Topic 6: Human Physiology

Topic6:HumanPhysiology6.2TheBloodSystem

D.4TheHeart

EssentialQuestions:6.2Thebloodsystemcontinuouslytransportssubstancesto

cellsandsimultaneouslycollectswasteproducts.D.3Thechemicalcompositionofbloodisregulatedbytheliver.D.4Internalandexternalfactorsinfluencetheheartfunction.

OurCirculatorySystem

•  Systemcomprisedofaheart,bloodvessels,&lymphglands

•  Worktogethertosupplythebodytissueswithnourishmentandcollectwastematerials.

Arteries,Veins,Capillaries

CrossSectionofanArteryandaVein

OrganizationofArteries,Arterioles,Capillaries,VenulesandVeins

Arteries•  Haveathickouterlayer

oflongitudinalcollagenandelastinfibers

•  Toavoidleaksandbulges

•  Thickwalled•  Towithstandhighpressure

•  NarrowLumen•  Maintainshighpressureinsidearteries

•  Circularelasticfibresandmusclefibres

(elastic-liketissues)•  Towithstandthepressurefromtheheart’sbeating•  Tohelppumpbloodaftereachcontractionofheart

•  Porous•  Allowsplasmatoleakoutandformtissuefluid•  Phagocytescanalsopassthroughpores

•  Smalldiameter(narrowlumen)•  Bloodcellspassthroughinsinglefile•  Allowsformanycapillariestofitintoasmallspace

•  Semi-permeablemembrane•  allowsnutrients,oxygen,andwatertodiffusefrombloodintothetissues

Capillaries

•  Connectarteriestoveins

•  Wallisonecellthick•  Thusshortdistancefordiffusiontooccur

•  Thin-walled

Veins•  Thinouterlayeroflongitudinalcollagenandelastinfibres

•  Becausepressureislow

•  Thin,collapsiblewalls•  Fewcircularelasticfibresandmusclefibresasblooddoesnotflowinpulses•  Nearbymusclescanhelppushbloodbacktowardheart

•  WideLumen•  Accommodatetheslowflowingblood

•  Valves•  Preventbloodfromreversingflow

CrossSectionofBloodVessels

HistologyofArteries&Veins

Source:legacy.owensboro.kctcs.edu

ComparisonofArteries,VeinsandCapillaries

FromPearsonHLBiology

Atherosclerosis

•  Developedbydepositsofplaque(cholesterol,lipids,calcium,celldebris)accumulateatatearintheinnerlayeroftheartery

•  Hardens,andoccludesthelumen

•  Bloodflowtotissuesdecreasesandaclotcanbecomelodgedandcompletelyobstructcirculation

•  Canleadtoheartattack

TheHeart

TheHeart-Valves

Differentnamesforthevalvesoftheheart:

FromPearsonHLBiology

MyogenicControloftheHeart

•  Heartismadeupofcardiacmuscle–  CardiacmuscleisMYOGENIC-meaningitnaturallycontractsandrelaxes(originatesfromtheheartitself)•  Itreceivesnocontrolfromanervetomakeitcontract•  ItsAUTOMATIC!

•  Somecontrolbyautonomicnervoussystem•  RespondstochangesinbodyAUTOMATICALLY•  Example:increasedbodyactivity=running

•  Electricalimpulsescausesregularcontractionsoftheatriafirst,thentheventricles=heartbeat

BloodComposition

•  Transport(Highway)aroundbody•  nutrients,•  Gases(eg.oxygenandcarbondioxide)•  Hormones(Communication,Homeostasis)•  Antibodies,leucocytes(WBC)•  urea•  Heat

BloodComposition

•  Plasma•  Fluid•  carriesallothercomponentsofblood,nutrientsandwastes

•  Erythrocytes(RBC’s)•  Producedinbonemarrow (oflargebones)•  Transportsoxygenandcarbondioxide

BloodComposition•  LymphocytesandPhagocytes(WBC’s)

•  Producedinbonemarrow•  Belongstoimmunesystem

•  Platelets•  Cellfragmentsthataidinbloodclotting

Adropofbloodcontainsapproximately:-  5millionRBC-  10,000WBC-  250,000platelets

Topic6:HumanPhysiology6.2TheBloodSystem

D.4TheHeart

EssentialQuestions:6.2Thebloodsystemcontinuouslytransportssubstancesto

cellsandsimultaneouslycollectswasteproducts..

D.4Internalandexternalfactorsinfluencetheheartfunction.

OurCirculatorysystemisadoublecirculatorysystem.Ithastwoparts:

the left side of the system

deals with oxygenated

blood.

the right side of the system

deals with deoxygenated

blood.

Lungs

Bodycells

TypesofCirculation

1)  Pulmonary-  movementofbloodàheart-lungs–heart

2)  Systemic-  Movementofbloodàheart–body–heart

3)  Coronary -bloodvesselsthatsupplythemuscleoftheheartwith oxygen/nutrientsandremovewasteproducts

Red portion of heart and red blood vessels carry oxygen-rich blood.

Blue portion of heart and blue blood vessels carry oxygen-poor blood.

PulmonaryCirculation

CardiacCycle-  Seriesofeventsreferredtoasoneheartbeat-  Frequencyofthecardiaccycleisyourheartrate(measuredinbeatsperminute)

-  80beatsmin-1=80cardiaccycleseveryminute

Systole(sis-tol-ee)Diastole(di-as-tol-ee)

Contractionoftheheart RelaxationoftheheartNote:Bothatriacontractatthesametime,andboth

ventriclescontractatthesametime,justamomentlaterthen

theatria

Diastole(=60-80mmHgadults)•  Both Chambers are at rest (no

contracting)

•  Minimum pressure in the arteries

•  Atrial pressure is slightly higher then ventricular pressure keeping the left atrioventricular valve open

•  Blood moves passively from atrium into ventricle

•  The valve of the aorta is kept closed = no backflow

Systole(=90-120mmHgadults)•  Contraction

•  Maximum pressure on the arteries

•  Atria in Systole first –generates a little pressure to move any remaining blood into the ventricle

•  Ventricles in systole – pressure inside is greater then the atrium so the valves close to prevent backflow (=lub)

•  Ventricular pressure builds up until pressure becomes greater in the ventricle then the aorta causing the semilunar valve to open. Blood is forced into aorta

•  Ventricle finishes contraction and semilunar valve closes (=dub)

BloodPressure•  Anadultisconsideredsufferingfromhypotensionifthediastolicreadingis<60mmHgandsystolicreadingis<90mmHg

•  Prehypertensionifthediastolicreadingis81–89mmHgandsystolicreadingis121–139mmHg

•  Stage1Hypertensionifthediastolicreadingis90–99mmHgandsystolicreadingis140–159mmHg

•  Stage2Hypertensionifthediastolicreadingis100mmHgandsystolicreadingis160mmHg

OcclusioninCoronaryArtery

•  Blockageofoneofthethreemajorcoronaryarteriesortheirbranches

•  Heart(oraportionofit)becomesdeprivedofoxygen=myocardialinfarction

http://nursingcrib.com/peir.path.uab.edu

CoronaryCirculation

FromA.D.A.M

•  Vesselsdeliveroxygenrichbloodtotheheart

•  Highlyaffectedbyatherosclerosiswhichcancauseanginaorheartattack

•  CardiaccycleinitiatedbysmallpatchofmusclecalledtheSANode(sino-atrialnode)orPACEMAKER

•  Thisnodesetstherhythmforallcardiacmuscle(notthebrain)•  Foraheartrateat72beats/min,theSANgeneratesanactionpotentialevery0.8seconds(ataregularfrequency)–  Thepacemakercellshaveabuilt-inrhythmthatisfasterthanallotherheartcells

MyogenicControloftheHeart

•  SAnodesendsoutanactionpotential(AP)andspreadsoutthroughtheatrialeadingtosystole(contraction)

•  SAnode’sAPreachestheatrioventricularnode(AVnode)locatedinthelowerwallofrightatrium/septum

•  AVnodesendsoutanewAPthatspreadstobothventriclesaftera0.1seconddelay

•  PurkinjefibreshelpspreadtheAPthroughthethickwallsoftheventriclescausingventricularsystole

MyogenicControloftheHeart

Electrocardiograms(ECG’s)

•  Usedtomeasureheartrate

•  Eacheventinthecardiaccyclehasadistinctivewaveform

•  Everyrepeatingpatternisarepresentationofonecardiaccycle

HowtoReadanECG

•  Pwave–  showsvoltageofAPfromSA

node=atrialsystole

•  Qpoint–  AVnodesendsitsimpulse

•  QRScomplex–  APfromtheAVnodespreads

downPurkinjefibreswithinventricles(=ventricularsystole)

•  Twave–  repolarizationofAVnode

(anotherheartbeatcannotoccuruntilrepolarizationiscomplete)

Electrocardiograms(ECG’s)