1.isthestudyofthefunctionsoflivingmatter.Itisconcernedwithhowanorganismperformsitsvariedactivities:howitfeeds,howitmoves,howitadaptstochangingcircumstances,howitspawnsnewgenerations.Thesubjectisvastandembracesthewholeoflife.Thesuccessofphysiologyinexplaininghoworganismsperformtheirdailytasksisbasedonthenotionthattheyareintricateandexquisitemachineswhoseoperationisgovernedbythelawsofphysicsandchemistry.Althoughsomeprocessesaresimilaracrossthewholespectrumofreplicationofthegeneticcodeforexample—manyarespecifictoparticulargroupsoforganisms.Forthisreasonitisnecessarytodividethesubjectintovariouspartssuchasbacterialphysiology,plantphysiology,andanimalphysiology.2.正如要了解一個動物如何活動，首先需要了解它的構成，要充分了解一個生物體的生理學活動就必須掌握全面的解剖學知識。一個生物體的各部分起著什么作用可通過實驗觀察得知Tostudyhowananimalworksitisfirstnecessarytoknowhowitisbuilt.Afullappreciationofthephysiologyofanorganismmustthereforebebasedonasoundknowledgeofitsanatomy.Experimentscanthenbecarriedouttoestablishhowparticularpartsperformtheirfunctions.Althoughtherehavebeenmanyimportantphysiologicalinvestigationsonhumanvolunteers,theneedforprecisecontrolovertheexperimentalconditionshasmeantthatmuchofourpresentphysiologicalknowledgehasbeenderivedfromstudiesonotheranimalssuchasfrogs,rabbits,cats,anddogs.Whenitisclearthataspecificphysiologicalprocesshasacommonbasisinawidevarietyofanimalspecies,itisreasonabletoassumethatthesameprincipleswillapplytohumans.Theknowledgegainedfromthisapproachhasgivenusagreatinsightintohumanphysiologyandendoweduswithasolidfoundationfortheeffectivetreatmentofmanydiseases.Theorganizationofthebody3.機體的基本組成物質是細胞，細胞結合在一大腦，脊髓，自主神經和神經中樞以及周圍軀體神經組成神經系統等等。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，細胞由一層薄膜也稱細胞膜包被；第二，細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.活體細胞不斷轉化物質。細胞分解葡萄糖和脂肪，為自身生長和修復所需的蛋白質合成和運動等其它活動提供能量。這些化學變化統稱為新陳代謝。把大分子分解為小分子的過程稱為分解代謝，小分子合成大分子的過程稱為合成代謝。5.Livingcellscontinuallytransformmaterials.Theybreakdownglucoseandfatstoprovideenergyforotheractivitiessuchasmotilityandthesynthesisofproteinsforgrowthandrepair.Thesechemicalchangesarecollectivelycalledmetabolism.Thebreakdownoflargemoleculestosmalleronesiscalledcatabolismandthesynthesisoflargemoleculesfromsmalleronesanabolism.6.細胞在進化過程中不斷分化進行不同的功能活動。有些細胞具有收縮能力（如肌細胞，有些可以傳導電信號（如神經細胞。進一步進化的細胞能（如內分泌細胞）6.Inthecourseofevolution,cellsbegantodifferentiatetoservedifferentfunctions.Somedevelopedtheabilitytocontract(musclecells),otherstoconductelectricalsignals(nervecells).Afurthergroupdevelopedtheabilitytosecretedifferentsubstancessuchashormonesorenzymes.Duringembryologicaldevelopment,thisprocessofdifferentiationisre-enactedasmanydifferenttypesofcellareformedfromthefertilizedegg.7.大多數組織包含有不同的細胞類Mosttissuescontainamixtureofcelltypes.Forexample,bloodconsistsofredcells,whitecells,andplatelets.Redcellstransportoxygenaroundthebody.Thewhitecellsplayanimportantroleindefenseagainstinfectionandtheplateletsarevitalcomponentsintheprocessofbloodclotting.Thereareanumberofdifferenttypesofconnectivetissuebutallarecharacterizedbyhavingcellsdistributedwithinanextensivenoncellularmatrix.Nervetissuecontainsnervecellsandglialcells.8.大型多細胞動物體的細胞不能產生氧氣和營養物質，需能之一，血液憑借心臟的泵血作用在血管內流動循環。Thecellsoflargemulticellularanimalscannotderivetheoxygenandnutrientstheyneeddirectlyfromtheexternalenvironment.Thesemustbetransportedtothecells.Thisisoneoftheprincipalfunctionsoftheblood,whichcirculateswithinbloodvesselsbyvirtueofthepumpingactionoftheheart.Theheart,bloodvessels,andassociatedtissuesformthecardiovascularsystem.Theheartconsistsoffourchambers,twoatriaandtwoventricles,whichformapairofpumpsarrangedsidebyside.Therightventriclepumpsdeoxygenatedbloodtothelungswhereitabsorbsoxygenfromtheair,whiletheleftventriclepumpsoxygenatedbloodreturningfromthelungstotherestofbodytosupplythetissues.Physiologistsareconcernedwithestablishingthefactorsresponsiblefortheheartbeat,howtheheartpumpsthebloodaroundthecirculation,andhowitisdistributedtoperfusethetissuesaccordingtotheirneeds.Fluidexchangedbetweenthebloodplasmaandthetissuespassesintothelymphaticsystem,whicheventuallydrainsbackintotheblood.（主要是糖類和脂肪）氧氣頻率的因素是什么？Theenergyrequiredforperformingthevariousactivitiesofthebodyisultimatelyderivedfromrespiration.Thisprocessinvolvestheoxidationoffoodstuffstoreleasetheenergytheycontain.Theoxygenneededforthisprocessisabsorbedfromtheairinthelungsandcarriedtothetissuesbytheblood.Thecarbondioxideproducedbytherespiratoryactivityofthetissuesiscarriedtothelungsbythebloodinthepulmonaryarterywhereitisexcretedintheexpiredair.Thebasicquestionstobeansweredincludethefollowing:Howistheairmovedinandoutofthelungs?Howisthevolumeofairbreathedadjustedtomeettherequirementsofthebody?Whatlimitstherateofoxygenuptakeinthelungs?機體所需營養物質來源于飲食。食物經口腔進入體內，在胃腸道內經酶將其分解成小分何消化的？食物如何被個體分解消化？個體營養物質如何吸收？食物如何在腸內轉運的？Thenutrientsneededbythebodyarederivedfromthediet.Foodistakeninbythemouthandbrokendownintoitscomponentpartsbyenzymesinthegastrointestinaltract.Thedigestiveproductsarethenabsorbedintothebloodacrossthewalloftheintestineandpasstotheliverviatheportalvein.Thelivermakesnutrientsavailabletothetissuesbothfortheirgrowthandrepairandfortheproductionofenergy.Inthecaseofthedigestivesystem,keyphysiologicalquestionsare:Howisfoodingested?Howisitbrokendownanddigested?Howaretheindividualnutrientsabsorbed?Howisthefoodmovedthroughthegut?Howaretheindigestibleremainseliminatedfromthebody?腎臟主要功能是控制細胞外液體的形成。在這一過程中，腎臟也會把不可揮發的廢物排應對像脫水這樣的應激反應？以及尿液可以存儲和排出體外的機制是什么？12.Thechieffunctionofthekidneysistocontrolthecompositionoftheextracellularfluid.Inthecourseofthisprocess,theyalsoeliminatenon-volatilewasteproductsfromtheblood.Toperformthesefunctions,thekidneysproduceurineofvariablecompositionwhichistemporarilystoredinthebladderbeforevoiding.Thekeyphysiologicalquestionsinthiscaseare:howdothekidneysregulatethecompositionoftheblood?Howdotheyeliminatetoxicwaste?Howdotheyrespondtostressessuchasdehydration?Whatmechanismsallowthestorageandeliminationoftheurine?Thereproductivesystem13.生殖是活生物體的一個基本特征。生殖腺產生專門的性細胞，被稱為配子。性生殖的核心是雌雄配子即精子和卵子的產生和融合，因此兩個獨立個體的基因特征融合而產生一個基因上與雙親不同的后代。13.Reproductionisoneofthefundamentalcharacteristicsoflivingorganisms.Thegonadsproducespecializedsexcellsknownasgametes.Atthecoreofsexualreproductionisthecreationandfusionofthemaleandfemalegametes,thespermandova(eggs),withtheresultthatthegeneticcharacteristicsoftwoseparateindividualsaremixedtoproduceoffspringthatdiffergeneticallyfromtheirparents.14.這一系統由骨、骨骼肌、關節和它們的相關組織組成。其主要功能是提供運動需要，維分泌系統和神經系統14.Thisconsistsofthebonesoftheskeleton,skeletalmuscles,joints,andtheirassociatedtissues.Itsprimaryfunctionistoprovideameansofmovement,whichisrequiredforlocomotion,forthemaintenanceofposture,andforbreathing.ItalsoprovidesphysicalsupportfortheinternalorgansHerethemechanismofmusclecontractionisacentralissue.Theendocrineandnervoussystems15.不同器官系統的活動需要協作和調節，以便共同作用滿足機體需要。人體有兩大調節系15.Theactivitiesofthedifferentorgansystemsneedtobecoordinatedandregulatedsothattheyacttogethertomeettheneedsofthebody.Twocoordinatingsystemshaveevolved:thenervoussystemandtheendocrinesystem.Thenervoussystemuseselectricalsignalstotransmitinformationveryrapidlytospecificcells.Thusthenervespasselectricalsignalstotheskeletalmusclestocontroltheircontraction.Theendocrinesystemsecreteschemicalagents,hormones,whichtravelinthebloodstreamtothecellsuponwhichtheyexertaregulatoryeffect.Hormonesplayamajorroleintheregulationofmanydifferentorgansandareparticularlyimportantintheregulationofthemenstrualcycleandotheraspectsofreproduction.16.免疫系統通過殺死入侵的有機體，清除致病或損傷細胞為機體提供防御功能。Theimmunesystemprovidesthedefensesagainstinfectionbothbykillinginvadingorganismsandbyeliminatingdiseasedordamagedcells.Althoughitishelpfultostudyhoweachorganperformsitsfunctions,itisessentialtorecognizethattheactivityofthebodyasawholeisdependentontheintricateinteractionsbetweenthevariousorgansystems.Ifonepartfails,theconsequencesarefoundinotherorgansystemsthroughoutthewholebody.Forexample,ifthekidneysbegintofail,theregulationoftheinternalenvironmentisimpairedwhichinturnleadstodisordersoffunctionelsewhere.各種復雜機制共同作用調節細胞外液的形成，不同個體細胞有自身機制調節內在組成成被稱為穩態，它是機體能夠正常發揮作用所必須的。18.Complexmechanismsareatworktoregulatethecompositionoftheextracellularfluidandindividualcellshavetheirownmechanismsforregulatingtheirinternalcomposition.Theregulatorymechanismsstabilizetheinternalenvironmentdespitevariationsinboththeexternalworldandtheactivityoftheanimal.Theprocessofstabilizationoftheinternalenvironmentiscalledhomeostasisandisessentialifthecellsofthebodyaretofunctionnormally.例如，心臟的跳動依賴于心肌細胞有節律的收縮。這一活動依賴于電信號，而電信號反子的濃度就必須控制在一定范圍內。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，一般來說，機體體重是基本不變的。這類個體可以說處于Inthecourseofaday,anadultconsumesapproximately1kgoffoodanddrinkslitersoffluid.Inamonth,thisisequivalenttoaround30kgoffoodandlitersoffluid.Yet,ingeneral,bodyweightremainsremarkablyconstant.Suchindividualsaresaidtobeinbalance;theintakeoffoodanddrinkmatchestheamountsusedtogenerateenergyfornormalbodilyactivitiesplusthelossesinurineandfeces.Insomecircumstances,suchasstarvation,intakedoesnotmatchtheneedsofthebodyandmuscletissueisbrokendowntoprovideglucoseforthegenerationofenergy.Here,theintakeofproteinislessthantherateofbreakdownandtheindividualissaidtohaveanegativenitrogenbalance.Equally,ifthebodytissuesarebeingbuiltup,asisthecaseforgrowingchildren,pregnantwomenandathletesintheearlystagesoftraining,thedailyintakeofproteinisgreaterthanthenormalbodyturnoverandtheindividualisinpositivenitrogenbalance.平衡的概念可以應用到機體的任何構成成分上，包括水和鹽，而且平衡在機體調節其自4-5mmol.l–1.進食后不久，血糖含量超過這一范圍，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存。Thisconceptofbalancecanbeappliedtoanyofthebodyconstituentsincludingwaterandsaltandisimportantinconsideringhowthebodyregulatesitsowncomposition.Intakemustmatchrequirementsandanyexcessmustbeexcretedforbalancetobemaintained.Additionally,foreachchemicalconstituentofthebodythereisadesirableconcentrationrange,whichthecontrolmechanismsareadaptedtomaintain.Forexample,theconcentrationofglucoseintheplasmaisaboutmmol.l–1betweenmeals.Shortlyafterameal,plasmaglucoserisesabovethislevelandthisstimulatesthesecretionofthehormoneinsulinbythepancreas,whichactstobringtheconcentrationdown.Astheconcentrationofglucosefalls,sodoesthesecretionofinsulin.Ineachcase,thechangesinthecirculatinglevelofinsulinacttomaintaintheplasmaglucoseatanappropriatelevel.Thistypeofregulationisknownasnegativefeedback.Duringtheperiodofinsulinsecretion,theglucoseisbeingstoredaseitherglycogenorfat.負反饋環是在機體出現紊亂時，將一些變量控制在限定范圍內的一個控制系統。雖然上加熱器關閉。anegativefeedbackloopisacontrolsystemthatactstomaintainthelevelofsomevariablewithinagivenrangefollowingadisturbance.Althoughtheexamplegivenabovereferstoplasmaglucose,thebasicprinciplecanbeappliedtootherphysiologicalvariablessuchasbodytemperature,bloodpressure,andtheosmolalityoftheplasma.anegativefeedbacklooprequiresasensorofsomekindthatrespondstothevariableinquestionbutnottootherphysiologicalbariables,thusanosmoreceptorshouldrespindtochangesinosmolalityofthebodyfluidsbutnottochangesinbodytemperatureorbloodpressure.theinformationfromthesensormustbecomparedinsomewaywiththedesiredlevelbysomeformofcomparator.ifthetwodonotmatch,anerrorsignalistransmittedtoaneffector,asystemthatcanacttorestorethevariabletoitsdesiredlevel.thesefeaturesofnegativefeedbackcanbeappreciatedbyexaminingasimpleheatingsystem.thecontrolledvariableisroomtemperature,whichissensedbyathermostat.theeffectorisaheaterofsomekind.whentheroomtemperaturefallsbelowthesetpoint,thetemperaturedifferenceisdetectedbythethermostatwhichswitchesontheheater.thisheatstheroomuntilthetemperaturereachesthepersetlevelwhereupontheheaterisswitchedoff.23.總而言之，機體實際上是由100萬億細胞有序組成了不同的功能結構，其中一些被稱為致疾病的發生。23.Tosumarize,thebodyisactuallyasocialorderofabout100trillioncellsorganizedintodifferentfunctionalstructures,someofwhicharecalledorgans.eachfunctionalstructuresitssharetothemaintenanceofhomeostaticconditionsintheextracellularfluid,whichiscalledtheinternalenvironment.aslongasnormalconditionsaremaintainedinthisinternalenvironment,thecellsofthebodycontinuetoliveandfunctionproperly.Eachcellbenefitsfromhomeostasis,andinturn,eachcellcontributesitssharetowardthemaintenanceofhomeostasis.Thisreciprocalinterplayprovidescontinuousautomaticityofthebodyuntiloneormorefunctionalsystemslosetheirabilitytocontributetheirshareoffunction.Whenthishappens,allthecellsofthebodysuffer.Extremedysfunctionleadstodeath;moderatedysfunctionleadstosickness.,是兩個心房的同時收縮Thecardiaccycleisthesequenceofeventsinoneheartbeat.Initssimplestform,thecardiaccycleisthesimultaneouscontractionofthetwoatria,followedafractionofasecondlaterbythesimultaneouscontractionofthetwoventricles.Thereis,however,asignificantdifferencebetweenthemovementofbloodfromtheatriatotheventricles,andthemovementofbloodfromtheventriclestothearteries.血液的壓力會打開左右房室瓣。兩個心房里三分之二的血液被動地流入到心室中;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血液繼續流入心房，循環重新開始。Followingtheircontraction,theatriarelaxandtheventriclesbegintocontract.VentricularcontractionforcesbloodagainsttheflapsoftherightandleftAVvalvesandclosesthem;theforceofbloodalsoopenstheaorticandpulmonarysemilunarvalves.Astheventriclescontinuetocontract,theypumpbloodintothearteries.Thebloodthatentersthearteriesmustallbepumped.Theventriclesthenrelax,andatthesametimebloodcontinuestoflowintotheatria,andthecyclewillbeginagain.這里一個重要的不同點就是大部分血液是被動地從心房流入心室,但是所有注入動脈的血液均由心室主動射出。因此,對生存來說，心室的正常工作遠比心房的工作重要的多。Theimportantdistinctionhereisthatmostbloodflowspassivelyfromatriatoventricles,butallbloodtothearteriesisactivelypumpedbytheventricles.Forthisreason,theproperfunctioningoftheventriclesismuchmorecrucialtosurvivalthanisatrialfunctioning.收縮的另一個術語是心臟收縮。松弛的術語是心臟舒張。您可能比較熟悉這些術語，因為,張。Thereisanothertermforcontraction,andthatissystole.Thetermforrelaxationisdiastole.Youareprobablyfamiliarwiththesetermsastheyrelatetobloodpressurereadings.Ifweapplythemtothecardiaccycle,wecansaythatatrialsystoleisfollowedbyventricularsystole.Anotherwaytoputitisthatwhentheatriaareinsystole,theventriclesareindiastole,andwhentheventriclesareinsystole,theatriaareindiastole.列精確的活動組成，這些活動使血液從靜脈流過心臟最后再注入動脈。Youmaybeasking:allthisinoneheartbeat?Theanswerisyes.Thecardiaccycleisthisprecisesequenceofeventsthatkeepsbloodmovingfromtheveins,throughtheheartandintothearteries.7.心臟血液循環同時產生心:每一次心跳會有兩個聲音用聽診器可以聽見。第一,最大也最長,是由心室收縮閉合房室瓣而引起的。第二聲是由動脈和肺的半月瓣的閉合造成的。如果任一瓣膜閉合不全,就會聽見另外一個聲音，稱為―心臟雜音‖。Thecardiaccyclealsocreatestheheartsounds:eachheartbeatproducestwosounds,whichcanbeheardwithastethoscope.Thefirstsound,theloudestandlongest,iscausedbyventricularsystoleclosingtheAVvalves.Thesecondsoundiscausedbytheclosureoftheaorticandpulmonarysemi-lunarvalves.Ifanyofthevalvesdonotcloseproperly,anextrasoundcalledaheartmurmurmaybeheard. 心臟的傳導途徑非由神經脈沖引起。心臟自行跳動，腦電脈沖沿一確定路徑穿過心肌層。Thecardiaccycleisasequenceofmechanicaleventsthatisregulatedbytheelectricalactivityofthemyocardium.Cardiacmusclecellshavetheabilitytocontractspontaneously,thatis,nerveimpulsesarenotrequiredtocausecontraction.Theheartgeneratesitsownbeat,andtheelectricalimpulsesfollowaveryspecificroutethroughoutthemyocardium.心臟的自然起搏器是竇房結，它是位于右心房壁上的特化心肌細胞群。竇房結被認為是特化的是因為它有最快的收縮速度。Thenaturalpacemakeroftheheartisthesinoatrial(SA)node,aspecializedgroupofcardiacmusclecellslocatedinthewalloftherightatrium.TheSAnodeisconsideredspecializedbecauseithasthemostrapidrateofcontraction,thatis,itdepolarizesmorerapidlythananyotherpartofthemyocardium.收縮脈沖從竇房結運行到房室結，房室結位于心房間隔膜區下部。從竇房結和房室結到心房心肌層的其余部分的脈沖傳導可引起心房收縮。FromtheSAnode,impulsesforcontractiontraveltotheatrioventricularnode,locatedinthelowerinteratrialseptum.ThetransmissionofimpulsesfromtheSAnodeandAVnodetotherestoftheatrialmyocardiumbringsaboutatrialsystole.它接收來自房室結的脈沖，并傳給左右神經束支。脈沖從神經束支開始，沿著普肯野纖維到達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。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被阻礙而引發IftheSAnodedoesnotfunctionproperly,theAVnodewillinitiatetheheartbeat,butataslowerrate(50to60beatsperminute).TheBundleofHisisalsocapableofgeneratingthebeatoftheventricles,butatamuchslowerrate(15to40beatsperminute).Thismayoccurincertain13.心率失常是不規則的心跳它們的影響范圍小到對人體無害大到威而且可能是因為過多攝入了完全無法泵出血液的心室悸實Arrhythmiasareirregularheartbeats;theireffectsrangefromharmlesstolife-threatening.Nearlyeveryoneexperiencesheartpalpitationsfromtimetotime.Theseareusuallynotserious,andmaybetheresultoftoomuchcaffeine,nicotine,oralcohol.Muchmoreseriousisventricularfibrillation,averyrapidanduncoordinatedventricularbeatthatistotallyineffectiveforpumpingblood.心率6080下，是竇房結去極化的速度。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問題上來，設定一個人擁有良好的健康狀況。正如你所知，一個身體狀態良好的運動員的心率較低。那些籃球運動員的脈搏在每分鐘50次左右，馬拉松3540持續的運動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60毫升。下面這個簡單的公式能使我們很容易計算出心輸出Inordertocalculatecardiacoutput,wemustknowthepulserateandhowmuchbloodispumpedperbeat.Strokevolumeisthetermfortheamountofbloodpumpedbyaventricleperbeat;anaveragerestingstrokevolumeis60to80mlperbeat.Asimpleformulathenenablesustodeterminecardiacoutput:Cardiacoutput＝Strokevolume×pulse(heartrate)我們假定人安靜時的心室跳動一次的供血量為7070量＝70ml70bpm（每分鐘脈搏次數）＝4900ml/m5L)Letusputintothisformulaanaveragerestingstrokevolume,70ml,andanaveragerestingpulse,70beatsperminute(bpm): Cardiacoutput＝70ml×70bpm Cardiactput＝4,900mlperminute (approximately5liters)當然心輸出量的多少會隨著人體型的大小而變，但人在靜息狀態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下運動員的心臟供血量明顯高于常人。運動員的強有力的心臟每次跳動能為身體提供更多血液。因此，靜息狀態下他們保持一個較低的心率 。 Noticethattheathlete srestingstrokevolumeissignificantlyhigherthantheaverage.Theathlete’smoreefficientheartpumpsmorebloodwitheachbeat,andsocanmaintainanormalrestingcardiacoutputwithfewerbeats.現在我們再考慮一下心臟對運動作何反映。人在運動的過程中心率會加快，心輸出量也心臟供血量的計算公式如下：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)一個健康年輕人每分鐘的心輸出量可以增加到他安靜時的４倍Thisexercisecardiacoutputistwicetherestingcardiacoutputwefirstcalculated,whichshouldnotbeconsideredunusual.Thecardiacoutputofahealthyyoungpersonmayincreaseuptofourtimestherestinglevelduringstrenuousexercise.Thisexercisecardiacoutputistwicetherestingcardiacoutputwefirstcalculated,whichshouldnotbeconsideredunusual.Thecardiacoutputofahealthyyoungpersonmayincreaseuptofourtimestherestinglevelduringstrenuousexercise.心率的調節雖然心臟自行跳動并保持其跳動，但心臟收縮的頻率可根據情況的不同而發生變化。神經系統可以調節心臟收縮的力度并控制心率的必要變Althoughtheheartgeneratesandmaintainsitsownbeat,therateofcontractioncanbechangedtoadapttodifferentsituations.Thenervoussystemcananddoesbringaboutnecessarychangesinheartrateaswellasinforceofcontraction.腦髓質有兩個心血管控制中心：加速中樞和抑制中樞。兩中樞通過自主神經向心臟傳送過迷走神經傳輸到心臟，降低心臟跳動的速率。Themedullaofthebraincontainsthetwocardiaccenters,theacceleratorcenterandtheinhibitorycenter.Thesecenterssendimpulsestotheheartalongautonomicnerves.Theautonomicnervoussystemhastwodivisions:sympatheticandparasympathetic.Sympatheticimpulsesfromtheacceleratorcenteralongsympatheticnervesincreaseheartrateandforceofcontraction.Parasympatheticimpulsesfromtheinhibitorycenteralongthevagusnervesdecreasetheheartrate.我們下一個問題是腦髓質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刺激心率產生相應的變化。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)一個健康年輕人每分鐘的心輸出量可以增加到他安靜時的４倍Thisexercisecardiacoutputistwicetherestingcardiacoutputwefirstcalculated,whichshouldnotbeconsideredunusual.Thecardiacoutputofahealthyyoungpersonmayincreaseuptofourtimestherestinglevelduringstrenuousexercise.Thisexercisecardiacoutputistwicetherestingcardiacoutputwefirstcalculated,whichshouldnotbeconsideredunusual.Thecardiacoutputofahealthyyoungpersonmayincreaseuptofourtimestherestinglevelduringstrenuousexercise.心率的調節雖然心臟自行跳動并保持其跳動，但心臟收縮的頻率可根據情況的不同而發生變化。神經系統可以調節心臟收縮的力度并控制心率的必要變Althoughtheheartgeneratesandmaintainsitsownbeat,therateofcontractioncanbechangedtoadapttodifferentsituations.Thenervoussystemcananddoesbringaboutnecessarychangesinheartrateaswellasinforceofcontraction.腦髓質有兩個心血管控制中心：加速中樞和抑制中樞。兩中樞通過自主神經向心臟傳送過迷走神經傳輸到心臟，降低心臟跳動的速率。Themedullaofthebraincontainsthetwocardiaccenters,theacceleratorcenterandtheinhibitorycenter.Thesecenterssendimpulsestotheheartalongautonomicnerves.Theautonomicnervoussystemhastwodivisions:sympatheticandparasympathetic.Sympatheticimpulsesfromtheacceleratorcenteralongsympatheticnervesincreaseheartrateandforceofcontraction.Parasympatheticimpulsesfromtheinhibitorycenteralongthevagusnervesdecreasetheheartrate.我們下一個問題是腦髓質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刺激心率產生相應化。Ournextquestionmightbe:whatinformationisreceivedbythemedullatoinitiatechanges?Sincetheheartpumpsblood,itisessentialtomaintainnormalbloodpressure.Bloodcontainsoxygen,whichalltissuesmustreceivecontinuously.Therefore,changesinbloodpressureandoxygenlevelofthebloodarestimuliforchangesinheartrate.壓力感受器和化學受體位于頸動脈和主動脈弓。位于頸動脈竇和主動脈竇的壓力感受器些事實集中在一個特例中，我們就可以看出心臟調節是一種反射。Pressoreceptorsandchemoreceptorsarelocatedinthecarotidarteriesandaorticarch.orsinthecarotidsinusesandaorticsinusdetectchangesinbloodpressure.Chemoreceptorsinthecarotidbodiesandaorticbodydetectchangesintheoxygencontentoftheblood.Thesensorynervesforthecarotidreceptorsaretheglossopharyngealnerves;thesensorynervesforaorticarchreceptorsarethevagusnerves.Ifwenowputallthesefactstogetherinaspecificexample,youwillseethattheregulationofheartrateisareflex.一個處于臥位的人突然變為站位，或許會感到一陣稍微的頭暈，這是因為腦部血壓突降這些副交感神經脈沖減緩心率至正常休息頻率。Apersonwhostandsupsuddenlyfromalyingpositionmayfeellight-headedordizzyforafewmoments,becausebloodpressuretothebrainhasdecreasedabruptly.Thedropinbloodpressureisdetectedbypressoreceptorsinthecarotidnoticethattheyare“ontheway”tothebrain,averystrategiclocation.Impulsesgeneratedbythepressoreceptorstrav