Mammalian Circulatory system

Mammalian Circulatory System, in comparison with aves, reptiles, and fish.
Animal Physiology

1. Topic: Mammalian Circulatory System
Class Reporter: Elino, M. M. H.
Class Instructor: Geonyzl Lepiten-Alviola, MSBio

2. REPORT OUTLINE:
I-Brief Introduction of the Mammalian Heart
II-Pumps: Mechanical Events of the Mammalian Cardiac Cycle
III-Pumps: Cardiac Output and Its Control
IV-Pumps: Nourishing the Vertebrate Heart Muscle (Coronary Circulation)
VI-Circulatory Pathways and Vessels
VII-Vessels: Flow Regulation and Hemodynamics
VIII-Pathways: Open Circulation
IX-Pathways: Closed Circulation
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.

3. The Mammalian Heart has four chambers:
Right Atrium, Left Atrium, Right Ventricle, Left Ventricle
1) The Right Atrium and Left Atrium are reservoirs for blood (to be sent
to Right Ventricle and Left Ventricle)
2) The Right Ventricle and Left Ventricle are the main pumping
chambers of the heart
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Brief Introduction on Mammalian Heart and Circulation

4. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Brief Introduction on Mammalian Heart and Circulation
Right Atrium Left Atrium
Right Ventricle
Left Ventricle
The Mammalian Heart has four chambers:

5. The Mammalian Heart has four valves:
two Atrioventricular Valves (AV) and two Semilunar Valves (SV)
1) Tricuspid Valve –an AV valve between Right Atrium -Right Ventricle
2) Bicuspid Valve –an AV valve, also called “Mitral Valve” between Left
Atrium and Left Ventricle
3) Pulmonary Valve –a SV valve between the Right Ventricle and
Pulmonary artery
4) Aortic Valve –a SV valve between Left Ventricle and Aorta
Valves act as one-way doors to keep blood moving forward
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Brief Introduction on Mammalian Heart and Circulation

6. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Brief Introduction on Mammalian Heart and Circulation
Pulmonary Valve Aortic Valve
Tricuspid Valve
Bicuspid Valve
The Mammalian Heart has four chambers:

7. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Brief Introduction on Mammalian Heart and Circulation
Sinoatrial Node
Aorta
Atrioventricular Node
Pulmonary Artery
Other Parts
Superior Vena Cava
Inferior Vena Cava
Pulmonary Vein
Bundle of His
Septum
Purkinjie Fibers
Myocardium

8. The Circulation (Brief Diagram):
Deoxygenated bloodfrom the body returns to the heart via:
Superior and Inferior Vena Cava Right Atrium Tricuspid Valve
Right Ventricle Pulmonary Valve Pulmonary Artery Lungs
(the blood now comes oxygenated)
Oxygenated bloodfrom the lungs returns to the heart via:
Pulmonary Vein Left Atrium Bicuspid Valve Left Ventricle
Aortic Valve Aorta Body (the blood now comes deoxygenated)
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Brief Introduction on Mammalian Heart and Circulation

9. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Brief Introduction on Mammalian Heart and Circulation

10. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Brief Introduction on Mammalian Heart and Circulation

11. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Brief Introduction on Mammalian Heart and Circulation

12. The cardiac cycle consists of alternate periods of
Systole–the contraction and emptying
Diastole–relaxation and filling
In vertebrates, the atria and ventricles go through separate cycles of
systole and diastole.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

13. Hearts alternately contract to empty and relax to fill.
Contraction–occursasaresultofthespreadofexcitation
acrosstheheart;depolarizationofthemusclesoftheheartfollowsthe
contraction.
Relaxation–follows the subsequent repolarization of the
cardiac musculature.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

14. ECG –Electrocardiogram
Theelectricalcurrentsgeneratedbycardiacmuscleduring
polarizationandrepolarizationspreadintotissuessurroundingthe
heartandareconductedthroughbodyfluids.
Asmallportionofthiselectricalactivityreachesthebody
surface,whereitcanbedetectedusingrecordingelectrodesonskin.
Therecordproduceisanelectrocardiogram.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

15. Electrocardiogram
-itisarecordingofthatportionoftheelectricalactivityinducedbythe
bodyfluidsbythecardiacimpulsethatreachesthesurfaceofthebody.
-isacomplexrecordingrepresentingtheover-allspreadofactivity
throughouttheheartduringdepolarizationandrepolarization.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

16. Electrocardiogram
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

17. Electrocardiogram
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle
P wave represents atrial
depolarization
QRS complex represents ventricular
depolarization.
T wave represents ventricular
repolarization

18. Depolarization–achangeinacell'smembrane
potential,makingitmorepositive,orlessnegative.
Repolarization–reestablishmentofpolarity,especiallythe
returnofcellmembranepotentialtorestingpotential
Action Potential –is a short-lasting event in which the electrical
membrane potential of a cell rapidly rises and fall, following a
consistent trajectory; whenever there’s large depolarization among
cells
Resting Potential –resting event, opposite to action
potential, comes after action potential, whenever there’s a large
repolarization among cells
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

19. Excitation/ActivationofheartbySino-AtrialNode(especializedauto-
rhythmiccells).
(animation / presentation)
File name: conduction_ct.swf
Download my file at:
http://www.4shared.com/rar/13zOoh6I/animal_physio_reports_ppt.html
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

20. The Full Cardiac Cycle:
1) Early Ventricular Diastole
2) Late Ventricular Diastole
3) End of Ventricular Diastole
4) Ventricular Excitation and Onset of Ventricular Systole
5) Isovolumetric Ventricular Contraction
6) Ventricular Ejection
7)End of Ventricular Systole
8) Ventricular Repolarization and Onset of Ventricular Diastole
9) Isovolumetric Ventricular Relaxation
10) Ventricular Filling
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

21. 1
st
: Early Ventricular Diastole
Duringearlyventriculardiastole,theatriumisstillalsoin
diastole.ThisstagecorrespondstotheTPinterval(ontheECG)–the
restingstage.
TheAVvalveisopen.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

22. 2
nd
: Late Ventricular Diastole
SA node reaches threshold and fires.
Impulse spreads through out the atria and is recorded on the
ECG as P wave.
Atrial depolarization brings about atrial contraction which
squeezes more blood into the ventricle, causing a rise in the atrial
pressure curve.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

23. 3
rd
: End Ventricular Diastole
VentricularDiastoleendsattheonsetofventricular
contraction.Bythistime,atrialcontractionandventricularfillingare
completed.
Thevolumeofthebloodintheventricleattheendofdiastole
isknownas“end-diastolicvolume”(EDV),whichaveragesabout
135mLinhumans.
Nomorebloodisaddedtotheventricleduringthiscycle.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

24. 4
th
: Ventricular Excitation and Onset of Ventricular Systole
Followingatrialexcitation,theimpulsepassesthroughtheAV
nodeandspecializedconductionsystemtoexcitetheventricle.
QRScomplexrepresentsthisventricularexcitationwhich
induceventricularcontraction.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

25. 5
th
: Isovolumetric Ventricular Contraction
AfterventricularpressureexceedsatrialpressureandAVvalve
hasclosed,theventricularpressuremustcontinuetoincreasebeforeit
canopentheaorticvalve.
BetweenclosureoftheAVvalveandopeningofAortic
valve,thereisabriefperiodoftimewhentheventricleremainsa
closedchamber.Duringthistime,nobloodcanenterorleavethe
ventricles.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

26. 6
th
: Ventricular Ejection
Itiswhenventricularpressureexceedsaorticpressure.The
aorticvalveisforcedopenandejectionofthebloodbegins.
Theventricularvolumedecreasessubstantiallyasblood
rapidlypumpedout.
Ventricular systole includes both the period of isovolumetric
contraction and the ventricular ejection phase.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

27. 7
th
: End of Ventricular Systole
AfterventricularpressureexceedsatrialpressureandAVvalve
hasclosed,theventricularpressuremustcontinuetoincreasebeforeit
canopentheaorticvalve.
BetweenclosureoftheAVvalveandopeningofAortic
valve,thereisabriefperiodoftimewhentheventricleremainsa
closedchamber.Duringthistime,nobloodcanenterorleavethe
ventricles.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

28. 8
th
: Ventricular Repolarization and Onset of Ventricular Diastole
ItissignifiedbyTwave,occurringattheendofventricular
systole.Astheventriclesstartstorelaxonrepolarization,ventricular
pressurefallsbelowaorticpressureandtheaorticvalvescloses.
Closureoftheaorticvalveproducesadisturbanceasnotchon
theaorticpressurecurveknownasthe“discroticnotch”.
Nomorebloodleavestheventricleduringthis
cycle/phase,becausetheaorticvalvehasclosed.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

29. 9
th
: Isovolumetric Ventricular Relaxation
Whentheaorticvalvecloses,theAVvalveisnotyet
open,becauseventricularpressurestillexceedsatrialpressure,sono
bloodcanentertheventriclefromtheatrium.Therefore,allvalvesare
onceagainclosedforabriefperiodoftime.
Themusclefiberlengthandchambervolumeremainconstant.
Nobloodmovesastheventriclecontinuestorelax;pressuresteadily
falls.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

30. 10
th
: Ventricular Filling
Whentheventricularpressurefallsbelowtheatrial
pressure,theAVvalveopensandventricularfillingoccursonceagain.
Ventricular Diastole includes both the period of isovolumetric
ventricular relaxation and the ventricular filling phase.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

31. (PointstoPonder)
AtrialrepolarizationandVentriculardepolarizationoccur
simultaneously,sotheatriaareindiastolethroughoutventricular
systole.
Bloodcontinuestoflowfromthepulmonaryveinsintotheleftatrium.
Asthisincomingbloodpoolsintheatrium,atrialpressurerises
continuously.
WhentheAVValveopensattheendofventricularsystole,the
bloodthataccumulatedintheatriumduringventricularsystolepours
rapidlyintheventricle.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

32. (PointstoPonder)
Ventricularfillingthusoccursrapidlyatfirstbecauseoftheincreased
atrialpressureresultingfromtheaccumulationofbloodintheatria.
Thenventricularfillingslowsdownandatrialpressurestartstofall.
Duringtheperiodofventricularfilling,thebloodcontinuestoflow
fromthepulmonaryveinsintotheleftatriumandthroughtheopen
AVvalveintotheleftventricle.
Duringlateventriculardiastole,whenventricularfillingisproceeding
slowly,theSAnodefiresagainandthecardiaccyclestartsover.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Mechanical Events of the Mammalian Cardiac Cycle

33. Cardiac Output
Itisthevolumeofbloodperminutepumpedbyahearttothe
body,andisthemostimportantphysiologicalparameterofacirculatory
pump.
Itdependsontheheartrateandthestrokevolume.Thus,the
keyformulais:
Cardiac Output = Heart Rate x Stroke Volume
(volume per minute) (beats per minute) (volume per pumped
per beat of stroke)
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

34. Cardiac Output depends on the heart rate and the stroke volume.
Heartratesvarytremendouslywithactivitystateofanindividualand
acrosstheanimalkingdom.
Largeranimalstendtohaveslowerheartrates.Ex:6beats/minfor
whalesand300beats/mininarat.
Duringanyperiodoftime,thevolumeofbloodflowingthrough
pulmonarycirculationisequivalenttothevolumeflowingthrough
systemiccirculation.
Cardiacoutputfromeachventricleisnormallyidentical,minor
variationsmayoccur.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

35. Cardiac Output depends on the heart rate and the stroke volume.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control
CARDIAC OUTPUT = Heart Rate x Stroke Volume
Horse 13, 500mL/min = 30 beats/min x450 mL/beat
Human 4, 900 mL/min = 70 beats/min x 70 mL/beat
Pigeon 195.5 mL/min = 115 beats/min x 1.7 mL/beat
Trout 17.4 mL/min = 37.8 beats/min x 0.46 mL/beat

36. Cardiac Output depends on the heart rate and the stroke volume.
CardiacOutputchangeswithdevelopment.Inyoungbroiler
chicks,strokevolumealmostdoublesinatwo-weekperiod:
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control
CARDIAC OUTPUT = Heart Rate x Stroke Volume
4 weeks old 253mL/min = 362 beats/min x0.70 mL/beat
6weeks old 434 mL/min = 328 beats/min x 1.33 mL/beat

37. Cardiac Output depends on the heart rate and the stroke volume.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control
Thorough Bred Horse300,000mL/min
Human(untrained)25,000mL/min
Human (athlete)40,000mL/min
Pigeon1,072mL/min
Trout53mL/min
CardiacOutputalso
changeswithactivity,
oftenbylargeamounts.
Thefollowingare
somevaluesthathave
beenmeasuredathigh
activitylevels(running,
flying,swimming)

38. Heart rate is determined primarily by antagonistic regulationof
autonomic influences on the SA node.
Thevertebrateheartisinnervatedbybothdivisionofthe
ANS,whichisthesympatheticandparasympatheticNervous
System,whichcanmodifytherate(aswellasstrength)of
contraction,eventhoughnervousstimulationisnotrequiredtoinitiate
contraction.
Theparasympatheticnervetothemammalianheart,thevagus
nerve,primarilysuppliestheatriumespeciallytheSAandAVnodes.
Parasympatheticinnervationoftheventriclesissparse.
Thecardiacsympatheticnervesalsosupplytheatria,including
SAandAVnodes,andrichlyinnervatestheventriclesaswell.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

39. Heart rate is determined primarily by antagonistic regulationof
autonomic influences on the SA node.
Bothparasympatheticandsympatheticnervoussystemaffect
theheartbyalteringtheactivityofthecyclicAMP(secondmessenger
systemintheinnervatedcells.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

40. Heart rate is determined primarily by antagonistic regulationof
autonomic influences on the SA node.
Bothparasympatheticandsympatheticaffecttheheartthrough
thereleaseof:
1)Acetylcholine(Ach)–releasedfromthevagusnervebindsto
muscarinicreceptorsthatarecoupledtoaninhibitoryGprotein,which
reducesthecyclicAMPpathway.cAMPinturnincreasesthe
permeabilityoftheSAnodetoK+byslowingtheclosureofEAGK+
channel.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

41. Heart rate is determined primarily by antagonistic regulationof
autonomic influences on the SA node.
Bothparasympatheticandsympatheticaffecttheheartthrough
thereleaseof:
2)Norepinephrine(NE)–sympatheticneurotransmitterbindswithaB-
adrenergicreceptorthatiscoupledtoastimulatoryGprotein,which
acceleratescAMPpathway.Inturn,cAMPappearstodecreaseK+
permeabilitybyacceleratinginactivationofEAGchannels.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

42. Heart rate is determined primarily by antagonistic regulationof
autonomic influences on the SA node.
Bothparasympatheticandsympatheticaffecttheheartthrough
thereleaseof:
3)AchandNEthatbothaffectsCa++conduction.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

43. Effect of Parasympathetic Stimulation on the Mammalian Heart
Parasympathetic stimulation reduces cardiac output through
these effects:
1)It decreases heart rate.
2)It decreases excitability of the AV node.
3)It shortens the action potential of the atrial contractile cells.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

44. Effect of Sympathetic Stimulation on the Mammalian Heart
Sympathetic stimulation increases cardiac output through
these effects:
1)It increases heart rate through its effect on pacemaker tissue.
2)It reduces AV nodal delay at the node by increasing conduction
velocity.
3)It speeds up the spread of the action potential throughout the
specialized conduction pathway.
4)It increases contractile strength of the atrial and ventricular
contractile cells.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

45. Control of the Heart Rate
Thus,astypicaloftheANS,parasympatheticandsympathetic
effectsonheartrateareexampleofantagonisticrelation.Atanygiven
moment,theheartrateisdeterminedlargelybytheexistingbalance
betweentheinhibitoryeffectsofvagusnerveandthestimulatory
effectsofthecardiacsympatheticnerves.
Therelativelevelofactivityinthesetwobranchesinturnis
primarilycoordinatedbythecardiovascularcontrolcenterlocatedat
thebrainstem.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

46. ControloftheHeartRate
Althoughautonomicinnervationistheprimarymeansbywhich
heartrateisregulated,otherfactorsaffectitaswell.Themost
importantisepinephrine,ahormonethatissecretedintotheblood
fromtheadrenalmedullaonsympatheticstimulationandtheactsina
mannersimilartonorepinephrinetoincreasetheheartrate.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

47. Stroke Volume is determined by the extent of venous return and by
sympathetic activity.
The other component that determines the cardiac output is
stroke volume, the amount of blood pumped out by each ventricle
during each beat. Two types of controls influence stroke volume:
1)Intrinsic Control –related to the extent of venous return
2)Extrinsic Control –related to the extent of sympathetic stimulation
of the heart.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

48. Increased end-diastolic volume results in increased stroke volume
Asmorebloodisreturnedtothevertebrateheart,theheart
pumpsoutmoreblood,buttheheartdoesnotejectallthebloodit
contains.Thedirectcorrelationbetweenend-diastolicvolumeand
strokevolumeconstitutestheintrinsiccontrolofstokevolume,which
referstotheheart’sinherentabilitytovarythestrokevolume.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

49. Frank-Starling Law of the Heart
states that:
“ Heart normally pumps all the blood returned to it”
This effect is not unique to invertebrates; for example, mollusk hearts
also respond in this way to increased filling (they also beat faster in
response)
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

50. Frank-Starling Law of the Heart
The built-in relationship matching stroke volume with venous
return has two important advantages:
1)Itisforequalizationofoutputbetweentherightandleftsidesofthe
avianandmammalianhearts,sothatthebloodpumpedoutbythe
heartisequallydistributedbetweenpulmonaryandsystemic
circulation.
2)Whenlargercardiacoutputisneededinanyvertebrate,venous
returnisincreasedthroughactionofthesympatheticnervous
system.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

51. The contractility of the heart and venous return are increased by
sympathetic stimulation.
Inadditiontointrinsiccontrol,strokevolumeisalsosubjectto
extrinsiccontrolbyfactorsoriginatingoutsidetheheart,themost
importantofwhichareactionsofthecardiacsympatheticnervesand
epinephrine.Sympatheticstimulationandepinephrineactintotwo
ways:
1)Theheartcontractsmoreforcefullyandsqueezesoutagreater
percentageoftheblooditcontainsonsympatheticstimulation.
2)Sympatheticstimulationincreasesstrokevolumealsoby
enhancingvenousreturn.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

52. The contractility of the heart and venous return are increased by
sympathetic stimulation.
Thestrengthof cardiacmuscle contractionand
accordingly,thestrokevolumecanthusbegradedby
1)Varyingtheinitiallengthofthemusclefibers,whichturndepends
onthedegreeofventricularfillingbeforecontractionand;
2)Varyingtheextentofsympatheticstimulation(extrinsiccontrol).
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Cardiac Output and Its Control

53. Theheartreceivesmostofitsownbloodsupplythroughthecoronary
circulation.
Coronarycirculationisthecirculationofbloodintheblood
vesselsoftheheartmuscle(themyocardium).Thevesselsthatdeliver
oxygen-richbloodtothemyocardiumareknownascoronaryarteries.
Thevesselsthatremovethedeoxygenatedbloodfromtheheart
muscleareknownascardiacveins.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Nourishing the Vertebrate Heart Muscle

54. Theheartreceivesmostofitsownbloodsupplythroughthecoronary
circulation.
Althoughthebloodpassesthoughtheheart,theheartmuscle
cannotextractO
2ornutrientsfromthebloodwithinitschamber,inpart
becausethewallsaretoothicktopermitdiffusionofO
2andother
suppliesfromthebloodinthechambertoallthecardiaccells.
Therefore,likeothertissuesofthebody,heartmusclemust
receivebloodthroughbloodvessels,specificallybymeansofthe
coronarycirculation(whichfirstevolvedinfishes).Thecoronary
arteriesbranchinfishesfromthebranchialarteriesleavingthe
gills,andinmammalsfromtheaortajustbeyondtheaorticvalve.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Nourishing the Vertebrate Heart Muscle

55. CoronaryCirculation
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Nourishing the Vertebrate Heart Muscle

56. CoronaryCirculation
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Nourishing the Vertebrate Heart Muscle

57. CoronaryCirculation
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Nourishing the Vertebrate Heart Muscle

58. CoronaryCirculation
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Nourishing the Vertebrate Heart Muscle

59. CoronaryCirculation
Duringlocomotoryactivity,therateofcoronarybloodflowincreases
several-foldaboveitsrestingstate.Increaseddeliveryofbloodtothe
cardiaccellsisaccomplishedprimarilybyvasodilation,or
enlargement,ofthecoronaryvessels,whichallowsmorebloodto
flowthroughthem.
Coronarybloodflowisadjustedprimarilyinresponsetochangesin
theheart’sO
2requirements.
Themajorlinkthatcoordinatescoronarybloodflowwithmyocardial
O
2needsisadenosine(whichisformedfromATP).
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Nourishing the Vertebrate Heart Muscle

60. CoronaryCirculation
Increasedformationandreleaseofadenosinefromcardiaccellsoccur:
1)WhenthereiscardiacO
2deficitor
2)Whencardiacactivityisincreasedandtheheartaccordingly
requiresmoreO
2forATPproduction.
Theheartprimarilyusesfreefattyacids,glucose,lactateasfuel
sources.Note:dependingontheiravailabilityanditcanshiftmetabolic
pathwaystousewhatevernutrientisavailable.
Theprimarydangerofinsufficientcoronarybloodflowisnotfuel
shortagebutO
2deficiency.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Nourishing the Vertebrate Heart Muscle

61. CoronaryCirculation
Reduced O
2in cardiac adenosine release
vasodilation of coronary vessels
increased blood flow and O
2delivery to myocytes
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pumps: Nourishing the Vertebrate Heart Muscle

62. Circulatoryfluidstransportmaterialsinaparallelmanner,especiallyin
closedsystems.
Mostanimalshaveeitheropen(hemolymph)oraclosed
(blood)system.
Bloodmovesthroughclosedvessels.
Hemolymphmovesmorerandomlythroughopenspaces“lacunae”
amongorgans.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Circulatory Pathways and Vessels

63. Circulatoryfluidstransportmaterialsinaparallelmanner,especiallyin
closedsystems.
Therearetwoimportantdesignfeaturesinclosed(andoften
inopensystem)
1)Closedsystemsalwayshaveinitialparallelbranchingin
arteries,andmanyopensystemdoaswell.Parallelplumbing
allowsindividualorgansorbodyregionstoobtainfreshblood(or
hemolymph).
2)Therecanbemuscularvalvesonsomeofthebranchingparallel
vessels.Theseappearuniversallyinclosedsystemandoccurin
someopenones.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Circulatory Pathways and Vessels

64. Circulatoryfluidsaredrivenbypressureandcantransmitusefulforce.
Directingfluidflowinparallelmannercanserveanother
purpose–forceoftransmissiontospecificorgans.Tomovefromone
pointtoanotheritneedspressure(iscreatedbyapump,andisthe
drivingforceforfluidmovement).
Butitcanbeusedtoexertaforceforotherfunctions:
1)Movement
2)Ultrafiltration
3)Erection
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Circulatory Pathways and Vessels

65. Circulatoryfluidsaredrivenbypressureandcantransmitusefulforce.
1)Movement–hemolymphpressure(ratherthenskeletalmuscle)is
usedtoextendthelegsinarachnidssuchasspiders.Arteries
branchtothelegsandflowtothemcontrolled.Hemolymph
enteringintobentlegathighpressure(fromanopenartery)makes
thelegstraightenout.
2)Ultrafiltration–Bloodpressurecanforcewaterand
small,dissolvedsolutesoutofporesincapillarylinings.Thisis
usedintheinitialprocessofurineformationinthekidneyandfor
interactionswiththeECFinmanytissues.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Circulatory Pathways and Vessels

66. Circulatoryfluidsaredrivenbypressureandcantransmitusefulforce.
3) Erection–Bloodcanenteraflaccidorganunderhigh
pressure,andifexitingbloodisrestricted,theforceofthe
pressurewillinflatethatorgan.Thisoccursduringarousalof
erectilegenitalia(penis,clitoris)Scientistalsothinkitinflatesthe
sensitivesnoutoftheechidna(amonotreme)whichpokesits
snoutintotermiteandantneststofeed.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Circulatory Pathways and Vessels

67. Bloodflowthroughvesselsdependsonthepressuregradientand
vascularresistance.
Flowoffluidobeyscertainphysicallawcalledthehemodynamiclaw.
TheFlowrateofblood(volumeofbloodpassingthroughperunitof
time)isdirectlyproportionaltothepressuregradientandinversely
proportionaltovascularresistance.ExpressedinHemodynamicFlow
Law.
F = P/R or F = (P
1 -P
2) / R
where F = flow rate of fluid through a vessel
P = (P
1 -P
2) , P
1 =pressure at the inflow end of a vessel
P
2=pressure at the end flow end of a vessel
R = resistance of blood vessels
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Vessels: Flow Regulation and Hemodynamics

68. Circulatoryfluidsaredrivenbypressureandcantransmitusefulforce.
Factorsaffectingflowrate:
1)PressureGradient
2)Resistance
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Vessels: Flow Regulation and Hemodynamics

69. Circulatoryfluidsaredrivenbypressureandcantransmitusefulforce.
1)PressureGradient–thedifferenceinpressurebetweenthe
beginningandendofavessel–isthemaindrivingforceforflow
throughthevessel;thatis,
The blood flows from an area of higher pressure to an area of lower
pressure down a pressure gradient.
The greater the pressure gradient for forcing of blood through a
vessel, the greater the rate of flow through that vessel.
Gravityisanothermajorfactorinestablishingthepressure
gradient.Thisisparticularlyimportantinterrestrialanimalssuchas
humanandgiraffe.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Vessels: Flow Regulation and Hemodynamics

70. Circulatoryfluidsaredrivenbypressureandcantransmitusefulforce.
2)Resistance–isameasureofthehindrancetobloodflowthrougha
vesselcausedbyfrictionbetweenthemovingfluidandthe
stationaryvascularwalls.
As resistance to flow increases, it is more difficult for blood to
pass through the vessel, so flow decreases ( as long as the pressure
gradient remains unchanged).
When resistance increases, the pressure gradient must increase
correspondingly to maintain the same flow rate.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Vessels: Flow Regulation and Hemodynamics

71. Circulatoryfluidsaredrivenbypressureandcantransmitusefulforce.
2)Resistance–isameasureofthehindrancetobloodflowthrougha
vesselcausedbyfrictionbetweenthemovingfluidandthe
stationaryvascularwalls.
Resistancetobloodflowdependsonseveralfactors.(Laminar
flowisthetermforsmoothflow).Threekeyfactorsare:
-Viscosityoftheblood(thegreatertheviscosity,thegreatertheR)
-VesselLength(thelongerthevessel,thegreatertheR)
-VesselRadius(thesmallertheradius,thegreatertheR)
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Vessels: Flow Regulation and Hemodynamics

72. Inanopencirculatorysystem,bloodispumpedfromtheheart
throughbloodvesselsbutthenitleavesthebloodvesselsandenters
bodycavities(hemocoel),wheretheorgansarebathedinblood,or
sinuses(spaces)withintheorgans.
Bloodflowsslowlyinanopencirculatorysystembecausethereisno
bloodpressureafterthebloodleavesthebloodvessels.Theanimal
mustmoveitsmusclestomovethebloodwithinthespaces.
Themostwidelystudiedanimalswithopencirculationsare
dominatedbyasinglehemolymphspace.Widegroupofanimalsthat
haveopencirculatorysystemare:Mollusks(decapodsexceptsnails
andoctopuses)Insects,Crustaceans
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Open Circulation

73. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Open Circulation

74. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Open Circulation
Mollusks

75. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Open Circulation
Insects

76. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Open Circulation
Crustaceans
Theheartisamuscularsac,situateddorsally,beneaththe
carapace,anditgivesorigintosixarterialtrunks,whichconveythe
aeratedbloodtoallpartsofthebody.Theterminationsofthearteries
openintoaseriesofirregularvenoussinuses,whencethebloodis
collectedintoaprincipalventralsinus,anddistributedtothe
branchiae,whereitundergoesaeration.
Fromthegillsthenowaeratedbloodiscarriedbyaseriesofbranchial
vesselstoalargesac,whichisbadlytermedthe"pericardium,"and
whichenvelopsandsurroundstheheart.Thearterialbloodgains
accesstothecavityoftheheartbymeansofsixpairsofvalvular
fissures,whichallowoftheingressoftheblood,butprevent
regurgitation.Aportionofthevenousblood,however,isnotsenttothe
branchiae,butisreturneddirectly,withoutaeration,tothepericardium;
sothattheheartfinallydistributestothebodyamixtureofvenousand
arterialblood.

77. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Open Circulation
DiagramofthecirculationoftheLobster.Thesystemicarteriesare
shadedlongitudinally,theveinsaredotted,andthebranchial
vesselsareblack.hHeart;aaSystemicarteries;bbBranchial
vessels;ccVenoussinuses;ggBranchiae;pPericardium.

78. Inaclosedcirculatorysystem,bloodisnotfreeinacavity;itis
containedwithinbloodvessels.Valvespreventthebackflowofblood
withinthebloodvessels.
Widegroupofanimalsthathaveclosedcirculatorysystemare
Nemerteans,Annelids,Fish,Reptiles,Amphibians,Birds,Mammals.
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Closed Circulation

79. Fish
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Closed Circulation
Fishhaveatwo-chamberedheart
withoneatrium(A)andoneventricle
(V).
Thegillscontainmanycapillariesfor
gasexchange,sotheblood
pressureislowaftergoingthrough
thegills.Low-pressurebloodfrom
thegillsthengoesdirectlytothe
body,whichalsohasalargenumber
ofcapillaries.Theactivitylevelof
fishislimitedduetothelowrateof
bloodflowtothebody.

80. Amphibians
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Closed Circulation
Amphibianshavea3-chambered
heartwithtwoatriaandone
ventricle.
Bloodfromthelungs(pulmonary
flow)goestotheleftatrium.Blood
fromthebody(systemicflow)goes
totherightatrium.Bothatriaempty
intotheventriclewheresomemixing
occurs.
Theadvantageofthissystemisthat
thereishighpressureinvesselsthat
leadtoboththelungsandbody.

81. Reptiles
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Closed Circulation
Inmostreptiles,theventricleis
partiallydivided.
Thisreducesmixingofoxygenated
andunoxygenatedbloodinthe
ventricle.Thepartialdivisionofthe
ventricleisrepresentedbyadashed
line.

82. Birds,Mammals,Crocodilians
Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Closed Circulation
Birdsandmammals
(alsocrocodilians)haveafour-
chamberedheartwhichactsastwo
separatepumps.
Afterpassingthroughthe
body,bloodispumpedunderhigh
pressuretothelungs.Upon
returningfromthelungs,itis
pumpedunderhighpressuretothe
body.Thehighrateofoxygen-rich
bloodflowthroughthebodyenables
birdsandmammalstomaintainhigh
activitylevels.

83. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
Pathways: Closed Circulation

84. Animal Physiology: Mammalian Circulatory System Class Reporter: Elino, M. M. H.
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