它的構(gòu)成，要充分了解一個(gè)生物體的生理學(xué)活動(dòng)就必須掌握全面的解剖學(xué)知識(shí)。一個(gè)生物體的各部分起著什么作用可通過(guò)實(shí)驗(yàn)觀察得知Tostudyhowananimalworksitisfirstnecessarytoknowhowitisbuilt.Afullappreciationofthephysiologyofanorganismmustthereforebebasedonasoundknowledgeofitsanatomy.Experimentscanthenbecarriedouttoestablishhowparticularpartsperformtheirfunctions.Althoughtherehavebeenmanyimportantphysiologicalinvestigationsonhumanvolunteers,theneedforprecisecontrolovertheexperimentalconditionshasmeantthatmuchofourpresentphysiologicalknowledgehasbeenderivedfromstudiesonotheranimalssuchasfrogs,rabbits,cats,anddogs.Whenitisclearthataspecificphysiologicalprocesshasacommonbasisinawidevarietyofanimalspecies,itisreasonabletoassumethatthesameprincipleswillapplytohumans.Theknowledgegainedfromthisapproachhasgivenusagreatinsightintohumanphysiologyandendoweduswithasolidfoundationfortheeffectivetreatmentofmanydiseases.Theorganizationofthebody3.機(jī)體的基本組成物質(zhì)是細(xì)胞，細(xì)胞結(jié)合在一大腦，脊髓，自主神經(jīng)和神經(jīng)中樞以及周?chē)|體神經(jīng)組成神經(jīng)系統(tǒng)等等。3.Thebuildingblocksofthebodyarethecells,whicharegroupedtogethertoformtissues.Theprincipaltypesoftissueareepithelial,connective,nervous,andmuscular,eachwithitsowncharacteristics.Manyconnectivetissueshaverelativelyfewcellsbuthaveanextensiveextracellularmatrix.Incontrast,smoothmuscleconsistsofdenselypackedlayersofmusclecellslinkedtogetherviaspecificcelljunctions.Organssuchasthebrain,theheart,thelungs,theintestines,andtheliverareformedbytheaggregationofdifferentkindsoftissues.Theorgansarethemselvespartsofdistinctphysiologicalsystems.Theheartandbloodvesselsformthecardiovascularsystem;thelungs,trachea,andbronchitogetherwiththechestwallanddiaphragmformtherespiratorysystem;theskeletonandskeletalmusclesformthemusculoskeletalsystem;thebrain,spinalcord,autonomicnervesandganglia,andperipheralsomaticnervesformthenervoussystem,andsoon.4.第一，細(xì)胞由一層薄膜也稱(chēng)細(xì)胞膜包被；第二，細(xì)胞能把大分子分解為小分子釋放能量供活(DNA)4.Cellsdifferwidelyinformandfunctionbuttheyallhavecertaincommoncharacteristics.First,theyareboundedbyalimitingmembrane,theplasmamembrane.Secondly,theyhavetheabilitytobreakdownlargemoleculestosmalleronestoliberateenergyfortheiractivities.Thirdly,atsomepointintheirlifehistory,theypossessanucleuswhichcontainsgeneticinformationintheformofdeoxyribonucleicacid(DNA).5.活體細(xì)胞不斷轉(zhuǎn)化物質(zhì)。細(xì)胞分解葡萄糖和脂肪，為自身生長(zhǎng)和修復(fù)所需的蛋白質(zhì)合成和運(yùn)動(dòng)等其它活動(dòng)提供能量。這些化學(xué)變化統(tǒng)稱(chēng)為新陳代謝。把大分子分解為小分子的過(guò)程稱(chēng)為分解代謝，小分子合成大分子的過(guò)程稱(chēng)為合成代謝。5.Livingcellscontinuallytransformmaterials.Theybreakdownglucoseandfatstoprovideenergyforotheractivitiessuchasmotilityandthesynthesisofproteinsforgrowthandrepair.Thesechemicalchangesarecollectivelycalledmetabolism.Thebreakdownoflargemoleculestosmalleronesiscalledcatabolismandthesynthesisoflargemoleculesfromsmalleronesanabolism.6.細(xì)胞在進(jìn)化過(guò)程中不斷分化進(jìn)行不同的功能活動(dòng)。有些細(xì)胞具有收縮能力（如肌細(xì)胞，有些可以傳導(dǎo)電信號(hào)（如神經(jīng)細(xì)胞。進(jìn)一步進(jìn)化的細(xì)胞能（如內(nèi)分泌細(xì)胞）6.Inthecourseofevolution,cellsbegantodifferentiatetoservedifferentfunctions.Somedevelopedtheabilitytocontract(musclecells),otherstoconductelectricalsignals(nervecells).Afurthergroupdevelopedtheabilitytosecretedifferentsubstancessuchashormonesorenzymes.Duringembryologicaldevelopment,thisprocessofdifferentiationisre-enactedasmanydifferenttypesofcellareformedfromthefertilizedegg.7.大多數(shù)組織包含有不同的細(xì)胞類(lèi)Mosttissuescontainamixtureofcelltypes.Forexample,bloodconsistsofredcells,whitecells,andplatelets.Redcellstransportoxygenaroundthebody.Thewhitecellsplayanimportantroleindefenseagainstinfectionandtheplateletsarevitalcomponentsintheprocessofbloodclotting.Thereareanumberofdifferenttypesofconnectivetissuebutallarecharacterizedbyhavingcellsdistributedwithinanextensivenoncellularmatrix.Nervetissuecontainsnervecellsandglialcells.8.大型多細(xì)胞動(dòng)物體的細(xì)胞不能產(chǎn)生氧氣和營(yíng)養(yǎng)物質(zhì)，需能之一，血液憑借心臟的泵血作用在血管內(nèi)流動(dòng)循環(huán)。Thecellsoflargemulticellularanimalscannotderivetheoxygenandnutrientstheyneeddirectlyfromtheexternalenvironment.Thesemustbetransportedtothecells.Thisisoneoftheprincipalfunctionsoftheblood,whichcirculateswithinbloodvesselsbyvirtueofthepumpingactionoftheheart.Theheart,bloodvessels,andassociatedtissuesformthecardiovascularsystem.Theheartconsistsoffourchambers,twoatriaandtwoventricles,whichformapairofpumpsarrangedsidebyside.Therightventriclepumpsdeoxygenatedbloodtothelungswhereitabsorbsoxygenfromtheair,whiletheleftventriclepumpsoxygenatedbloodreturningfromthelungstotherestofbodytosupplythetissues.Physiologistsareconcernedwithestablishingthefactorsresponsiblefortheheartbeat,howtheheartpumpsthebloodaroundthecirculation,andhowitisdistributedtoperfusethetissuesaccordingtotheirneeds.Fluidexchangedbetweenthebloodplasmaandthetissuespassesintothelymphaticsystem,whicheventuallydrainsbackintotheblood.（主要是糖類(lèi)和脂肪）氧氣頻率的因素是什么？Theenergyrequiredforperformingthevariousactivitiesofthebodyisultimatelyderivedfromrespiration.Thisprocessinvolvestheoxidationoffoodstuffstoreleasetheenergytheycontain.Theoxygenneededforthisprocessisabsorbedfromtheairinthelungsandcarriedtothetissuesbytheblood.Thecarbondioxideproducedbytherespiratoryactivityofthetissuesiscarriedtothelungsbythebloodinthepulmonaryarterywhereitisexcretedintheexpiredair.Thebasicquestionstobeansweredincludethefollowing:Howistheairmovedinandoutofthelungs?Howisthevolumeofairbreathedadjustedtomeettherequirementsofthebody?Whatlimitstherateofoxygenuptakeinthelungs?機(jī)體所需營(yíng)養(yǎng)物質(zhì)來(lái)源于飲食。食物經(jīng)口腔進(jìn)入體內(nèi)，在胃腸道內(nèi)經(jīng)酶將其分解成小分何消化的？食物如何被個(gè)體分解消化？個(gè)體營(yíng)養(yǎng)物質(zhì)如何吸收？食物如何在腸內(nèi)轉(zhuǎn)運(yùn)的？Thenutrientsneededbythebodyarederivedfromthediet.Foodistakeninbythemouthandbrokendownintoitscomponentpartsbyenzymesinthegastrointestinaltract.Thedigestiveproductsarethenabsorbedintothebloodacrossthewalloftheintestineandpasstotheliverviatheportalvein.Thelivermakesnutrientsavailabletothetissuesbothfortheirgrowthandrepairandfortheproductionofenergy.Inthecaseofthedigestivesystem,keyphysiologicalquestionsare:Howisfoodingested?Howisitbrokendownanddigested?Howaretheindividualnutrientsabsorbed?Howisthefoodmovedthroughthegut?Howaretheindigestibleremainseliminatedfromthebody?腎臟主要功能是控制細(xì)胞外液體的形成。在這一過(guò)程中，腎臟也會(huì)把不可揮發(fā)的廢物排應(yīng)對(duì)像脫水這樣的應(yīng)激反應(yīng)？以及尿液可以存儲(chǔ)和排出體外的機(jī)制是什么？12.Thechieffunctionofthekidneysistocontrolthecompositionoftheextracellularfluid.Inthecourseofthisprocess,theyalsoeliminatenon-volatilewasteproductsfromtheblood.Toperformthesefunctions,thekidneysproduceurineofvariablecompositionwhichistemporarilystoredinthebladderbeforevoiding.Thekeyphysiologicalquestionsinthiscaseare:howdothekidneysregulatethecompositionoftheblood?Howdotheyeliminatetoxicwaste?Howdotheyrespondtostressessuchasdehydration?Whatmechanismsallowthestorageandeliminationoftheurine?Thereproductivesystem13.生殖是活生物體的一個(gè)基本特征。生殖腺產(chǎn)生專(zhuān)門(mén)的性細(xì)胞，被稱(chēng)為配子。性生殖的核心是雌雄配子即精子和卵子的產(chǎn)生和融合，因此兩個(gè)獨(dú)立個(gè)體的基因特征融合而產(chǎn)生一個(gè)基因上與雙親不同的后代。13.Reproductionisoneofthefundamentalcharacteristicsoflivingorganisms.Thegonadsproducespecializedsexcellsknownasgametes.Atthecoreofsexualreproductionisthecreationandfusionofthemaleandfemalegametes,thespermandova(eggs),withtheresultthatthegeneticcharacteristicsoftwoseparateindividualsaremixedtoproduceoffspringthatdiffergeneticallyfromtheirparents.14.這一系統(tǒng)由骨、骨骼肌、關(guān)節(jié)和它們的相關(guān)組織組成。其主要功能是提供運(yùn)動(dòng)需要，維分泌系統(tǒng)和神經(jīng)系統(tǒng)14.Thisconsistsofthebonesoftheskeleton,skeletalmuscles,joints,andtheirassociatedtissues.Itsprimaryfunctionistoprovideameansofmovement,whichisrequiredforlocomotion,forthemaintenanceofposture,andforbreathing.ItalsoprovidesphysicalsupportfortheinternalorgansHerethemechanismofmusclecontractionisacentralissue.Theendocrineandnervoussystems15.不同器官系統(tǒng)的活動(dòng)需要協(xié)作和調(diào)節(jié)，以便共同作用滿足機(jī)體需要。人體有兩大調(diào)節(jié)系15.Theactivitiesofthedifferentorgansystemsneedtobecoordinatedandregulatedsothattheyacttogethertomeettheneedsofthebody.Twocoordinatingsystemshaveevolved:thenervoussystemandtheendocrinesystem.Thenervoussystemuseselectricalsignalstotransmitinformationveryrapidlytospecificcells.Thusthenervespasselectricalsignalstotheskeletalmusclestocontroltheircontraction.Theendocrinesystemsecreteschemicalagents,hormones,whichtravelinthebloodstreamtothecellsuponwhichtheyexertaregulatoryeffect.Hormonesplayamajorroleintheregulationofmanydifferentorgansandareparticularlyimportantintheregulationofthemenstrualcycleandotheraspectsofreproduction.16.免疫系統(tǒng)通過(guò)殺死入侵的有機(jī)體，清除致病或損傷細(xì)胞為機(jī)體提供防御功能。Theimmunesystemprovidesthedefensesagainstinfectionbothbykillinginvadingorganismsandbyeliminatingdiseasedordamagedcells.Althoughitishelpfultostudyhoweachorganperformsitsfunctions,itisessentialtorecognizethattheactivityofthebodyasawholeisdependentontheintricateinteractionsbetweenthevariousorgansystems.Ifonepartfails,theconsequencesarefoundinotherorgansystemsthroughoutthewholebody.Forexample,ifthekidneysbegintofail,theregulationoftheinternalenvironmentisimpairedwhichinturnleadstodisordersoffunctionelsewhere.各種復(fù)雜機(jī)制共同作用調(diào)節(jié)細(xì)胞外液的形成，不同個(gè)體細(xì)胞有自身機(jī)制調(diào)節(jié)內(nèi)在組成成被稱(chēng)為穩(wěn)態(tài)，它是機(jī)體能夠正常發(fā)揮作用所必須的。18.Complexmechanismsareatworktoregulatethecompositionoftheextracellularfluidandindividualcellshavetheirownmechanismsforregulatingtheirinternalcomposition.Theregulatorymechanismsstabilizetheinternalenvironmentdespitevariationsinboththeexternalworldandtheactivityoftheanimal.Theprocessofstabilizationoftheinternalenvironmentiscalledhomeostasisandisessentialifthecellsofthebodyaretofunctionnormally.例如，心臟的跳動(dòng)依賴(lài)于心肌細(xì)胞有節(jié)律的收縮。這一活動(dòng)依賴(lài)于電信號(hào)，而電信號(hào)反子的濃度就必須控制在一定范圍內(nèi)。Totakeoneexample,thebeatingoftheheartdependsontherhythmicalcontractionsofcardiacmusclecells.Thisactivitydependsonelectricalsignalswhich,inturn,dependontheconcentrationofsodiumandpotassiumionsintheextracellularandintracellularfluids.Ifthereisanexcessofpotassiumintheextracellularfluid,thecardiacmusclecellsbecometooexcitableandmaycontractatinappropriatetimesratherthaninacoordinatedmanner.Consequently,theconcentrationofpotassiumintheextracellularfluidmustbekeptwithinanarrowrangeiftheheartistobeatnormally.1千克食物，2-330千克食物，60-90升液體。然而，一般來(lái)說(shuō)，機(jī)體體重是基本不變的。這類(lèi)個(gè)體可以說(shuō)處于Inthecourseofaday,anadultconsumesapproximately1kgoffoodanddrinkslitersoffluid.Inamonth,thisisequivalenttoaround30kgoffoodandlitersoffluid.Yet,ingeneral,bodyweightremainsremarkablyconstant.Suchindividualsaresaidtobeinbalance;theintakeoffoodanddrinkmatchestheamountsusedtogenerateenergyfornormalbodilyactivitiesplusthelossesinurineandfeces.Insomecircumstances,suchasstarvation,intakedoesnotmatchtheneedsofthebodyandmuscletissueisbrokendowntoprovideglucoseforthegenerationofenergy.Here,theintakeofproteinislessthantherateofbreakdownandtheindividualissaidtohaveanegativenitrogenbalance.Equally,ifthebodytissuesarebeingbuiltup,asisthecaseforgrowingchildren,pregnantwomenandathletesintheearlystagesoftraining,thedailyintakeofproteinisgreaterthanthenormalbodyturnoverandtheindividualisinpositivenitrogenbalance.平衡的概念可以應(yīng)用到機(jī)體的任何構(gòu)成成分上，包括水和鹽，而且平衡在機(jī)體調(diào)節(jié)其自4-5mmol.l–1.進(jìn)食后不久，血糖含量超過(guò)這一范圍，刺激胰腺分泌在胰島素分泌期間，葡萄糖像肝糖原或脂肪一樣被儲(chǔ)存。Thisconceptofbalancecanbeappliedtoanyofthebodyconstituentsincludingwaterandsaltandisimportantinconsideringhowthebodyregulatesitsowncomposition.Intakemustmatchrequirementsandanyexcessmustbeexcretedforbalancetobemaintained.Additionally,foreachchemicalconstituentofthebodythereisadesirableconcentrationrange,whichthecontrolmechanismsareadaptedtomaintain.Forexample,theconcentrationofglucoseintheplasmaisaboutmmol.l–1betweenmeals.Shortlyafterameal,plasmaglucoserisesabovethislevelandthisstimulatesthesecretionofthehormoneinsulinbythepancreas,whichactstobringtheconcentrationdown.Astheconcentrationofglucosefalls,sodoesthesecretionofinsulin.Ineachcase,thechangesinthecirculatinglevelofinsulinacttomaintaintheplasmaglucoseatanappropriatelevel.Thistypeofregulationisknownasnegativefeedback.Duringtheperiodofinsulinsecretion,theglucoseisbeingstoredaseitherglycogenorfat.負(fù)反饋環(huán)是在機(jī)體出現(xiàn)紊亂時(shí)，將一些變量控制在限定范圍內(nèi)的一個(gè)控制系統(tǒng)。雖然上加熱器關(guān)閉。anegativefeedbackloopisacontrolsystemthatactstomaintainthelevelofsomevariablewithinagivenrangefollowingadisturbance.Althoughtheexamplegivenabovereferstoplasmaglucose,thebasicprinciplecanbeappliedtootherphysiologicalvariablessuchasbodytemperature,bloodpressure,andtheosmolalityoftheplasma.anegativefeedbacklooprequiresasensorofsomekindthatrespondstothevariableinquestionbutnottootherphysiologicalbariables,thusanosmoreceptorshouldrespindtochangesinosmolalityofthebodyfluidsbutnottochangesinbodytemperatureorbloodpressure.theinformationfromthesensormustbecomparedinsomewaywiththedesiredlevelbysomeformofcomparator.ifthetwodonotmatch,anerrorsignalistransmittedtoaneffector,asystemthatcanacttorestorethevariabletoitsdesiredlevel.thesefeaturesofnegativefeedbackcanbeappreciatedbyexaminingasimpleheatingsystem.thecontrolledvariableisroomtemperature,whichissensedbyathermostat.theeffectorisaheaterofsomekind.whentheroomtemperaturefallsbelowthesetpoint,thetemperaturedifferenceisdetectedbythethermostatwhichswitchesontheheater.thisheatstheroomuntilthetemperaturereachesthepersetlevelwhereupontheheaterisswitchedoff.23.總而言之，機(jī)體實(shí)際上是由100萬(wàn)億細(xì)胞有序組成了不同的功能結(jié)構(gòu)，其中一些被稱(chēng)為致疾病的發(fā)生。23.Tosumarize,thebodyisactuallyasocialorderofabout100trillioncellsorganizedintodifferentfunctionalstructures,someofwhicharecalledorgans.eachfunctionalstructuresitssharetothemaintenanceofhomeostaticconditionsintheextracellularfluid,whichiscalledtheinternalenvironment.aslongasnormalconditionsaremaintainedinthisinternalenvironment,thecellsofthebodycontinuetoliveandfunctionproperly.Eachcellbenefitsfromhomeostasis,andinturn,eachcellcontributesitssharetowardthemaintenanceofhomeostasis.Thisreciprocalinterplayprovidescontinuousautomaticityofthebodyuntiloneormorefunctionalsystemslosetheirabilitytocontributetheirshareoffunction.Whenthishappens,allthecellsofthebodysuffer.Extremedysfunctionleadstodeath;moderatedysfunctionleadstosickness.,是兩個(gè)心房的同時(shí)收縮Thecardiaccycleisthesequenceofeventsinoneheartbeat.Initssimplestform,thecardiaccycleisthesimultaneouscontractionofthetwoatria,followedafractionofasecondlaterbythesimultaneouscontractionofthetwoventricles.Thereis,however,asignificantdifferencebetweenthemovementofbloodfromtheatriatotheventricles,andthemovementofbloodfromtheventriclestothearteries.血液的壓力會(huì)打開(kāi)左右房室瓣。兩個(gè)心房里三分之二的血液被動(dòng)地流入到心室中;然后，心房收縮將剩余血液泵入心室。Bloodisconstantlyflowingfromtheveinsintobothatria.Asmorebloodaccumulates,itspressureforcesopentherightandleftAVvalves.Twothirdsoftheatrialbloodflowspassivelyintotheventricles;theatriathencontracttopumptheremainingbloodintotheventricles.心房收縮后舒張，心室開(kāi)始收縮。心室的收縮使血液施壓于左右房室瓣的皮瓣并使其閉合同時(shí)血液繼續(xù)流入心房，循環(huán)重新開(kāi)始。Followingtheircontraction,theatriarelaxandtheventriclesbegintocontract.VentricularcontractionforcesbloodagainsttheflapsoftherightandleftAVvalvesandclosesthem;theforceofbloodalsoopenstheaorticandpulmonarysemilunarvalves.Astheventriclescontinuetocontract,theypumpbloodintothearteries.Thebloodthatentersthearteriesmustallbepumped.Theventriclesthenrelax,andatthesametimebloodcontinuestoflowintotheatria,andthecyclewillbeginagain.這里一個(gè)重要的不同點(diǎn)就是大部分血液是被動(dòng)地從心房流入心室,但是所有注入動(dòng)脈的血液均由心室主動(dòng)射出。因此,對(duì)生存來(lái)說(shuō)，心室的正常工作遠(yuǎn)比心房的工作重要的多。Theimportantdistinctionhereisthatmostbloodflowspassivelyfromatriatoventricles,butallbloodtothearteriesisactivelypumpedbytheventricles.Forthisreason,theproperfunctioningoftheventriclesismuchmorecrucialtosurvivalthanisatrialfunctioning.收縮的另一個(gè)術(shù)語(yǔ)是心臟收縮。松弛的術(shù)語(yǔ)是心臟舒張。您可能比較熟悉這些術(shù)語(yǔ)，因?yàn)?張。Thereisanothertermforcontraction,andthatissystole.Thetermforrelaxationisdiastole.Youareprobablyfamiliarwiththesetermsastheyrelatetobloodpressurereadings.Ifweapplythemtothecardiaccycle,wecansaythatatrialsystoleisfollowedbyventricularsystole.Anotherwaytoputitisthatwhentheatriaareinsystole,theventriclesareindiastole,andwhentheventriclesareinsystole,theatriaareindiastole.列精確的活動(dòng)組成，這些活動(dòng)使血液從靜脈流過(guò)心臟最后再注入動(dòng)脈。Youmaybeasking:allthisinoneheartbeat?Theanswerisyes.Thecardiaccycleisthisprecisesequenceofeventsthatkeepsbloodmovingfromtheveins,throughtheheartandintothearteries.7.心臟血液循環(huán)同時(shí)產(chǎn)生心:每一次心跳會(huì)有兩個(gè)聲音用聽(tīng)診器可以聽(tīng)見(jiàn)。第一,最大也最長(zhǎng),是由心室收縮閉合房室瓣而引起的。第二聲是由動(dòng)脈和肺的半月瓣的閉合造成的。如果任一瓣膜閉合不全,就會(huì)聽(tīng)見(jiàn)另外一個(gè)聲音，稱(chēng)為―心臟雜音‖。Thecardiaccyclealsocreatestheheartsounds:eachheartbeatproducestwosounds,whichcanbeheardwithastethoscope.Thefirstsound,theloudestandlongest,iscausedbyventricularsystoleclosingtheAVvalves.Thesecondsoundiscausedbytheclosureoftheaorticandpulmonarysemi-lunarvalves.Ifanyofthevalvesdonotcloseproperly,anextrasoundcalledaheartmurmurmaybeheard. 心臟的傳導(dǎo)途徑非由神經(jīng)脈沖引起。心臟自行跳動(dòng)，腦電脈沖沿一確定路徑穿過(guò)心肌層。Thecardiaccycleisasequenceofmechanicaleventsthatisregulatedbytheelectricalactivityofthemyocardium.Cardiacmusclecellshavetheabilitytocontractspontaneously,thatis,nerveimpulsesarenotrequiredtocausecontraction.Theheartgeneratesitsownbeat,andtheelectricalimpulsesfollowaveryspecificroutethroughoutthemyocardium.心臟的自然起搏器是竇房結(jié)，它是位于右心房壁上的特化心肌細(xì)胞群。竇房結(jié)被認(rèn)為是特化的是因?yàn)樗凶羁斓氖湛s速度。Thenaturalpacemakeroftheheartisthesinoatrial(SA)node,aspecializedgroupofcardiacmusclecellslocatedinthewalloftherightatrium.TheSAnodeisconsideredspecializedbecauseithasthemostrapidrateofcontraction,thatis,itdepolarizesmorerapidlythananyotherpartofthemyocardium.收縮脈沖從竇房結(jié)運(yùn)行到房室結(jié)，房室結(jié)位于心房間隔膜區(qū)下部。從竇房結(jié)和房室結(jié)到心房心肌層的其余部分的脈沖傳導(dǎo)可引起心房收縮。FromtheSAnode,impulsesforcontractiontraveltotheatrioventricularnode,locatedinthelowerinteratrialseptum.ThetransmissionofimpulsesfromtheSAnodeandAVnodetotherestoftheatrialmyocardiumbringsaboutatrialsystole.它接收來(lái)自房室結(jié)的脈沖，并傳給左右神經(jīng)束支。脈沖從神經(jīng)束支開(kāi)始，沿著普肯野纖維到達(dá)心室心肌層的其他部分,并引起心室收縮。心電圖可以顯示心房和心室的電子活動(dòng)。WithintheupperinterventricularseptumistheBundleofHis(AVbundle),whichreceivesimpulsesfromtheAVnodeandtransmitsthemtotherightandleftbundlebranches.Fromthebundlebranches,impulsestravelalongPurkinjefiberstotherestoftheventricularmyocardium,andbringaboutventricularsystole.Theelectricalactivityoftheatriaandventriclesisdepictedbyanelectrocardiogram(ECG)但速度較慢5060下1540下)是由心房到心室的脈沖傳導(dǎo)被阻礙而引發(fā)IftheSAnodedoesnotfunctionproperly,theAVnodewillinitiatetheheartbeat,butataslowerrate(50to60beatsperminute).TheBundleofHisisalsocapableofgeneratingthebeatoftheventricles,butatamuchslowerrate(15to40beatsperminute).Thismayoccurincertain13.心率失常是不規(guī)則的心跳它們的影響范圍小到對(duì)人體無(wú)害大到威而且可能是因?yàn)檫^(guò)多攝入了完全無(wú)法泵出血液的心室悸實(shí)Arrhythmiasareirregularheartbeats;theireffectsrangefromharmlesstolife-threatening.Nearlyeveryoneexperiencesheartpalpitationsfromtimetotime.Theseareusuallynotserious,andmaybetheresultoftoomuchcaffeine,nicotine,oralcohol.Muchmoreseriousisventricularfibrillation,averyrapidanduncoordinatedventricularbeatthatistotallyineffectiveforpumpingblood.心率6080下，是竇房結(jié)去極化的速度。一100120140物得到啟示：老鼠的心率在每分鐘200次左右，而大象的心率在每分鐘30次左右。Ahealthyadulthasarestingheartrate(pulse)of60to80beatsperminute,whichistherateofdepolarizationoftheSAnode.Achildnrmalheartratemaybeashighas100beatsperminute,thatofaninfantashighas120,andthatofanear-termfetusashighas140beatsperminute.Thesehigherratesarenotrelatedtoage,butrathertosize:thesmallertheindividual,thehigherthemetabolicrateandthefastertheheartrate.Parallelsmaybefoundamonganimalsofdifferentsizes;theheartrateofamouseisabout200beatsperminute,andthatofanelephantabout30beatsperminute.讓我們回到成人心率這個(gè)問(wèn)題上來(lái)，設(shè)定一個(gè)人擁有良好的健康狀況。正如你所知，一個(gè)身體狀態(tài)良好的運(yùn)動(dòng)員的心率較低。那些籃球運(yùn)動(dòng)員的脈搏在每分鐘50次左右，馬拉松3540持續(xù)的運(yùn)動(dòng)使得心臟泵血更加有力。心 輸 出 量Letusreturntotheadultheartrate,andconsiderthepersonwhoisinexcellentphysicalcondition.Asyoumayknow,well-conditionedathleteshavelowrestingpulserates.Thoseofbasketballplayersareoftenaround50beatsperminute,andthepulseofamarathonrunneroftenrangesfrom35to40beatsperminute.Tounderstandwhythisisso,rememberthattheheartisamuscle.Whenourskeletalmusclesareexercised,theybecomestrongerandmoreefficient.Thesameistruefortheheart;consistentexercisemakesitamoreefficientpump,asyouwillseeinthenextdiscussion.Cardiacoutputistheamountofbloodpumpedbyaventricleinoneminute.Acertainlevelofcardiacoutputisneededatalltimestotransportoxygentotissuesandtoremovewasteproducts.Duringexercise,cardiacoutputmustincreasetomeetthebody’sneedformoreoxygen.Wewillreturntoexerciseafterfirstconsideringrestingcardiacoutput.為了計(jì)算心輸出量，我們必須知道心率和每次心跳所泵出的血液量。心臟供血量這一術(shù)60毫升。下面這個(gè)簡(jiǎn)單的公式能使我們很容易計(jì)算出心輸出Inordertocalculatecardiacoutput,wemustknowthepulserateandhowmuchbloodispumpedperbeat.Strokevolumeisthetermfortheamountofbloodpumpedbyaventricleperbeat;anaveragerestingstrokevolumeis60to80mlperbeat.Asimpleformulathenenablesustodeterminecardiacoutput:Cardiacoutput＝Strokevolume×pulse(heartrate)我們假定人安靜時(shí)的心室跳動(dòng)一次的供血量為7070量＝70ml70bpm（每分鐘脈搏次數(shù)）＝4900ml/m5L)Letusputintothisformulaanaveragerestingstrokevolume,70ml,andanaveragerestingpulse,70beatsperminute(bpm): Cardiacoutput＝70ml×70bpm Cardiactput＝4,900mlperminute (approximately5liters)當(dāng)然心輸出量的多少會(huì)隨著人體型的大小而變，但人在靜息狀態(tài)下的心輸出量是每分56升。Naturally,cardiacoutputvarieswiththesizeoftheperson,buttheaveragerestingcardiacoutputis5to6litersperminute.,550輸出量＝5,000/50＝100每搏量Ifwenowreconsidertheathlete,youwillbeabletoseepreciselywhytheathletehasalowrestingpulse.Inourformula,wewilluseanaveragerestingcardiacoutput(5liters)andanathlete’spulserate(50):CardiacOutput＝Strokevolume×pulse 5,000/50＝Strokevolume 100mlStrokevolume我們注意到靜息狀態(tài)下運(yùn)動(dòng)員的心臟供血量明顯高于常人。運(yùn)動(dòng)員的強(qiáng)有力的心臟每次跳動(dòng)能為身體提供更多血液。因此，靜息狀態(tài)下他們保持一個(gè)較低的心率 。 Noticethattheathlete srestingstrokevolumeissignificantlyhigherthantheaverage.Theathlete’smoreefficientheartpumpsmorebloodwitheachbeat,andsocanmaintainanormalrestingcardiacoutputwithfewerbeats.現(xiàn)在我們?cè)倏紤]一下心臟對(duì)運(yùn)動(dòng)作何反映。人在運(yùn)動(dòng)的過(guò)程中心率會(huì)加快，心輸出量也心臟供血量的計(jì)算公式如下：kindsofheartdiseaseinwhichtransmissionofimpulsesfromtheatriatotheventriclesisblocked.心輸出量＝每搏量×心率 心輸出量＝100ml×100bpm心輸出量＝10,000ml(10liters)Nowletusseehowtheheartrespondstoexercise.Heartrate(pulse)increasesduringexercise,andsodoesstrokevolume.TheincreaseinstrokevolumeistheresultofStarling’sLawoftheHeart,whichstatesthatthemorethecardiacmusclefibersarestretched,themoreforcefullytheycontract.Duringexercise,morebloodreturnstotheheart;thisiscalledvenousreturn.Increasedvenousreturnstretchesthemyocardiumoftheventricles,whichcontractmoreforcefullyandpumpmoreblood,therebyincreasingstrokevolume.Therefore,duringexercise,ourformulamightbethefollowing: Cardiacoutput ＝ Stroke×pulse Cardiacoutput＝100ml×100bpm Cardiacoutput＝10,000ml(10liters)一個(gè)健康年輕人每分鐘的心輸出量可以增加到他安靜時(shí)的４倍Thisexercisecardiacoutputistwicetherestingcardiacoutputwefirstcalculated,whichshouldnotbeconsideredunusual.Thecardiacoutputofahealthyyoungpersonmayincreaseuptofourtimestherestinglevelduringstrenuousexercise.Thisexercisecardiacoutputistwicetherestingcardiacoutputwefirstcalculated,whichshouldnotbeconsideredunusual.Thecardiacoutputofahealthyyoungpersonmayincreaseuptofourtimestherestinglevelduringstrenuousexercise.心率的調(diào)節(jié)雖然心臟自行跳動(dòng)并保持其跳動(dòng)，但心臟收縮的頻率可根據(jù)情況的不同而發(fā)生變化。神經(jīng)系統(tǒng)可以調(diào)節(jié)心臟收縮的力度并控制心率的必要變Althoughtheheartgeneratesandmaintainsitsownbeat,therateofcontractioncanbechangedtoadapttodifferentsituations.Thenervoussystemcananddoesbringaboutnecessarychangesinheartrateaswellasinforceofcontraction.腦髓質(zhì)有兩個(gè)心血管控制中心：加速中樞和抑制中樞。兩中樞通過(guò)自主神經(jīng)向心臟傳送過(guò)迷走神經(jīng)傳輸?shù)叫呐K，降低心臟跳動(dòng)的速率。Themedullaofthebraincontainsthetwocardiaccenters,theacceleratorcenterandtheinhibitorycenter.Thesecenterssendimpulsestotheheartalongautonomicnerves.Theautonomicnervoussystemhastwodivisions:sympatheticandparasympathetic.Sympatheticimpulsesfromtheacceleratorcenteralongsympatheticnervesincreaseheartrateandforceofcontraction.Parasympatheticimpulsesfromtheinhibitorycenteralongthevagusnervesdecreasetheheartrate.我們下一個(gè)問(wèn)題是腦髓質(zhì)接受了什么信息才引起這些變化呢？既然心臟泵出血液，維持血液中含氧量的變化就會(huì)刺激心率產(chǎn)生相應(yīng)的變化。Ournextquestionmightbe:whatinformationisreceivedbythemedullatoinitiatechanges?Sincetheheartpumpsblood,itisessentialtomaintainnormalbloodpressure.Bloodcontainsoxygen,whichalltissuesmustreceivecontinuously.Therefore,changesinbloodpressureandoxygenlevelofthebloodarestimuliforchangesinheartrate.心輸出量＝每搏量×心率 心輸出量＝100ml×100bpm心輸出量＝10,000ml(10liters)Nowletusseehowtheheartrespondstoexercise.Heartrate(pulse)increasesduringexercise,andsodoesstrokevolume.TheincreaseinstrokevolumeistheresultofStarling’sLawoftheHeart,whichstatesthatthemorethecardiacmusclefibersarestretched,themoreforcefullytheycontract.Duringexercise,morebloodreturnstotheheart;thisiscalledvenousreturn.Increasedvenousreturnstretchesthemyocardiumoftheventricles,whichcontractmoreforcefullyandpumpmoreblood,therebyincreasingstrokevolume.Therefore,duringexercise,ourformulamightbethefollowing:Cardiacoutput＝Strokevolume×pulseCardiacoutput＝100ml×100bpmCardiacoutput＝10,000ml(10liters)一個(gè)健康年輕人每分鐘的心輸出量可以增加到他安靜時(shí)的４倍Thisexercisecardiacoutputistwicetherestingcardiacoutputwefirstcalculated,whichshouldnotbeconsideredunusual.Thecardiacoutputofahealthyyoungpersonmayincreaseuptofourtimestherestinglevelduringstrenuousexercise.Thisexercisecardiacoutputistwicetherestingcardiacoutputwefirstcalculated,whichshouldnotbeconsideredunusual.Thecardiacoutputofahealthyyoungpersonmayincreaseuptofourtimestherestinglevelduringstrenuousexercise.心率的調(diào)節(jié)雖然心臟自行跳動(dòng)并保持其跳動(dòng)，但心臟收縮的頻率可根據(jù)情況的不同而發(fā)生變化。神經(jīng)系統(tǒng)可以調(diào)節(jié)心臟收縮的力度并控制心率的必要變Althoughtheheartgeneratesandmaintainsitsownbeat,therateofcontractioncanbechangedtoadapttodifferentsituations.Thenervoussystemcananddoesbringaboutnecessarychangesinheartrateaswellasinforceofcontraction.腦髓質(zhì)有兩個(gè)心血管控制中心：加速中樞和抑制中樞。兩中樞通過(guò)自主神經(jīng)向心臟傳送過(guò)迷走神經(jīng)傳輸?shù)叫呐K，降低心臟跳動(dòng)的速率。Themedullaofthebraincontainsthetwocardiaccenters,theacceleratorcenterandtheinhibitorycenter.Thesecenterssendimpulsestotheheartalongautonomicnerves.Theautonomicnervoussystemhastwodivisions:sympatheticandparasympathetic.Sympatheticimpulsesfromtheacceleratorcenteralongsympatheticnervesincreaseheartrateandforceofcontraction.Parasympatheticimpulsesfromtheinhibitorycenteralongthevagusnervesdecreasetheheartrate.我們下一個(gè)問(wèn)題是腦髓質(zhì)接受了什么信息才引起這些變化呢？既然心臟泵出血液，維持血液中含氧量的變化就會(huì)刺激心率產(chǎn)生相應(yīng)化。Ournextquestionmightbe:whatinformationisreceivedbythemedullatoinitiatechanges?Sincetheheartpumpsblood,itisessentialtomaintainnormalbloodpressure.Bloodcontainsoxygen,whichalltissuesmustreceivecontinuously.Therefore,changesinbloodpressureandoxygenlevelofthebloodarestimuliforchangesinheartrate.壓力感受器和化學(xué)受體位于頸動(dòng)脈和主動(dòng)脈弓。位于頸動(dòng)脈竇和主動(dòng)脈竇的壓力感受器些事實(shí)集中在一個(gè)特例中，我們就可以看出心臟調(diào)節(jié)是一種反射。Pressoreceptorsandchemoreceptorsarelocatedinthecarotidarteriesandaorticarch.orsinthecarotidsinusesandaorticsinusdetectchangesinbloodpressure.Chemoreceptorsinthecarotidbodiesandaorticbodydetectchangesintheoxygencontentoftheblood.Thesensorynervesforthecarotidreceptorsaretheglossopharyngealnerves;thesensorynervesforaorticarchreceptorsarethevagusnerves.Ifwenowputallthesefactstogetherinaspecificexample,youwillseethattheregulationofheartrateisareflex.一個(gè)處于臥位的人突然變?yōu)檎疚?，或許會(huì)感到一陣稍微的頭暈，這是因?yàn)槟X部血壓突降這些副交感神經(jīng)脈沖減緩心率至正常休息頻率。Apersonwhostandsupsuddenlyfromalyingpositionmayfeellight-headedordizzyforafewmoments,becausebloodpressuretothebrainhasdecreasedabruptly.Thedropinbloodpressureisdetectedbypressoreceptorsinthecarotidnoticethattheyare“ontheway”tothebrain,averystrategiclocation.Impulsesgeneratedbythepressoreceptorstrav