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IntroductiontoPhysiologyIntroductionPhysiologyisthestudyofthefunctionsoflivingmatter.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.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。尽管从生物学整个范畴看，生物体某些活动过程是相似的——如基因编码的复制——但许多过程还是某些生物体群组特有的。鉴于此有必要将这门学科分成不同部分研究，如细菌生理学、植物生理学和动物生理学。要研究一种动物如何活动，首先需要了解它的构成。要充分了解一个生物体的生理学活动就必须掌握全面的解剖学知识。一个生物体的各部分起着什么作用可通过实验观察得知。尽管我们对志愿者进行了许多重要的生理调查，但是实验条件需要精确控制，所以我们当前大多生理知识还是源于对其它动物如青蛙，兔子，猫和狗等的研究。当我们明确大多数动物物种的特定生理过程存在共同之处时，相同的生理原理适用于人类也是合理的。通过这种方法，我们获得了大量的知识，从而让我们对人类生理学有了更深入的了解，为我们有效治疗许多疾病提供了一个坚实的基础。机体的基本组成物质是细胞，细胞结合在一起形成组织。组织的基本类型有上皮组织，结缔组织，神经组织和肌组织，每类组织都有各自的特征。许多结缔组织中细胞量相对较少，但是有大量的细胞外基质。相比而言，光滑的肌组织由大量密密麻麻的肌细胞通过特定的细胞连接组成。各种器官如脑，心脏，肺，小肠和肝等由不同种类的组织聚集而成。这些器官是不同生理系统的组成部分。心脏和血管组成心血管系统；肺，器官，支气管，胸壁和膈肌组成呼吸系统；骨骼和骨骼肌组成骨骼肌系统；大脑，脊髓，自主神经和神经中枢以及周围躯体神经组成神经系统等等。细胞在形体和功能上差异很大，但是它们有某些共同的特征。第一，它们由限制膜包被，即细胞质膜；第二，细胞有把大分子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.ThePrincipalOrganSystemsThecardiovascularsystemThecellsoflargemulticellularanimalscannotderivetheoxygenandnutrientstheyneeddirectlyfromtheexternalenvironment.Theoxygenandnutrientsmustbetransportedtothecells.Thisisoneoftheprincipalfunctionsoftheblood,whichcirculateswithinbloodvesselsbyvirtueofthepumpingactionoftheheart.Theheart,bloodvessels,andassociatedtissuesformthe