TheThe Cardiocascular Cardiocascular

SystemSystem

Chapter 11Chapter 11

The Cardiovascular SystemThe Cardiovascular System

• A closed system of the heart and blood vesselsA closed system of the heart and blood vessels– The heart pumps bloodThe heart pumps blood– Blood vessels allow blood to circulate to all Blood vessels allow blood to circulate to all

parts of the bodyparts of the body

• The function of the cardiovascular system is to The function of the cardiovascular system is to deliver oxygen and nutrients and to remove deliver oxygen and nutrients and to remove carbon dioxide and other waste productscarbon dioxide and other waste products

The HeartThe Heart

• LocationLocation– Thorax between the lungsThorax between the lungs– Pointed apex directed toward left hipPointed apex directed toward left hip

• About the size of your fistAbout the size of your fist

The HeartThe Heart

Figure 11.1

The Heart: CoveringsThe Heart: Coverings

• Pericardium – a double serous membranePericardium – a double serous membrane– Visceral pericardiumVisceral pericardium

• Next to heartNext to heart– Parietal pericardiumParietal pericardium

• Outside layerOutside layer• Serous fluid fills the space between the layers of Serous fluid fills the space between the layers of

pericardiumpericardium

The Heart: Heart WallThe Heart: Heart Wall

• Three layersThree layers– EpicardiumEpicardium

•Outside layerOutside layer•This layer is This layer is

the parietal the parietal pericardiumpericardium

•Connective Connective tissue layertissue layer

– MyocardiumMyocardium•Middle layerMiddle layer•Mostly Mostly

cardiac cardiac musclemuscle

– EndocardiumEndocardium•Inner layerInner layer•EndotheliumEndothelium

External Heart AnatomyExternal Heart Anatomy

Figure 11.2a

The Heart: ChambersThe Heart: Chambers

• Right and left side act as separate pumpsRight and left side act as separate pumps• Four chambersFour chambers

– AtriaAtria• Receiving chambersReceiving chambers

–Right atriumRight atrium–Left atriumLeft atrium

– VentriclesVentricles• Discharging chambersDischarging chambers

–Right ventricleRight ventricle–Left ventricleLeft ventricle

Figure 11.2c

Blood CirculationBlood Circulation

Figure 11.3

The Heart: ValvesThe Heart: Valves

• Allow blood to flow in only one directionAllow blood to flow in only one direction• Four valvesFour valves

– Atrioventricular valves – between atria Atrioventricular valves – between atria and ventriclesand ventricles• Bicuspid valve (left)Bicuspid valve (left)• Tricuspid valve (right) Tricuspid valve (right)

– Semilunar valves between ventricle Semilunar valves between ventricle and arteryand artery• Pulmonary semilunar valvePulmonary semilunar valve• Aortic semilunar valveAortic semilunar valve

The Heart: ValvesThe Heart: Valves

• Valves open as blood is pumped throughValves open as blood is pumped through

• Held in place by Held in place by ““heart stringsheart strings””

• Close to prevent backflowClose to prevent backflow

Operation of Heart ValvesOperation of Heart Valves

Figure 11.4

The Heart: Associated Great The Heart: Associated Great VesselsVessels

• AortaAorta

– Leaves left Leaves left ventricleventricle

• Pulmonary arteriesPulmonary arteries

– Leave right Leave right ventricleventricle

• Vena cavaVena cava

– Enters right Enters right atriumatrium

• Pulmonary veins (four)Pulmonary veins (four)

– Enter left atriumEnter left atrium

Coronary CirculationCoronary Circulation

• Blood in the heart chambers does not Blood in the heart chambers does not nourish the myocardiumnourish the myocardium

• The heart has its own nourishing The heart has its own nourishing circulatory systemcirculatory system

– Coronary arteriesCoronary arteries

– Cardiac veinsCardiac veins

– Blood empties into the right atrium Blood empties into the right atrium via the coronary sinusvia the coronary sinus

The Heart: Conduction SystemThe Heart: Conduction System

• Intrinsic conduction system Intrinsic conduction system (nodal system)(nodal system)

– Heart muscle cells contract, without Heart muscle cells contract, without nerve impulses, in a regular, continuous nerve impulses, in a regular, continuous wayway

The Heart: Conduction SystemThe Heart: Conduction System

• Special tissue sets the paceSpecial tissue sets the pace

• Sinoatrial nodeSinoatrial node

–Pacemaker of the heartPacemaker of the heart

• Atrioventricular nodeAtrioventricular node

• Atrioventricular bundleAtrioventricular bundle

• Bundle branchesBundle branches

• Purkinje fibersPurkinje fibers

Heart ContractionsHeart Contractions

• Contraction is initiated by the sinoatrial nodeContraction is initiated by the sinoatrial node

• Sequential stimulation occurs at other Sequential stimulation occurs at other autorhythmic cellsautorhythmic cells

Heart ContractionsHeart Contractions

Figure 11.5

Filling of Heart Chambers – the Filling of Heart Chambers – the Cardiac CycleCardiac Cycle

Figure 11.6

The Heart: Cardiac CycleThe Heart: Cardiac Cycle

• Atria contract simultaneouslyAtria contract simultaneously

• Atria relax, then ventricles contractAtria relax, then ventricles contract

• Systole = contractionSystole = contraction

• Diastole = relaxationDiastole = relaxation

The Heart: Cardiac CycleThe Heart: Cardiac Cycle

• Cardiac cycle – events of one complete heart Cardiac cycle – events of one complete heart beatbeat

– Mid-to-late diastole – blood flows into Mid-to-late diastole – blood flows into ventriclesventricles

– Ventricular systole – blood pressure builds Ventricular systole – blood pressure builds before ventricle contracts, pushing out bloodbefore ventricle contracts, pushing out blood

– Early diastole – atria finish re-filling, Early diastole – atria finish re-filling, ventricular pressure is lowventricular pressure is low

The Heart: Cardiac OutputThe Heart: Cardiac Output• Cardiac output (CO)Cardiac output (CO)

– Amount of blood pumped by each side Amount of blood pumped by each side of the heart in one minuteof the heart in one minute

– CO = (heart rate [HR]) x (stroke volume CO = (heart rate [HR]) x (stroke volume [SV])[SV])

• Stroke volumeStroke volume– Volume of blood pumped by each Volume of blood pumped by each

ventricle in one contractionventricle in one contraction

Cardiac Output RegulationCardiac Output Regulation

Figure 11.7

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Cardiac Cath AngiolplastyCardiac Cath Angiolplasty

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11 The Cardiovascular The Cardiovascular SystemSystem

The Heart: Regulation of Heart The Heart: Regulation of Heart RateRate

• Stroke volume usually remains Stroke volume usually remains relatively constantrelatively constant

– StarlingStarling’’s law of the heart – the more s law of the heart – the more that the cardiac muscle is stretched, that the cardiac muscle is stretched, the stronger the contractionthe stronger the contraction

• Changing heart rate is the most Changing heart rate is the most common way to change cardiac outputcommon way to change cardiac output

The Heart: Regulation of Heart The Heart: Regulation of Heart RateRate

• Increased heart Increased heart raterate– Sympathetic Sympathetic

nervous systemnervous system•CrisisCrisis•Low blood Low blood

pressurepressure

– HormonesHormones•EpinephrineEpinephrine•ThyroxineThyroxine

– ExerciseExercise– Decreased Decreased

blood volumeblood volume

The Heart: Regulation of Heart The Heart: Regulation of Heart RateRate

• Decreased heart rateDecreased heart rate

– Parasympathetic nervous systemParasympathetic nervous system

– High blood pressure or blood High blood pressure or blood volumevolume

– Dereased venous returnDereased venous return

Blood Vessels: The Vascular Blood Vessels: The Vascular SystemSystem

• Taking blood to the tissues and backTaking blood to the tissues and back– ArteriesArteries– ArteriolesArterioles– CapillariesCapillaries– VenulesVenules– VeinsVeins

Figure 11.8a

The Vascular SystemThe Vascular System

Figure 11.8b

Blood Vessels: AnatomyBlood Vessels: Anatomy

• Three layers (tunics)Three layers (tunics)– Tunic intimaTunic intima

• EndotheliumEndothelium– Tunic mediaTunic media

• Smooth muscleSmooth muscle• Controlled by sympathetic Controlled by sympathetic

nervous systemnervous system– Tunic externaTunic externa

• Mostly fibrous connective tissueMostly fibrous connective tissue

Differences Between Blood Vessel Differences Between Blood Vessel TypesTypes

• Walls of arteries are the thickestWalls of arteries are the thickest

• Lumens of veins are largerLumens of veins are larger

• Skeletal muscle Skeletal muscle ““milksmilks”” blood in veins blood in veins toward the hearttoward the heart

• Walls of capillaries are only one cell Walls of capillaries are only one cell layer thick to allow for exchanges layer thick to allow for exchanges between blood and tissuebetween blood and tissue

Movement of Blood Through Movement of Blood Through VesselsVessels

• Most arterial Most arterial blood is pumped blood is pumped by the heartby the heart

• Veins use the Veins use the milking action of milking action of muscles to help muscles to help move bloodmove blood

Figure 11.9

Capillary BedsCapillary Beds• Capillary beds Capillary beds

consist of two types consist of two types of vesselsof vessels

– Vascular shunt – Vascular shunt – directly connects directly connects an arteriole to a an arteriole to a venulevenule

Figure 11.10

Capillary BedsCapillary Beds• True capillaries – True capillaries –

exchange vesselsexchange vessels

• Oxygen and Oxygen and nutrients cross nutrients cross to cellsto cells

• Carbon dioxide Carbon dioxide and metabolic and metabolic waste products waste products cross into cross into bloodblood Figure 11.10

Diffusion at Capillary BedsDiffusion at Capillary Beds

Figure 11.20

Major Arteries of Systemic Major Arteries of Systemic CirculationCirculation

Figure 11.11

Major Veins of Systemic Major Veins of Systemic CirculationCirculation

Figure 11.12

Arterial Supply of the BrainArterial Supply of the Brain

Figure 11.13

Hepatic Portal CirculationHepatic Portal Circulation

Figure 11.14

Circulation to the FetusCirculation to the Fetus

Figure 11.15

PulsePulse• Pulse – Pulse –

pressure wave pressure wave of bloodof blood

• Monitored at Monitored at ““pressure pressure pointspoints”” where where pulse is easily pulse is easily palpatedpalpated

Figure 11.16

Blood PressureBlood Pressure

• Measurements by health professionals are Measurements by health professionals are made on the pressure in large arteriesmade on the pressure in large arteries

– Systolic – pressure at the peak of Systolic – pressure at the peak of ventricular contractionventricular contraction

– Diastolic – pressure when ventricles relaxDiastolic – pressure when ventricles relax

• Pressure in blood vessels decreases as the Pressure in blood vessels decreases as the distance away from the heart increasesdistance away from the heart increases

Measuring Arterial Blood Measuring Arterial Blood PressurePressure

Figure 11.18

Figure 11.17

Comparison of Blood Pressures Comparison of Blood Pressures in Different Vesselsin Different Vessels

Blood Pressure: Effects of Blood Pressure: Effects of FactorsFactors

• Neural factorsNeural factors

– Autonomic nervous system Autonomic nervous system adjustments (sympathetic division)adjustments (sympathetic division)

• Renal factorsRenal factors

– Regulation by altering blood volumeRegulation by altering blood volume

– Renin – hormonal controlRenin – hormonal control

Blood Pressure: Effects of Blood Pressure: Effects of FactorsFactors

• TemperatureTemperature

– Heat has a vasodilation effectHeat has a vasodilation effect

– Cold has a vasoconstricting effectCold has a vasoconstricting effect

• ChemicalsChemicals

– Various substances can cause Various substances can cause increases or decreasesincreases or decreases

• DietDiet

Factors Determining Blood Factors Determining Blood PressurePressure

Figure 11.19

Variations in Blood PressureVariations in Blood Pressure

• Human normal range is variableHuman normal range is variable– NormalNormal

• 140–110 mm Hg systolic140–110 mm Hg systolic• 80–75 mm Hg diastolic80–75 mm Hg diastolic

– HypotensionHypotension• Low systolic (below 110 mm HG)Low systolic (below 110 mm HG)• Often associated with illnessOften associated with illness

– HypertensionHypertension• High systolic (above 140 mm HG)High systolic (above 140 mm HG)• Can be dangerous if it is chronicCan be dangerous if it is chronic

Capillary ExchangeCapillary Exchange

• Substances exchanged due to Substances exchanged due to concentration gradientsconcentration gradients

– Oxygen and nutrients leave the bloodOxygen and nutrients leave the blood

– Carbon dioxide and other wastes leave Carbon dioxide and other wastes leave the cellsthe cells

Capillary Exchange: MechanismsCapillary Exchange: Mechanisms

• Direct diffusion across plasma Direct diffusion across plasma membranesmembranes

• Endocytosis or exocytosisEndocytosis or exocytosis

• Some capillaries have gaps Some capillaries have gaps (intercellular clefts)(intercellular clefts)

– Plasma membrane not joined by tight Plasma membrane not joined by tight junctionsjunctions

• Fenestrations of some capillariesFenestrations of some capillaries

– Fenestrations = poresFenestrations = pores

The Cardiovascular SystemThe Cardiovascular System

•Three Major Elements – Three Major Elements – Heart, Blood Vessels, & Heart, Blood Vessels, & BloodBlood

–1. 1. The HeartThe Heart- cardiac - cardiac muscle tissuemuscle tissue–highly interconnected cellshighly interconnected cells–four chambersfour chambers

•Right atriumRight atrium•Right ventricleRight ventricle•Left atriumLeft atrium•Left ventricleLeft ventricle

Pathway of the Pathway of the bloodblood•Superior Vena CavaSuperior Vena Cava

•Right AtriumRight Atrium•Tricuspid ValveTricuspid Valve•Right VentricleRight Ventricle•Pulmonary Semilunar ValvePulmonary Semilunar Valve•LungsLungs•Pulmonary VeinPulmonary Vein•Bicuspid ValveBicuspid Valve•Left VentricleLeft Ventricle•Aortic Semilunar ValveAortic Semilunar Valve•AortaAorta•To the bodies organs & cellsTo the bodies organs & cells

CircuitsCircuits

•Pulmonary circuitPulmonary circuit–The blood pathway The blood pathway between the right side of between the right side of the heart, to the lungs, and the heart, to the lungs, and back to the left side of the back to the left side of the heart.heart.

•Systemic circuitSystemic circuit–The pathway between The pathway between the left and right sides of the left and right sides of the heart.the heart.

The Cardiovascular SystemThe Cardiovascular System2. Blood Vessels -A network of tubes2. Blood Vessels -A network of tubes

–ArteriesArteriesarteriolesarterioles move away from the heart move away from the heart•Elastic FibersElastic Fibers•Circular Smooth MuscleCircular Smooth Muscle

–Capillaries Capillaries – where gas exchange takes place.– where gas exchange takes place.•One cell thickOne cell thick•Serves the Respiratory SystemServes the Respiratory System

–VeinsVeinsVenulesVenules moves towards the heart moves towards the heart•Skeletal Muscles contract to force blood back from legsSkeletal Muscles contract to force blood back from legs•One way valuesOne way values•When they break - varicose veins formWhen they break - varicose veins form

Disorders of the Circulatory Disorders of the Circulatory SystemSystem

• Anemia Anemia - lack of iron in the blood, low RBC count- lack of iron in the blood, low RBC count

• LeukemiaLeukemia - white blood cells proliferate wildly, causing - white blood cells proliferate wildly, causing anemiaanemia

• Hemophilia Hemophilia - bleeder- bleeder’’s disease, due to lack of fibrinogen in s disease, due to lack of fibrinogen in thrombocytesthrombocytes

• Heart MurmurHeart Murmur - abnormal heart beat, caused by valve - abnormal heart beat, caused by valve problemsproblems

• Heart attackHeart attack - blood vessels around the heart become - blood vessels around the heart become blocked with plaque, also called blocked with plaque, also called myocardial infarctionmyocardial infarction

Unit 11B – The HeartUnit 11B – The Heart

The Heart In Greater DepthThe Heart In Greater Depth

Functions of the HeartFunctions of the Heart

• Generating Generating bloodblood pressure pressure

• Routing Routing bloodblood

– Heart separates pulmonary and Heart separates pulmonary and systemic circulationssystemic circulations

Functions of the HeartFunctions of the Heart

• Ensuring one-way Ensuring one-way bloodblood flow flow

– Heart valves ensure one-way Heart valves ensure one-way flowflow

• Regulating Regulating bloodblood supply supply

– Changes in contraction rate and Changes in contraction rate and force match blood delivery to force match blood delivery to changing metabolic needschanging metabolic needs

Size, Shape, Location Size, Shape, Location of the Heartof the Heart

•Size of a closed fistSize of a closed fist•ShapeShape

–ApexApex: Blunt : Blunt rounded point of rounded point of conecone–BaseBase: Flat part at : Flat part at opposite of end of opposite of end of conecone

•Located in thoracic Located in thoracic cavity in mediastinumcavity in mediastinum

Heart Cross SectionHeart Cross Section

PericardiumPericardium

Heart WallHeart Wall

• Three layers of tissueThree layers of tissue– EpicardiumEpicardium: This serous membrane of : This serous membrane of

smooth outer surface of heartsmooth outer surface of heart– MyocardiumMyocardium: Middle layer composed : Middle layer composed

of cardiac muscle cell and of cardiac muscle cell and responsibility for heart contractingresponsibility for heart contracting

– EndocardiumEndocardium: Smooth inner surface of : Smooth inner surface of heart chambersheart chambers

Heart WallHeart Wall

External AnatomyExternal Anatomy

•Four chambersFour chambers–2 atria2 atria–2 ventricles2 ventricles

•AuriclesAuricles•Major veinsMajor veins

–Superior vena Superior vena cavacava–Pulmonary veinsPulmonary veins

•Major arteriesMajor arteries–AortaAorta–Pulmonary trunkPulmonary trunk

External AnatomyExternal Anatomy

Coronary CirculationCoronary Circulation

Heart ValvesHeart Valves

•AtrioventricularAtrioventricular–TricuspidTricuspid–Bicuspid or Bicuspid or mitralmitral

•SemilunarSemilunar–AorticAortic–PulmonaryPulmonary

•Prevent blood from Prevent blood from flowing backflowing back

Heart ValvesHeart Valves

Function of the Heart Function of the Heart ValvesValves

Blood Flow Through HeartBlood Flow Through Heart

Systemic and PulmonarySystemic and PulmonaryCirculationCirculation

Heart SkeletonHeart Skeleton

•Consists of plate Consists of plate of fibrous of fibrous connective tissue connective tissue between atria and between atria and ventriclesventricles

•Fibrous rings Fibrous rings around valves to around valves to supportsupport

Heart SkeletonHeart Skeleton

•Serves as electrical Serves as electrical insulation between insulation between atria and ventriclesatria and ventricles

•Provides site for Provides site for muscle attachmentmuscle attachment

Cardiac MuscleCardiac Muscle

• Elongated, Elongated, branching cells branching cells containing 1-2 containing 1-2 centrally located centrally located nucleinuclei

• Contains actin and Contains actin and myosin myosin myofilaments myofilaments

Cardiac MuscleCardiac Muscle

• Intercalated Intercalated disks: disks: Specialized Specialized cell-cell contactscell-cell contacts

• Desmosomes Desmosomes hold cells hold cells together and gap together and gap junctions allow junctions allow action potentialsaction potentials

Cardiac MuscleCardiac Muscle

• Electrically, Electrically, cardiac muscle cardiac muscle behaves as single behaves as single unitunit

Conducting System of Conducting System of HeartHeart

Electrical PropertiesElectrical Properties

• Resting membrane potential (Resting membrane potential (RMPRMP) ) presentpresent

• Action potentialsAction potentials

– Rapid depolarization followed by rapid, Rapid depolarization followed by rapid, partial early repolarization. Prolonged partial early repolarization. Prolonged period of slow repolarization which is period of slow repolarization which is plateau phase and a rapid final plateau phase and a rapid final repolarization phaserepolarization phase

– Voltage-gated channelsVoltage-gated channels

Action Potentials inAction Potentials inSkeletal and Cardiac Skeletal and Cardiac

MuscleMuscle

SA Node Action PotentialSA Node Action Potential

Refractory PeriodRefractory Period

• AbsoluteAbsolute: Cardiac muscle cell completely : Cardiac muscle cell completely insensitive to further stimulationinsensitive to further stimulation

• RelativeRelative: Cell exhibits reduced sensitivity : Cell exhibits reduced sensitivity to additional stimulationto additional stimulation

• Long refractory period prevents tetanic Long refractory period prevents tetanic contractionscontractions

ElectrocardiogramElectrocardiogram

• Action potentials Action potentials through through myocardium myocardium during cardiac during cardiac cycle produces cycle produces electric currents electric currents than can be than can be measured measured

ElectrocardiogramElectrocardiogram

• PatternPattern– P wave P wave

• Atria Atria depolarizationdepolarization

ElectrocardiogramElectrocardiogram

• PatternPattern

– QRS complexQRS complex• Ventricle Ventricle

depolarizationdepolarization• Atria Atria

repolarizationrepolarization

ElectrocardiogramElectrocardiogram

• PatternPattern

– T wave:T wave: • Ventricle Ventricle

repolarizationrepolarization

Cardiac ArrhythmiasCardiac Arrhythmias

• TachycardiaTachycardia: Heart rate in excess of : Heart rate in excess of 100bpm100bpm

• BradycardiaBradycardia: Heart rate less than 60 : Heart rate less than 60 bpmbpm

• Sinus arrhythmiaSinus arrhythmia: Heart rate varies : Heart rate varies 5% during respiratory cycle and up to 5% during respiratory cycle and up to 30% during deep respiration30% during deep respiration

• peoplepeople

Cardiac ArrhythmiasCardiac Arrhythmias

• Premature atrial contractionsPremature atrial contractions: : Occasional shortened intervals Occasional shortened intervals between one contraction and between one contraction and succeeding, frequently occurs in succeeding, frequently occurs in healthy peoplehealthy people

Alterations in Alterations in ElectrocardiogramElectrocardiogram

Cardiac CycleCardiac Cycle

• Heart is two pumps that work together, Heart is two pumps that work together, right and left halfright and left half

• Repetitive contraction (Repetitive contraction (systolesystole) and ) and relaxation (relaxation (diastolediastole) of heart chambers) of heart chambers

• Blood moves through circulatory system Blood moves through circulatory system from areas of higher to lower pressure.from areas of higher to lower pressure.

– Contraction of heart produces the Contraction of heart produces the pressurepressure

Cardiac CycleCardiac Cycle

Events during Cardiac Events during Cardiac CycleCycle

Heart SoundsHeart Sounds

• First heart sound or First heart sound or ““lubblubb””– Atrioventricular valves and Atrioventricular valves and

surrounding fluid vibrations as surrounding fluid vibrations as valves close at beginning of valves close at beginning of ventricular systoleventricular systole

Heart SoundsHeart Sounds

Second heart sound or Second heart sound or ““duppdupp””– Results from closure of aortic and Results from closure of aortic and

pulmonary semilunar valves at pulmonary semilunar valves at beginning of ventricular diastole, beginning of ventricular diastole, lasts longerlasts longer

Heart SoundsHeart Sounds

• Third heart sound (occasional)Third heart sound (occasional)

– Caused by turbulent blood flow Caused by turbulent blood flow into ventricles and detected near into ventricles and detected near end of first one-third of diastoleend of first one-third of diastole

Location of Heart ValvesLocation of Heart Valves

Regulation of the HeartRegulation of the Heart

• Intrinsic regulationIntrinsic regulation: Results from : Results from normal functional normal functional characteristics, not on neural or characteristics, not on neural or hormonal regulationhormonal regulation– StarlingStarling’’s law of the hearts law of the heart

• Extrinsic regulationExtrinsic regulation: Involves : Involves neural and hormonal controlneural and hormonal control

Regulation of the HeartRegulation of the Heart

– Parasympathetic stimulationParasympathetic stimulation

•Supplied by vagus nerve, Supplied by vagus nerve, decreases heart rate, decreases heart rate, acetylcholine secretedacetylcholine secreted

– Sympathetic stimulationSympathetic stimulation

•Supplied by cardiac nerves, Supplied by cardiac nerves, increases heart rate and force increases heart rate and force of contraction, epinephrine of contraction, epinephrine and norepinephrine releasedand norepinephrine released

Heart HomeostasisHeart Homeostasis

• Effect of blood pressureEffect of blood pressure

– Baroreceptors monitor blood Baroreceptors monitor blood pressurepressure

• Effect of pH, carbon dioxide, oxygenEffect of pH, carbon dioxide, oxygen

– Chemoreceptors monitor Chemoreceptors monitor

Heart HomeostasisHeart Homeostasis

• Effect of extracellular ion concentrationEffect of extracellular ion concentration

– Increase or decrease in extracellular Increase or decrease in extracellular KK++ decreases heart rate decreases heart rate

• Effect of body temperatureEffect of body temperature

– Heart rate increases when body Heart rate increases when body temperature increases, heart rate temperature increases, heart rate decreases when body temperature decreases when body temperature decreasesdecreases

Effects of Aging on the Effects of Aging on the HeartHeart

• Gradual changes in heart Gradual changes in heart function, minor under resting function, minor under resting condition, more significant condition, more significant during exerciseduring exercise

• Hypertrophy of left ventricleHypertrophy of left ventricle

• Maximum heart rate decreasesMaximum heart rate decreases

Effects of Aging on the Effects of Aging on the HeartHeart

• Increased tendency for valves to Increased tendency for valves to function abnormally and function abnormally and arrhythmias to occurarrhythmias to occur

• Increased oxygen consumption Increased oxygen consumption required to pump same amount required to pump same amount of bloodof blood

Developmental Aspects of the Developmental Aspects of the Cardiovascular SystemCardiovascular System

• A simple A simple ““tube hearttube heart”” develops in the develops in the embryo and pumps by the fourth weekembryo and pumps by the fourth week

• The heart becomes a four-chambered The heart becomes a four-chambered organ by the end of seven weeksorgan by the end of seven weeks

• Few structural changes occur after the Few structural changes occur after the seventh weekseventh week

The Closed Circulatory SystemThe Closed Circulatory System•Humans have a Humans have a closed circulatory systemclosed circulatory system, typical , typical of all vertebrates, in which blood is confined to of all vertebrates, in which blood is confined to vessels and is distinct from the interstitial fluid.vessels and is distinct from the interstitial fluid.

–The heart pumps blood into large vessels The heart pumps blood into large vessels that branch into smaller ones leading into the that branch into smaller ones leading into the organs.organs.

–Materials are exchanged by diffusion between the Materials are exchanged by diffusion between the blood and the interstitial fluid bathing the cells.blood and the interstitial fluid bathing the cells.