IB Biology Notes for Digestion, Circulation & Respirationtfssbio.pbworks.com/f/Dig Circ Resp...

IBBiology NotesforDigestion,Circulation&Respiration

A.DeJong/TFSS2009

TheinformationinthisdocumentismeanttocoverTopic6.1,6.2&6.4intheIBSyllabus.DigestionWhyisdigestionnecessary,anyway?Foodiscomposedofcarbohydrates,lipidsandproteins.Thesemacromoleculesmustbehydrolyzed(digested)beforecellscanabsorbthem.Chemicaldigestionoffoodbreaksdownmacromoleculesintotheirmonomers.

• Carbohydratesarebrokendownintosugars• Proteinsarebrokendownintoaminoacids• Fatsarebrokendownintofattyacidsandglycerol

Whyareenzymesneededfordigestion?Thehydrolysisofbiologicalmacromoleculesisaslowprocess.Enzymeslowertheactivationenergyofthesereactions,makingthemrunfaster.ExamplesofHumanDigestiveEnzymes:enzyme salivaryamylase pepsin phospholipaseA2source salivaryglands chiefcellsinstomach pancreassubstrate starch proteins phospholipidsproduct maltose polypeptide glycerol,phosphate&fattyacidsoptimumpH 7‐8 2‐3 8TheHumanDigestiveSystem

http://www.cudahychamber.com/images/digestive_system.gif


A.DeJong/TFSS2009

FunctionsofDigestiveOrgans

• Stomacho Primaryroleisstorageoffood(boluschyme)o Mechanical(physical)digestionoffoodaccomplishedbymusclecontractionand

actionofruggae;hydrochloricacidalsohasaneffecto Chemicaldigestionofproteinbegunbyactionofpepsino Carbohydrate(starch)digestioncontinues

• Smallintestineo Acidicchymeentersviathepyloricsphinctero Pancreaticjuice(bicarbonateion&enzymes)plusenzymessecretedbysmall

intestineneutralizechymeandcontinuechemicaldigestiono Aftercompletionofchemicaldigestion,foodmonomersareabsorbed

• Largeintestineo Primaryfunctionisreabsorptionofwater(enzymes,etc.addedtothelumenof

stomach&intestineinaqueoussolution)o Absorptionofmineralso Undigestedfoodmatter(feces)egested(defecated)viatherectum&anuso Regularintakeofdietaryfibre(cellulose,notdigested)assistsmovementoffeces

throughthelargeintestine(colon)

AbsorptionorAssimilation?Afterdigestion,foodmolecules(monosaccharides,aminoacids,glycerolandfattyacids)areabsorbedintothecirculatorysystem:monosaccharidesandaminoacidsareabsorbedintotheblood,whileglycerolandfattyacidsareabsorbedintothelymph.Thesenutrientsareassimilatedintothebodyoncetheyentercellsandareincorporatedintonew,largermoleculesagain.Thevillusisastructurefoundontheinnerwallofthesmallintestine.Villihelpincreasethesurfaceareaforabsorptionofnutrients:

Imagefromhttp://incostress1.files.wordpress.com/2007/10/villi.jpg


A.DeJong/TFSS2009

TheTransportSystemStructureoftheHumanHeart,andFlowofBlood:

Imagefromhttp://www.sirinet.net/~jgjohnso/heartstructure.html

**Note1:themitralvalveisalsocalledthebicuspidvalve.**Note2:theaorta&pulmonaryarterycontainsemi‐lunarvalves.ActionoftheHeartTheatria(sing.atrium)receivebloodfromtheveins.

• theleftatriumreceivesoxygenatedbloodfromthepulmonaryarteries• therightatriumreceivesdeoxygenatedbloodfromthevenacavae

Theventriclessendbloodoutoftheheartthrougharteries.• theleftventriclesendsoxygenatedbloodtobodytissuesviatheaorta• therightventriclesendsdeoxygenatedbloodtothelungsviathepulmonaryartery


A.DeJong/TFSS2009

Atrioventricular(AV)valvesconnecttheatriatotheventricles(thetricuspidontheright,andthebiscuspidontheleft),preventingbackflowofbloodintotheatriawhentheventriclescontract.Thesemi‐lunarvalvesintheaortaandpulmonarytrunkpreventbackflowofbloodintotheventriclesafterexitingtheheart.Theheartmuscleitselfreceivesoxygenandnutrientsviathecoronaryarteries.ControloftheHeartbeatHeartrate,measuredinbeatsperminute(b.p.m.)variesaccordingtofactorssuchasage,gender,fitness,activityandotherstimuli.Adultmale,atrest:75to80b.p.m.Adultfemale,atrest:85to90b.p.m.Nervousstimuli:fear,excitement,tensionPhysicalstimuli:exercise,temperatureChemicalstimuli:carbonmonoxide,oxygen,nicotine,caffeine,alcohol,hormonesUltimatecontroloftheheartrateisfromaregionofthebraincalledthemedullaoblongata.Twopairsofnervesrunfromthispartofthebraintotheheart.Onepairsendsstimulatorysignalstotheheart,andtheother,inhibitorysignals.Thesenervesconnectthebraintotheheart’scontrolcentre,thepacemaker.Theheartbeatitselfismyogenic–thismeansthatitisinitiatedwithintheheartmuscleitself,notthebrainoranotherpartofthebody.Thesinoatrial(SA)node(pacemaker)isaregionofspecializedhearttissuethatsendswavesofcontractionsthroughbothatria.Contractionoftheatriastimulatestheatrioventricular(AV)node,whichsendssignalsdownthebundleofHis,tothePurkinjefibres.Thiscausesventricularcontraction.Imagefromhttp://biology.about.com/library/organs/heart/blcardiacconduction.htm


A.DeJong/TFSS2009

Theventriclesmustcontractslightlyaftertheatria,toensureaproperflowofbloodthroughthesystem.Heartrateisapatternofaccelerationanddeceleration.Thevagusnervesendsinhibitorysignalstothepacemaker.Whenheartrateincreases,itisbecausetherearelessinhibitorysignalsfromthevagusnerve.Adrenalin,ahormoneproducedbytheadrenalgland,stimulatestheheartrateasapartofthebody’s“fightorflight”response.Ifthepacemakerfails,anartificialpacemakermaybeinsertedintotheheart.Thiswillhelpmaintainasteadyheartbeat,buttherecanbelittlevariationinheartrate.BloodVesselsTheflowofbloodthroughvesselsandtheheartisunidirectional.Thinkofarteries&veinsasone‐waystreets,justthesameaswiresincircuits.Arteriescarrybloodawayfromtheheart.Ingeneral,thisisoxygenatedbloodbeingbroughttothebody’stissues.Theexceptionisthepulmonaryartery,whichcarriesdeoxygenatedbloodtothelungs.RelatingStructuretoFunction:

• arterieshaveanarrowlumencomparedtotheirdiameter,whichhelpsmaintainhighbloodpressure&fastflowofblood

• arterieshaveamuscular,elasticwallwhichhelpspumpblood

• arterialwallshavecollagenfibreswhichhelppreventburstingduetohighbloodpressure

Arteriolesaresmallarteriesthateventuallyconnecttocapillaries.Veinscarrybloodtotheheart.Ingeneral,thisisdeoxygenatedbloodbeingbroughtbackfromthebody’stissues.Theexceptionisthepulmonaryvein,whichcarriesoxygenatedbloodfromthelungs.RelatingStructuretoFunction:

• veinshaveawidelumencomparedtotheirdiameter,whichallowsforslowbloodflowandlowbloodpressure

• veinshavethinnerwallswhichallowsurroundingskeletalmusclestopushbloodbacktowardstheheart

• veinscontainvalvestopreventback‐flowofblood,andpoolingofbloodinthelowerextremities

Venulesaresmallveinsthatcollectbloodfromcapillaries,andleadtolarger&largerveins.


A.DeJong/TFSS2009

Capillariesareextremelynarrowbloodvesselsthatconnectarteriolestovenules.Theyaretheonlysiteswithinthecirculatorysystemwherethereisamixofoxygenated&deoxygenatedblood.Exchangeofmaterials(gases,nutrients&wastes)occursinthecapillaries.RelatingStructuretoFunction:

• capillarywallsconsistofasinglelayerofflattenedcells,whichallowsfordiffusionofmaterialsbetweenthesurroundingtissuesandthebloodwithinthem

• capillarieshaveaveryfinediameter(oftensosmallthatredbloodcellsmustpassthrough“singlefile”),whichallowsthemtopenetratebetweencellsandtissues

• thecombinedsurfaceareaofcapillariesisgreat,whichincreasesthecapacityfordiffusionofmaterials

So,whydoweneedatransportsystem,anyway?Humansandmostothermulticellularorganismsaretoobigtosurvivewithoutatransportsystem.TheAmoeba,forexample,isaunicellularorganism,andusesdiffusionandcytoplasmicstreamingtotransportmaterialsthroughoutthecell.FunctionsoftheHumanTransportSystem:

1. TransportofNutrients:glucose,aminoacids,fattyacids&glycerol

2. TransportofRegulatoryChemicals:hormones,antibodies,enzymes

3. TransportofMetabolicWastes:urea(producedbytheliver),creatinine(producedbymuscles&releasedintoblood)

4. TransportofBloodProteins:albumins,globulins,fibrinogens

5. TransportofRespiratoryGases:oxygen,carbondioxide

6. MaintenanceofElectrolyte,pH,andosmoticbalancebetweentissuesandblood

7. ThermoregulationThreePathwaysforBlood

• Pulmonarysystemo Deoxygenatedbloodfromthebodyenterstherightatrium.o Itpassesthroughthetricuspidvalveintotherightventricle.o Fromhere,bloodgoesthroughthepulmonaryarterytothelungs.o Oxygenatedbloodreturnstotheheartviathepulmonaryvein.

• Coronarysystem(cardiacsystem)o Oxygenatedbloodenterstheleftatrium.o Itpassesthroughthebicuspidvalveintotheleftventricle.o Fromhere,bloodgoestotheaorta,thelargestarteryinourbody.o Thefirsttwoarteriesbranchingofftheaortaarethecoronaryarteries,which

supplytheheartmuscle.


A.DeJong/TFSS2009

• Systemic(Body)Systemo Bloodfromtheaortapassesintovariousmajorarteries,whichleadtoallpartsof

thebody.Bloodreturnstotheheartthroughveins&re‐entersthroughoneofthevenacavae.

Bloodiscomposedofthefollowing:

• Plasmao straw‐colouredliquido 90%watero contains:proteinsforclottingandinfections;dissolvednutrients;waste;

hormones;dissolvedgaseso 50%to60%ofbloodvolume

• RedBloodCellso a.k.a.erythrocyteso disk‐shaped;thinnerinthecentre(“biconcave”)o containhemoglobin

• WhiteBloodCellso a.k.a.leukocyteso <1%ofbloodo battleinfectionsandinvadersinourbodies

• Plateletso a.k.a.thrombocyteso responsibleforbloodclottingo formaplugatacut;alsoreleaseclottingfactorso producedasneeded(hormonalcontrol)

Imagefromhttp://content.answers.com/main/content/img/McGrawHill/Encyclopedia/images/CE087600FG0010.gif


A.DeJong/TFSS2009

Themainfunctionofbloodistocarryoxygenandcarbondioxidegases.Eachmoleculeofhemoglobinformsaweakbondwith4oxygenatoms.Thesebondsbreakinregionsoflowoxygen.Carbonmonoxidelovestotaketheplaceofoxygenonhemoglobin…hencethedangerofcarbonmonoxidepoisoning.GasExchangeVentilation,GasExchange&CellRespirationThesetermsareoftenallcalled“respiration”.Ventilation:muscularmovementrequiredinordertomaintainaconcentrationgradientsothatgaseousexchangecanoccur;breathingisventilationofthelungsGasExchange:themovementofoxygenfromtheairinthelungsintothebloodandcarbondioxideintheoppositedirectionCellRespiration:controlledreleaseofenergyintheformofATPfromorganiccompoundsincells


A.DeJong/TFSS2009

FunctionsoftheRespiratorySystem

1. Ventilation–providesoxygentothebloodstreamandremovescarbondioxide.2. Vocalization–productionofsounds;speech.3. Assistinginabdominalcompressionduring

a. Urinationb. Defecationc. Childbirthd. Liftingheavyobjects

Theabdominalmusclesbecomemoreeffectivewhenairisheldinthelungs&glottisisclosed.

Breathein…breatheout…VentilationofthelungsVentilationofthelungsisaccomplishedbybreathingin&out.Thisisnecessarybecausethelungsneedaconstantsupplyoffreshairtomaintaintheconcentrationgradientbetweenthealveoliandtheircapillaries.Sincethereisonlyoneconnectionbetweenthelungsandtheatmosphere,staleairmustbeexhaledbeforefreshairisinhaled.Breathein…Inspirationoccursbecausetheintercostalmuscles(betweentheribs)contract,movingtheribcageupward&outward;atthesametime,thediaphragmcontracts,movingitdownward.Theseactionscombinetoincreasethevolumeofthechestcavity.Whenthevolumeofthechestcavityincreases,theairpressureinsidethelungsdecreases,becominglessthantheatmosphericairpressure;thisbringsairintothelungs.Breatheout…Expirationoccursbecausetheintercostalmusclesanddiaphragmrelax,andtheyreturntotheiroriginalposition.Thisdecreasesthevolumeofthechestcavity.Whenthevolumeofthechestcavitydecreases,theairpressureinsidethelungsincreases,becominggreaterthantheatmosphericairpressure;thispushesairoutofthelungs.Imagefromhttp://www.fda.gov/fdac/graphics/1999graphics/breathing.gif


A.DeJong/TFSS2009

Howmuchairarewetalkingabout,here?Name Volume

(cm3)Description

TidalVolume(TV) 500 volumemovedinoroutofthelungsduringquietbreathing

InspiratoryReserve(IRV)

3000 volumethatcanbeinhaledduringforcedvolumebreathinginadditiontotidalvolume

ExpiratoryReserve(ERV)

1100 volumethatcanbeexhaledduringforcedvolumebreathinginadditiontotidalvolume

ResidualVolume(RV) 1200 volumethatremainsinthelungsatalltimesInspiratoryCapacity(IC)

3500 maximumvolumeofairthatcanbeinhaledfollowingexhalationoftidalvolumeIC=TV+IRV

FunctionalResidualCapacity(FRC)

2300 volumeofairthatremainsinthelungsfollowingexhalationoftidalvolumeFRC=ERV+RV

VitalCapacity(VC) 4600 maximumvolumeofairthatcanbeexhaledaftertakingthedeepestbreathpossibleVC=TV+IRV+ERV

TotalLungCapacity(TLC)

5800 totalvolumeofairthatthelungscanholdTLC+VC+RV

Non‐RespiratoryAirMovementsWhat? How? Why?coughing deepbreathistaken,glottisisclosed,andairis

forcedagainsttheclosure;suddenlytheglottisisopenedandablastofairpassesupward

clearslowerrespiratorypassages

sneezing sameascoughing,exceptairmovingupwardisdirectedintothenasalcavitybydepressingtheuvula

clearsupperrespiratorypassages

laughing deepbreathisreleasedinaseriesofshortexpirations

expressesemotionalhappiness

crying sameaslaughing expressesemotionalsadnesshiccupping diaphragmcontractsspasmodicallywhileglottis

isclosednousefulfunction

yawning deepbreathistaken ventilatesalargerproportionofthealveoliandaidsoxygenationoftheblood

speech airisforcedthroughthelarynx,causingvocalcordstovibrate

vocalcommunication;wordsareformedbylips,tongueandsoftpalate


A.DeJong/TFSS2009

IntroductiontoGasExchange

• Gasexchange(=respiration)istheuptakeofoxygenandthereleaseofcarbondioxideo O2isrequiredforcellularmetabolismo CO2isaby‐productofmetabolism

• O2isextractedfromairorwatero Diffusionacrossexternalsurfaceoverlayingacapillarybed.o CO2transportedacrosssamesurface(netflowinoppositedirection).

• Gasexchangeacrosslungs(=pulmonary)ornon‐pulmonary(i.e.inthetissues)routes.

Imagefromhttp://distance.stcc.edu/AandP/AP/imagesAP2/respiration/alvexch.jpg

Imagefromhttp://faculty.uca.edu/~johnc/CapillaryExchange.gif


A.DeJong/TFSS2009

RequirementsforGasExchangeFourthingsareneededforgasexchange:

1. aconcentrationgradient(fordiffusion)2. amoistmembrane(O2enterscellsdissolvedinwater)3. adequatesurfacearea(providedby1000’sofalveoli…ourlungsarenotemptyballoons)4. aninternaltransportsystem(networkofcapillariessurroundseachalveolus)

Howalveolimeettheneedsforgasexchange:

• largetotalsurfacearea• thinwallsconsistingofasinglelayerofflattenedcells• moistlining• densenetworkofcapillaries

PhasesofHumanRespiration

1. Breathing(ventilation)–movementofairinto&outofthelungs2. ExternalRespiration–exchangeofgasesbetweenair&blood(see,alveoliarereally

outsidethebody!)3. Circulation–movementofdissolvedgasestoandfromthecellsbyblood4. InternalRespiration–exchangeofgasesbetweenbloodandcells/tissues

ControlofBreathingBreathingisaninvoluntaryprocessthatcanbecontrolledvoluntarily.Breathingiscontrolledbytherespiratorycentreinthebrain(partofthemedullaoblongata),andbychemoreceptorsinlargearteries(e.g.aorta)thatmonitorlevelsofO2andCO2.CompositionofAtmospheric&ExhaledAir:Component AtmosphericAir(%) ExhaledAir(%)N2(plusinertgases) 78.62 74.9O2 20.85 15.3CO2 0.03 3.6H2O 0.5 6.2 100% 100%Notethatthelungsonlytakeupafractionoftheoxygeninhaled.ThisisexploitedwhenweperformArtificialRespirationduringCPR.Theoxygenlevelofexhaledairissufficienttosupplyoxygentothecellsofsomeonewhoisnotbreathing.

IB Biology Notes for Digestion, Circulation & Respirationtfssbio.pbworks.com/f/Dig Circ Resp...

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