IntroductiontoPhysiologyIntroductionPhysiologyisthestudyofthefunctionsoflivingmatter.Itisconcernedwithhowanorganismperformsitsv ariedactivities:howitfeeds,howitmoves,howitadaptstochangingcircumstances,howitspawnsnewgenerati ons.Thesubjectisvastandembracesthewholeoflife.Thesuccessofphysiologyinexplaininghoworganismsp erformtheirdailytasksisbasedonthenotionthattheyareintricateandexquisitemachineswhoseoperationisgo vernedbythelawsofphysicsandchemistry.Althoughsomeprocessesaresimilaracrossthewholespectrumofbiology—thereplicationofthegenetic codefororexample—manyarespecifictoparticulargroupsoforganisms.Forthisreasonitisnecessarytodivid ethesubjectintovariouspartssuchasbacterialphysiology,plantphysiology,andanimalphysiology.Tostudyhowananimalworksitisfirstnecessarytoknowhowitisbuilt.Afullappreciationofthephysiolog yofanorganismmustthereforebebasedonasoundknowledgeofitsanatomy.Experimentscanthenbecarriedo uttoestablishhowparticularpartsperformtheirfunctions.Althoughtherehavebeenmanyimportantphysiolo gicalinvestigationsonhumanvolunteers,theneedforprecisecontrolovertheexperimentalconditionshasmea ntthatmuchofourpresentphysiologicalknowledgehasbeenderivedfromstudiesonotheranimalssuchasfrog s,rabbits,cats,anddogs.Whenitisclearthataspecificphysiologicalprocesshasacommonbasisinawidevariet yofanimalspecies,itisreasonabletoassumethatthesameprincipleswillapplytohumans.Theknowledgegain edfromthisapproachhasgivenusagreatinsightintohumanphysiologyandendoweduswithasolidfoundation fortheeffectivetreatmentofmanydiseases.Thebuildingblocksofthebodyarethecells,whicharegroupedtogethertoformtissues.Theprincipaltype softissueareepithelial,connective,nervous,andmuscular,eachwithitsowncharacteristics.Manyconnective tissueshaverelativelyfewcellsbuthaveanextensiveextracellularmatrix.Incontrast,smoothmuscleconsists anssuchasthebrain,theh eart,thelungs,theintestines,andtheliverareformedbytheaggregationofdifferentkindsoftissues.Theorgans arethemselvespartsofdistinctphysiologicalsystems.Theheartandbloodvesselsformthecardiovascularsyst em;thelungs,trachea,andbronchitogetherwiththechestwallanddiaphragmformtherespiratorysystem;thes keletonandskeletalmusclesformthemusculoskeletalsystem;thebrain,spinalcord,autonomicnervesandgan glia,andperipheralsomaticnervesformthenervoussystem,andsoon.Cellsdifferwidelyinformandfunctionbuttheyallhavecertaincommoncharacteristics.Firstly,theyareb oundedbyalimitingmembrane,theplasmamembrane.Secondly,theyhavetheabilitytobreakdownlargemol eculestosmalleronestoliberateenergyfortheiractivities.Thirdly,atsomepointintheirlifehistory,theyposses sanucleuswhichcontainsgeneticinformationintheformofdeoxyribonucleicacid(DNA).Livingcellscontinuallytransformmaterials.Theybreakdownglucoseandfatstoprovideenergyforother activitiessuchasmotilityandthesynthesisofproteinsforgrowthandrepair.Thesechemicalchangesarecollect ivelycalledmetabolism.Thebreakdownoflargemoleculestosmalleronesiscalledcatabolismandthesynthes isoflargemoleculesfromsmalleronesanabolism.Inthecourseofevolution,cellsbegantodifferentiatetoservedifferentfunctions.Somedevelopedtheabil itytocontract(musclecells),otherstoconductelectricalsignals(nervecells).Afurthergroupdevelopedtheabi litytosecretedifferentsubstancessuchashormonesorenzymes.Duringembryologicaldevelopment,thispro cessofdifferentiationisre-enactedasmanydifferenttypesofcellareformedfromthefertilizedegg.Mosttissuescontainamixtureofcelltypes.Forexample,bloodconsistsofredcells,whitecells,andplatele ts.Redcellstransportoxygenaroundthebody.Thewhitecellsplayanimportantroleindefenseagainstinfection 生理学简介介绍生理学是研究生物体功能的科学。

它研究生物体如何进行各种活动，如何饮食，如何运动，如何适应不断改变的环境，如何繁殖后代。

这门学科包罗万象，涵盖了生物体整个生命过程。

生理学成功地andtheplateletsarevitalcomponentsintheprocessofbloodclotting.Thereareanumberofdifferenttypesofcon nectivetissuebutallarecharacterizedbyhavingcellsdistributedwithinanextensivenoncellularmatrix.Nerve tissuecontainsnervecellsandglialcells.ThePrincipalOrganSystemsThecardiovascularsystemThecellsoflargemulticellularanimalscannotderivetheoxygenandnutrientstheyneeddirectlyfromthee xternalenvironment.Theoxygenandnutrientsmustbetransportedtothecells.Thisisoneoftheprincipalfuncti onsoftheblood,whichcirculateswithinbloodvesselsbyvirtueofthepumpingactionoftheheart.Theheart,blo odvessels,andassociatedtissuesformthecardiovascularsystem.Theheartconsistsoffourchambers,twoatriaandtwoventricles,whichformapairofpumpsarrangedside byside.Therightventriclepumpsdeoxygenatedbloodtothelungswhereitabsorbsoxygenfromtheair,whileth eleftventriclepumpsoxygenatedbloodreturningfromthelungstotherestofbodytosupplythetissues.Physiol ogistsareconcernedwithestablishingthefactorsresponsiblefortheheartbeat,howtheheartpumpsthebloodar oundthecirculation,andhowitisdistributedtoperfusethetissuesaccordingtotheirneeds.Fluidexchangedbet weenthebloodplasmaandthetissuespassesintothelymphaticsystem,whicheventuallydrainsbackintothebl ood.TherespiratorysystemTheenergyrequiredforperformingthevariousactivitiesofthebodyisultimatelyderivedfromrespiratio n.Thisprocessinvolvestheoxidationoffoodstuffstoreleasetheenergytheycontain.Theoxygenneededforthi sprocessisabsorbedfromtheairinthelungsandcarriedtothetissuesbytheblood.Thecarbondioxideproduced bytherespiratoryactivityofthetissuesiscarriedtothelungsbythebloodinthepulmonaryarterywhereitisexcre tedintheexpiredair.Thebasicquestionstobeansweredincludethefollowing:Howistheairmovedinandoutoft helungsHowisthevolumeofairbreathedadjustedtomeettherequirementsofthebodyWhatlimitstherateofox ygenuptakeinthelungsThedigestivesystemThenutrientsneededbythebodyarederivedfromthediet.Foodistakeninbythemouthandbrokendownin toitscomponentpartsbyenzymesinthegastrointestinaltract.Thedigestiveproductsarethenabsorbedintothe bloodacrossthewalloftheintestineandpasstotheliverviatheportalvein.Thelivermakesnutrientsavailableto thetissuesbothfortheirgrowthandrepairandfortheproductionofenergy.Inthecaseofthedigestivesystem,ke yphysiologicalquestionsare:HowisfoodingestedHowisitbrokendownanddigestedHowaretheindividualn utrientsabsorbedHowisthefoodmovedthroughthegutHowaretheindigestibleremainseliminatedfromtheb odyThekidneysandurinarytractThechieffunctionofthekidneysistocontrolthecompositionoftheextracellularfluid.Inthecourseofthis process,theyalsoeliminatenon-volatilewasteproductsfromtheblood.Toperformthesefunctions,thekidney sproduceurineofvariablecompositionwhichistemporarilystoredinthebladderbeforevoiding.Thekeyphysi ologicalquestionsinthiscaseare:howdothekidneysregulatethecompositionofthebloodHowdotheyelimina tetoxicwasteHowdotheyrespondtostressessuchasdehydrationWhatmechanismsallowthestorageandelim inationoftheurineThereproductivesystem 解释了生物体如何进行日常活动，基于的观点是生物体好比是结构复杂而灵巧的机器，其操作受物理和化学规律控制。