完整word版药学英语第五版原文翻译.docx

完整word版药学英语第五版原文翻译.docx

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完整word版药学英语第五版原文翻译

IntroductiontoPhysiology

Introduction

Physiologyisthestudyofthefunctionsoflivingmatter。

Itisconcernedwithhowanorganismperformsitsvariedactivities：

howitfeeds，howitmoves,howitadaptstochangingcircumstances，howitspawnsnewgenerations.Thesubjectisvastandembracesthewholeoflife.Thesuccessofphysiologyinexplaininghoworganismsperformtheirdailytasksisbasedonthenotionthattheyareintricateandexquisitemachineswhoseoperationisgovernedbythelawsofphysicsandchemistry.

Althoughsomeprocessesaresimilaracrossthewholespectrumofbiology—thereplicationofthegeneticcodefororexample-manyarespecifictoparticulargroupsoforganisms.Forthisreasonitisnecessarytodividethesubjectintovariouspartssuchasbacterialphysiology,plantphysiology，andanimalphysiology.

Tostudyhowananimalworksitisfirstnecessarytoknowhowitisbuilt.Afullappreciationofthephysiologyofanorganismmustthereforebebasedonasoundknowledgeofitsanatomy。

Experimentscanthenbecarriedouttoestablishhowparticularpartsperformtheirfunctions.Althoughtherehavebeenmanyimportantphysiologicalinvestigationsonhumanvolunteers,theneedforprecisecontrolovertheexperimentalconditionshasmeantthatmuchofourpresentphysiologicalknowledgehasbeenderivedfromstudiesonotheranimalssuchasfrogs，rabbits,cats，anddogs.Whenitisclearthataspecificphysiologicalprocesshasacommonbasisinawidevarietyofanimalspecies,itisreasonabletoassumethatthesameprincipleswillapplytohumans.Theknowledgegainedfromthisapproachhasgivenusagreatinsightintohumanphysiologyandendoweduswithasolidfoundationfortheeffectivetreatmentofmanydiseases.

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.

Cellsdifferwidelyinformandfunctionbuttheyallhavecertaincommoncharacteristics。

Firstly，theyareboundedbyalimitingmembrane，theplasmamembrane.Secondly，theyhavetheabilitytobreakdownlargemoleculestosmalleronestoliberateenergyfortheiractivities.Thirdly,atsomepointintheirlifehistory，theypossessanucleuswhichcontainsgeneticinformationintheformofdeoxyribonucleicacid（DNA）.

Livingcellscontinuallytransformmaterials.Theybreakdownglucoseandfatstoprovideenergyforotheractivitiessuchasmotilityandthesynthesisofproteinsforgrowthandrepair.Thesechemicalchangesarecollectivelycalledmetabolism.Thebreakdownoflargemoleculestosmalleronesiscalledcatabolismandthesynthesisoflargemoleculesfromsmalleronesanabolism。

Inthecourseofevolution，cellsbegantodifferentiatetoservedifferentfunctions.Somedevelopedtheabilitytocontract（musclecells），otherstoconductelectricalsignals（nervecells）。

Afurthergroupdevelopedtheabilitytosecretedifferentsubstancessuchashormonesorenzymes.Duringembryologicaldevelopment,thisprocessofdifferentiationisre—enactedasmanydifferenttypesofcellareformedfromthefertilizedegg。

Mosttissuescontainamixtureofcelltypes.Forexample,bloodconsistsofredcells,whitecells，andplatelets。

Redcellstransportoxygenaroundthebody。

Thewhitecellsplayanimportantroleindefenseagainstinfectionandtheplateletsarevitalcomponentsintheprocessofbloodclotting.Thereareanumberofdifferenttypesofconnectivetissuebutallarecharacterizedbyhavingcellsdistributedwithinanextensivenoncellularmatrix.Nervetissuecontainsnervecellsandglialcells。

ThePrincipalOrganSystems

Thecardiovascularsystem

Thecellsoflargemulticellularanimalscannotderivetheoxygenandnutrientstheyneeddirectlyfromtheexternalenvironment。

Theoxygenandnutrientsmustbetransportedtothecells.Thisisoneoftheprincipalfunctionsoftheblood，whichcirculateswithinbloodvesselsbyvirtueofthepumpingactionoftheheart。

Theheart,bloodvessels,andassociatedtissuesformthecardiovascularsystem。

Theheartconsistsoffourchambers，twoatriaandtwoventricles,whichformapairofpumpsarrangedsidebyside.Therightventriclepumpsdeoxygenatedbloodtothelungswhereitabsorbsoxygenfromtheair，whiletheleftventriclepumpsoxygenatedbloodreturningfromthelungstotherestofbodytosupplythetissues。

Physiologistsareconcernedwithestablishingthefactorsresponsiblefortheheartbeat,howtheheartpumpsthebloodaroundthecirculation，andhowitisdistributedtoperfusethetissuesaccordingtotheirneeds。

Fluidexchangedbetweenthebloodplasmaandthetissuespassesintothelymphaticsystem，whicheventuallydrainsbackintotheblood.

Therespiratorysystem

Theenergyrequiredforperformingthevariousactivitiesofthebodyisultimatelyderivedfromrespiration。

Thisprocessinvolvestheoxidationoffoodstuffstoreleasetheenergytheycontain。

Theoxygenneededforthisprocessisabsorbedfromtheairinthelungsandcarriedtothetissuesbytheblood。

Thecarbondioxideproducedbytherespiratoryactivityofthetissuesiscarriedtothelungsbythebloodinthepulmonaryarterywhereitisexcretedintheexpiredair。

Thebasicquestionstobeansweredincludethefollowing:

Howistheairmovedinandoutofthelungs？

Howisthevolumeofairbreathedadjustedtomeettherequirementsofthebody？

Whatlimitstherateofoxygenuptakeinthelungs？

Thedigestivesystem

Thenutrientsneededbythebodyarederivedfromthediet.Foodistakeninbythemouthandbrokendownintoitscomponentpartsbyenzymesinthegastrointestinaltract。

Thedigestiveproductsarethenabsorbedintothebloodacrossthewalloftheintestineandpasstotheliverviatheportalvein.Thelivermakesnutrientsavailabletothetissuesbothfortheirgrowthandrepairandfortheproductionofenergy。

Inthecaseofthedigestivesystem,keyphysiologicalquestionsare：

Howisfoodingested?

Howisitbrokendownanddigested？

Howaretheindividualnutrientsabsorbed？

Howisthefoodmovedthroughthegut?

Howaretheindigestibleremainseliminatedfromthebody？

Thekidneysandurinarytract

Thechieffunctionofthekidneysistocontrolthecompositionoftheextracellularfluid.Inthecourseofthisprocess,theyalsoeliminatenon—volatilewasteproductsfromtheblood。

Toperformthesefunctions，thekidneysproduceurineofvariablecompositionwhichistemporarilystoredinthebladderbeforevoiding。

Thekeyphysiologicalquestionsinthiscaseare：

howdothekidneysregulatethecompositionoftheblood?

Howdotheyeliminatetoxicwaste？

Howdotheyrespondtostressessuchasdehydration？

Whatmechanismsallowthestorageandeliminationoftheurine？

Thereproductivesystem

Reproductionisoneofthefundamentalcharacteristicsoflivingorganisms。

Thegonadsproducespecializedsexcellsknownasgametes。

Atthecoreofsexualreproductionisthecreationandfusionofthemaleandfemalegametes，thespermandova（eggs），withtheresultthatthegeneticcharacteristicsoftwoseparateindividualsaremixedtoproduceoffspringthatdiffergeneticallyfromtheirparents.

Themusculoskeletalsystem

Thisconsistsofthebonesoftheskeleton,skeletalmuscles，joints,andtheirassociatedtissues。

Itsprimaryfunctionistoprovideameansofmovement,whichisrequiredforlocomotion，forthemaintenanceofposture，andforbreathing.Italsoprovidesphysicalsupportfortheinternalorgans。

Herethemechanismofmusclecontractionisacentralissue。

Theendocrineandnervoussystems.

Theendocrineandnervoussystems

Theactivitiesofthedifferentorgansystemsneedtobecoordinatedandregulatedsothattheyacttogethertomeettheneedsofthebody。

Twocoordinatingsystemshaveevolved:

thenervoussystemandtheendocrinesystem。

Thenervoussystemuseselectricalsignalstotransmitinformationveryrapidlytospecificcells.Thusthenervespasselectricalsignalstotheskeletalmusclestocontroltheircontraction。

Theendocrinesystemsecreteschemicalagents,hormones,whichtravelinthebloodstreamtothecellsuponwhichtheyexertaregulatoryeffect.Hormonesplayamajorroleintheregulationofmanydifferentorgansandareparticularlyimportantintheregulationofthemenstrualcycleandotheraspectsofreproduction.

Theimmunesystemprovidesthebody’sdefensesagainstinfectionbothbykillinginvadingorganismsandbyeliminatingdiseasedordamagedcells.

Althoughitishelpfultostudyhoweachorganperformsitsfunctions,itisessentialtorecognizethattheactivityofthebodyasawholeisdependentontheintricateinteractionsbetweenthevariousorgansystems.Ifonepartfails,theconsequencesarefoundinotherorgansystemsthroughoutthewholebody.Forexample，ifthekidneysbegintofail,theregulationoftheinternalenvironmentisimpairedwhichint