Transportmammals.docx

Transportmammals.docx

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Transportmammals

TransportinMammals

1989Paper2Question6

6.（a）WithreferencetoTWOnamedexamples,compareandcontrastanopencirculatorysystemwithaclosedcirculatorysystemintermsoftheirstructuralorganizations,functionaladvantage（s）anddisadvantage（s）.

（10marks）

（b）WithreferencetoTWOnamedexamples,discusstheadvantagesofacompletedoublecirculatorysystemoverasinglecirculatorysystem.（6marks）

（c）Discusstheroleofplasmaproteininthecontroloftissuefluidvolumeinamammal.（4marks）

Ans

1991Paper2Question6

6.Explainthemechanismswhichmaintainanefficientcirculationofbloodinthebodyofamammalwhenatrestandduringintenseactivity.（20marks）

Ans

1992Paper2Question5

5.Comparethetypeofcirculatorysystemfoundinanamedinsectwiththatfoundinanamedmammal.Considertheadvantagesanddisadvantagesofeachtypeofsysteminrelationtogasexchangeandnutrientdistributionwithintheseorganisms.（20marks）

Ans

1993Paper1Question8

8.（a）Inanexperimentperformedonadog,therelationshipbetweencardiacoutputandbloodvolumeoftheleftventriclejustbeforecontractionstartedwasstudied.Thisrelationshipwasstudiedbyartificiallychangingthetotalbloodvolumeoftheanimal,thusalteringtheventricularvolume.TheexperimentwasthenrepeatedwithsimultaneouselectricalstimulationofnerveAwhichinnervatestheheart.Theresultsareshowninthegraphbelow:

（i）Whatconclusionscanbedrawnfromthisexperiment?

（2marks）

（ii）

（1）SuggestaphysiologicalstateoftheanimalthatwouldgiveacardiacresponsesimilartothatproducedbystimulationofnerveA.（1mark）

（2）Whatisthefunctionalsignificanceofsucharesponse?

（1mark）

（iii）InjectionofchemicalXintothecirculationoftheanimalwouldgivearesponsesimilartothatproducedbyelectricalstimulationofnerveA.

（1）SuggestwhatchemicalXis.（1mark）

（2）WhatisthepossiblefunctionalrelationshipbetweenstimulationofnerveAandchemicalXonthefunctioningoftheheart（2marks）

（b）Inanotherexperiment,theheartrateofthedogundereachofthefollowingconditionswasmonitored:

（1）intherestingstate（asthecontrol）,

（2）electricalstimulationofnerveAwhichinnervatestheheart,and

（3）electricalstimulationofnerveBwhichalsoinnervatestheheart.

Theresultsareasfollows:

Restingstate

NerveAstimulation

NerveBstimulation

Heartrate（beats/min）

130

180

100

（i）Statetheeffectsoftheabovenervestimulationsonheartrate.Whatcanyoudeduceaboutthenatureofinnervationstotheheart?

（2marks）

（ii）Outlinethemechanismwhichaffectstheheartrateundereachofthefollowingconditions:

（1）intherestingstate

（2）whennerveAisstimulated

（3）whennerveBisstimulated（4marks）

（iii）WhichpartofthenervoussystemisresponsibleforregulatingtheactivitiesofnervesAandB?

（1mark）

（c）Basedontheresultsofalltheaboveexperiments,summariseyourunderstandingonthemechanismcontrollingcardiacfunction.（3marks）

（d）Howwouldtheheartrateofthedogattherestingstatecomparewiththatofman?

Accountforsuchadifference.（3marks）

Ans

1993Paper2Question2

2.（a）Distinguishbetweendiffusionandactivetransport.（4marks）

（b）Statefourenvironmentalfactorsthatinfluencesaltabsorptioninplants.Explainhoweachexertsitseffect.（6rnarks）

（c）（i）Givethreeexamplesofbodyfunctionsinmammalswhereactivetransportisessential.

（ii）Brieflydescribethefunctionalsignificanceofactivetransportineachcase.

（iii）Withreferencetooneofthefunctionsyouhavementionedin（i）,describehowthestructure（s）concernedis/arestructurallyadaptedtothisfunction.（10marks）

Ans

1993Paper2Question7

7.Giveanaccountoftheroleofbloodintheuptake,transportandreleaseofrespiratorygases.（20marks）

Ans

1995Paper2Question1

1.（a）Describeandexplainhowlymphisformedfromblood.（7marks）

（b）Explaintheimportanceofthelymphaticsysteminmammals.（7marks）

（c）Compareandcontrastgaseousexchangeinahumanadultandfoetus.（6marks）

Ans

1996Paper1Question12

12.Thefollowingfigurepresentsthechangeofpressurewithtimeintheleftatrium,leftventricleandaortaduringtwocardiaccyclesofahealthyyoungmanatrest.

（a）DuringtimeperiodJ,theleftatriumisatdiastole.Describeandaccountforthechangesinatrialpressureduringthisphaseofthecardiaccycle.Nametheheartvalveinvolvedanddescribeitsactivity.（Hint:

Thepressurechangeisrelatedtothebloodflowintheheart.）（4marks）

（b）StatetheactivityoftheleftatriumduringtimeperiodK.Howisthisactivityrelatedtothepressurechangeoftheleftventricleduringthesametimeperiod?

（1marks）

（c）（i）StatetheactivitiesoftheleftventricleduringtimeperiodsMandN.

（ii）Howwouldyouexpectthepressurechangeintherightventricletodifferinmagnitudeascomparedtotheleftventricleduringthesametimeperiods?

Explainyouranswer.（2marks）

（d）DescribethechangesinaorticpressureduringtimeperiodL.Howisthischangerelatedtotheactivitiesoftheleftventricleandbloodflow?

Nametheheartvalveinvolvedanddescribeitsactivity.（4marks）

（e）Howwouldthepeakpressureandfrequencyofthecardiaccyclesshowninthefigurechangeafterthemanhasrunupaflightofstairs?

（1mark）

Total:

13marks

Ans

1997Paper2Question6

6.Describethemechanismsthatbringaboutthemovementofwaterinthetransportsystemsoffloweringplantsandmammals.Statetwoessentialdifferencesregardingthenatureofcontrolwhichaffectswatermovementinfloweringplantsandmammals.（20marks）

Ans

Solution

1989Paper2Question6Solution

6.（a）

Opencirculatorysystem

Closedcirculatorysystem

Examples:

Mostarthropods（insects,crabs）&mostmolluscs（snails,clams）

Allvertebrates&annelids

1

Structuralsimilarities:

Thepresenceoforgan（s）（i.e.heartormodifiedbloodvessel）forthepumpingofblood,andasystemofone－wayvalvestokeepthebloodflowinonedirection

2

Structuraldifferences:

Bloodisnotenclosedwithinasystemofvessels.Afterleavingtheheartandmajorbloodvessels,itflowsintothespace（sinusesorhaemocoel）betweentheinternalorgansandtissues

Bloodisenclosedwithinasystemofbloodvesselsanddoesnotcomeindirectcontractwithothertissues

2

Disadvantages:

Advantages:

Alowpressuresystem.Bloodflowinlow.

Ahighpressuresystem.Bloodflowisfasterandhencethetransportingfunctionismademoreefficient.

2

Distributionofbloodispoorlycontrolled.

Distributionofblood（orcardiacoutput）tovarioustissuescanberegulatedbymeansofmuscle－drivenchangesinvesseldiameter.

2

Advantage:

Disadvantage:

Itdoesnotrequirethedevelopmentofapowerfulpumpingorganforpropulsionofblood.

Itismoredemandingonthehearttogeneratetheforcerequiredtopropelbloodthroughthesystemofvessels.

1

（10）

（b）ExampleB:

fish－singlecirculatorysystem1

Birdsandmammals－doublecirculatorysystemincompletedoublecirculatorysystem,bloodafteroxygenationisreturnedtotheheartandpumpedouttoothertissuesunderhighpressure.1

Thehigherbloodpressureincreasesflowrateandhenceallowsthetransportingfunctiontobecarriedoutmoreefficiently.1

Thefiltrationandremovalofwastebytheglomeruliofthekidneybecomemoreefficient.1

Theseenabletheorganismconcernedtohaveahighermetabolicrate1

Theheartissuppliedwithoxygenatedbloodinsteadofdeoxygenatedbloodinreturn,itcanpumpmoreforcefullytogeneratehigherbloodpressureandflowrate.1

（6）

（c）Plasmaproteinsaremacromoleculesandmostofthemaretoolargetopassthroughthewallofcapillaries1

Asaresulttheygiverisetoacolloidalosmoticpressurewhichishigherforplasmathanfortissuefluid.1

Thegradientofcolloidalosmoticpressureatthevenousendfavorsnetreabsorptionoftissuefluidfrominterstitialspaceintocapillaries.

Itisimportantincounteractingthehydrostaticpressuregradientatarterioleendwhichbringsabouttissuefluidformationbydrivingfluidoutfromcapillariesintotheinterstitialspace.2

（4）

1991Paper2Question6Solution

6.Restingcondition/normalactivities:

（10）

－heart:

－myocardialrhythm

－pacemaker:

actionofSAnode,AVnodeandPurkinjefibers

－characteristicsofcardiacmuscle:

notfatigued

－contractionofheartcreatedapressure（systolicpressure=120mmHg）forcingbloodintothearteries

－distendingtheelasticwallofthearterieswhichrecoilandpushbloodforward（diastolicpressure=80mmHg）

－semilunarvalvespreventbackflowofbloodintotheheart

－venousbloodflowmaintainedby:

a.residualheartpressure

b.contractionofadjacentskeletalmuscles

c.valvespreventingbackflow

d.inspiratorymovementofthechest

e.hydrostaticpressureoftissuefluid

Controlofcirculationtoadjusttodifferentphysicalstatesofactivity:

（10）

Controlofheartbeat（cardiacrhythm）

－cardiovascularcenter（withinthemedullaofthebrain）accelerates/deceleratestheheartratebysendingnerveimpulsesalongthesympathetic/parasympathetic（vagus）nervetothepacemaker

－whichnervebeingstimulateddependsonfactorslike:

pH,CO2concentrationofblood（sensedbychemoreceptorsinbloodvessel）,bloodpressure（sensedbybaroreceptorsinbloodvessel）wh