PhysiologyPhysiology

Cardiovascular SystemCardiovascular System

Cardiac Muscle and the Cardiac Muscle and the HeartHeart

MyocardiumMyocardium Heart muscleHeart muscle

Sits in the media stinum of the thoracic Sits in the media stinum of the thoracic cavitycavity

Left Axis DeviationLeft Axis Deviation May have a right axis deviation with obesity May have a right axis deviation with obesity

and/or pregnancyand/or pregnancy May hang in the middle of the thoracic cavity May hang in the middle of the thoracic cavity

if the individual is very tallif the individual is very tall

The HeartThe Heart

The heart has four chambersThe heart has four chambers Right and left atriumRight and left atrium

Atria is pluralAtria is plural Right and left ventricleRight and left ventricle

Blood Flow Through the Blood Flow Through the HeartHeart

Deoxygenated blood enters the right Deoxygenated blood enters the right atrium of the heart through the atrium of the heart through the superior and inferior vena cavasuperior and inferior vena cava Deoxygenated bloodDeoxygenated blood

Has less than 50% oxygen saturation on Has less than 50% oxygen saturation on hemoglobinhemoglobin

HemoglobinHemoglobin

Quaternary StructureQuaternary Structure Four Globin proteinsFour Globin proteins

Globin carries COGlobin carries CO22, H, H++, PO, PO44

Four Heme attach to each GlobinFour Heme attach to each Globin Heme binds OHeme binds O22 and CO and CO Heme contains an Iron ionHeme contains an Iron ion

About 1 million hemoglobin molecules per red About 1 million hemoglobin molecules per red blood cellblood cell

Oxygen carrying capacity of approximately 5 Oxygen carrying capacity of approximately 5 minutesminutes

Heart Valves Ensure One-Heart Valves Ensure One-Way Flow of Blood in the Way Flow of Blood in the

HeartHeart Atrioventricular ValvesAtrioventricular Valves

Located between the atria and the Located between the atria and the ventricleventricle

Labeled Right and LeftLabeled Right and Left Right Valve is also called TricuspidRight Valve is also called Tricuspid Left Valve is also called Bicuspid or Left Valve is also called Bicuspid or

MitralMitral

Heart ValvesHeart Valves Papillary muscles are attached to the Papillary muscles are attached to the

chordae tendinaechordae tendinae Chordae tendinae are also connected to Chordae tendinae are also connected to

the AV valvesthe AV valves Just prior to ventricular contraction the Just prior to ventricular contraction the

papillary muscles contract and pull papillary muscles contract and pull downward on the chordae tendinaedownward on the chordae tendinae

The chordae tendinae pull downward on The chordae tendinae pull downward on the AV valvesthe AV valves This prevents the valves from prolapsing and This prevents the valves from prolapsing and

blood regurgitating back into the atria.blood regurgitating back into the atria.

Follow Path of Blood Follow Path of Blood through Heartthrough Heart

Blood FlowBlood Flow Due to gravity deoxygenated blood enters the Due to gravity deoxygenated blood enters the

right/left atrium (by way of the pulmonary veins) right/left atrium (by way of the pulmonary veins) and flows through the open AV valve directly into and flows through the open AV valve directly into the ventriclesthe ventricles

The filling of the ventricles with blood pushes the The filling of the ventricles with blood pushes the AV valve upwardAV valve upward They are held in place by the chordae tendinaeThey are held in place by the chordae tendinae

Right before the valves shuts completely the Right before the valves shuts completely the atria contract from the base towards the apex of atria contract from the base towards the apex of the heart in order to squeeze more blood into the the heart in order to squeeze more blood into the ventricleventricle The AV valves snapping shut creates the The AV valves snapping shut creates the ““LubLub”” sound of sound of

the heart beatthe heart beat

Blood FlowBlood Flow

When the AV valves are shut the When the AV valves are shut the Pulmonary and Aortic semi-lunar Pulmonary and Aortic semi-lunar valves are also shutvalves are also shut DiastoleDiastole Quiescence of the heartQuiescence of the heart

Myocardial Contraction Myocardial Contraction (Systole)(Systole)

After Diastole occurs the ventricles begin to After Diastole occurs the ventricles begin to contract from the apex towards the base of the contract from the apex towards the base of the heartheart

The deoxygenated blood on the right side of the The deoxygenated blood on the right side of the heart is pushed through the pulmonary trunk heart is pushed through the pulmonary trunk after opening the semi-lunar valve to the after opening the semi-lunar valve to the pulmonary arteries into the lungs to become pulmonary arteries into the lungs to become oxygenated.oxygenated.

The oxygenated blood on the left side of the The oxygenated blood on the left side of the heart is pushed through the aorta after opening heart is pushed through the aorta after opening the semi-lunar valve into the systemic circulationthe semi-lunar valve into the systemic circulation

Blood FlowBlood Flow

The Ventricles do not have enough The Ventricles do not have enough pressure to push all of the blood out pressure to push all of the blood out of the pulmonary trunk and aortaof the pulmonary trunk and aorta The blood falls back down due to The blood falls back down due to

gravitygravity The semi-lunar valves snap shutThe semi-lunar valves snap shut

The The ““DupDup”” sound of the heart beat sound of the heart beat

Blood FlowBlood Flow

Blood is always flowing from a Blood is always flowing from a region of higher pressure to a region region of higher pressure to a region of lower pressureof lower pressure

Atrial and Ventricular Atrial and Ventricular DiastoleDiastole

The heart at restThe heart at rest The atria are filling with blood from The atria are filling with blood from

the veinsthe veins The ventricles have just completed The ventricles have just completed

contractioncontraction AV valves are openAV valves are open Blood flow due to gravityBlood flow due to gravity

Atrial Systole: Completion Atrial Systole: Completion of Ventricular Fillingof Ventricular Filling

The last 20% of the blood fills the The last 20% of the blood fills the ventricles due to atrial contractionventricles due to atrial contraction

Early Ventricular Early Ventricular ContractionContraction

As the atria are contracting As the atria are contracting Depolarization wave moves through the Depolarization wave moves through the

conducting cells of the AV node down to conducting cells of the AV node down to the Purkinje fibers to the apex of the heartthe Purkinje fibers to the apex of the heart

Ventricular systole beginsVentricular systole begins AV Valves close due to Ventricular AV Valves close due to Ventricular

pressurepressure First Heart SoundFirst Heart Sound

S1 = Lub of Lub-DupS1 = Lub of Lub-Dup

Isovolumic Ventricular Isovolumic Ventricular ContractionContraction

AV and Semilunar Valves closedAV and Semilunar Valves closed Ventricles continue to contractVentricles continue to contract

Atrial muscles are repolarizing and Atrial muscles are repolarizing and relaxingrelaxing

Blood flows into the atria againBlood flows into the atria again

Ventricular EjectionVentricular Ejection

The pressure in the ventricles The pressure in the ventricles pushes the blood through the pushes the blood through the pulmonary trunk and aortapulmonary trunk and aorta Semi-lunar valves openSemi-lunar valves open Blood is ejected from the heartBlood is ejected from the heart

Ventricular Relaxation and Ventricular Relaxation and Second Heart SoundSecond Heart Sound

At the end of ventricular ejectionAt the end of ventricular ejection Ventricles begin to repolarize and relaxVentricles begin to repolarize and relax Ventricular pressure decreasesVentricular pressure decreases Blood falls backward into the heartBlood falls backward into the heart Blood is caught in cusps of the semi-Blood is caught in cusps of the semi-

lunar valvelunar valve Valves snap shutValves snap shut S2 – Dup of lub-dupS2 – Dup of lub-dup

Isovolumetric Ventricular Isovolumetric Ventricular RelaxationRelaxation

Semilunar valves closeSemilunar valves close AV valves closedAV valves closed The volume of blood in the ventricles The volume of blood in the ventricles

is not changingis not changing When ventricular pressure is less When ventricular pressure is less

than atrial pressure the AV valves than atrial pressure the AV valves open againopen again The Cardiac Cycle begins againThe Cardiac Cycle begins again

Cardiac CirculationCardiac Circulation

Blood flowing through the heart has Blood flowing through the heart has a high fat contenta high fat content

Curvature as well as diameter of the Curvature as well as diameter of the arteries is important to blood flow arteries is important to blood flow through the heartthrough the heart Vasoconstriction due to sympathetic Vasoconstriction due to sympathetic

nervous system inputnervous system input Norepinephrine/EpinephrineNorepinephrine/Epinephrine

Alpha Receptors not BetaAlpha Receptors not Beta

Myocardial InfarctionMyocardial Infarction

Heart AttackHeart Attack Due to plaque build up in the arteriesDue to plaque build up in the arteries

Decrease in blood flow to myocardiumDecrease in blood flow to myocardium Depolarization of muscle cannot occur Depolarization of muscle cannot occur

due to myocardial deathdue to myocardial death Myocardium doesnMyocardium doesn’’t work as a t work as a

syncytium any longersyncytium any longer Destruction of gap junction or Destruction of gap junction or

““connexonsconnexons””

AtherosclerosisAtherosclerosis

Plaque in the arteriesPlaque in the arteries Elevated Cholesterol in the bloodElevated Cholesterol in the blood

Cholesterol is cleared by the liverCholesterol is cleared by the liver HDL – High Density LipoproteinHDL – High Density Lipoprotein

H for healthyH for healthy LDL – Low Density LipoproteinLDL – Low Density Lipoprotein

L for LethalL for Lethal Omega 3 fatty acidsOmega 3 fatty acids

““RotorooterRotorooter”” for the arteries for the arteries

If a Patient Has a Left If a Patient Has a Left Atrial Infarction ThenAtrial Infarction Then

What happens to heart contraction and What happens to heart contraction and blood flow through the heart?blood flow through the heart?

What type of symptoms might your What type of symptoms might your patient have?patient have?

What recommendations might you give What recommendations might you give the patient to live a better life?the patient to live a better life? There are some things they better not do or There are some things they better not do or

they will die. What are these things (in they will die. What are these things (in general)?general)?

Angioplasty/Open Heart Angioplasty/Open Heart SurgerySurgery

Cardiac Muscle & Cardiac Muscle & HeartHeart

Cardiac Muscle & Cardiac Muscle & HeartHeart

Heart muscle cells:Heart muscle cells: 99% contractile99% contractile 1% autorrhythmic1% autorrhythmic

Cardiac Muscle Cells Cardiac Muscle Cells Contract Without Nervous Contract Without Nervous

StimulationStimulation Autorhythmic CellsAutorhythmic Cells

Pacemaker Cells set the rate of the Pacemaker Cells set the rate of the heartbeatheartbeat Sinoatrial NodeSinoatrial Node Atriventricular NodeAtriventricular Node

Distinct from contractile myocardial Distinct from contractile myocardial cellscells SmallerSmaller Contain few contractile proteinsContain few contractile proteins http://www.youtube.com/watch?http://www.youtube.com/watch?

v=7K2icszdxQcv=7K2icszdxQc

Excitation-Contraction (EC) Excitation-Contraction (EC) Coupling in Cardiac MuscleCoupling in Cardiac MuscleExcitation-Contraction (EC) Excitation-Contraction (EC) Coupling in Cardiac MuscleCoupling in Cardiac Muscle

Contraction occurs by same sliding filament Contraction occurs by same sliding filament activity as in skeletal muscleactivity as in skeletal muscle

some differences:some differences: AP is from pacemaker (SA node)AP is from pacemaker (SA node) AP opens voltage-gated CaAP opens voltage-gated Ca2+ 2+ channels in cell channels in cell

membranemembrane CaCa2+ 2+ induces Cainduces Ca2+ 2+ release from SR storesrelease from SR stores Relaxation similar to skeletal muscleRelaxation similar to skeletal muscle

CaCa2+ 2+ removal requires Caremoval requires Ca22 -ATPase (into SR) & -ATPase (into SR) & NaNa++/Ca/Ca2+2+ antiport antiport (into ECF)(into ECF)

[Na[Na++] restored via?] restored via?http://www.youtube.com/watch?v=rIVCuC-Etc0http://www.youtube.com/watch?v=rIVCuC-Etc0

Cardiac ContractionCardiac Contraction Action Potentials originate in Autorhythmic CellsAction Potentials originate in Autorhythmic Cells

AP spreads through gap junctionAP spreads through gap junction Protein tunnels that connect myocardial cellsProtein tunnels that connect myocardial cells

AP moves across the sarcolemma and into the t-AP moves across the sarcolemma and into the t-tubulestubules

Voltage-gated Ca Voltage-gated Ca +2+2 channels in the cell channels in the cell membrane openmembrane open

Ca Ca +2+2 enters the cell which then opens enters the cell which then opens ryanodine receptor-channelsryanodine receptor-channels

Ryanodine receptor channels are located Ryanodine receptor channels are located on the sarcoplasmic reticulum and Ca on the sarcoplasmic reticulum and Ca +2+2 diffuses into the cells to diffuses into the cells to ““sparkspark”” muscle muscle contractioncontraction

Cross bridge formation and contraction Cross bridge formation and contraction occursoccurs

Myocardial Contractile Myocardial Contractile CellsCells

In the myocardial cells there is a In the myocardial cells there is a lengthening of the action potential lengthening of the action potential due to Ca due to Ca +2+2 entry entry

http://www.youtube.com/watch?v=OQpFFiLdE0E

APAP’’s in Contractile Myocardial s in Contractile Myocardial CellsCells

APAP’’s in Contractile Myocardial s in Contractile Myocardial CellsCells

Phase 4: Resting Membrane Potential is -90mVPhase 4: Resting Membrane Potential is -90mV Phase 0: Depolarization moves through gap Phase 0: Depolarization moves through gap

junctionsjunctions Membrane potential reaches +20mVMembrane potential reaches +20mV

Phase 1: Initial RepolarizationPhase 1: Initial Repolarization NaNa++ channels close; K channels close; K ++ channels open channels open

Phase 2: PlateauPhase 2: Plateau Repolarization flattens into a plateau due toRepolarization flattens into a plateau due to

A decrease in K A decrease in K ++ permeability and an permeability and an increase in Ca increase in Ca +2+2 permeability permeability

Voltage regulated Ca Voltage regulated Ca +2+2 channels channels activated by depolarization have been activated by depolarization have been slowly opening during phases 0 and 1slowly opening during phases 0 and 1

When they finally open, Ca When they finally open, Ca +2+2 enter the enter the cellcell

At the same time K At the same time K ++ channels close channels close This lengthens contraction of the cellsThis lengthens contraction of the cells AP = 200mSec or moreAP = 200mSec or more

Phase 3: Rapid RepolarizationPhase 3: Rapid Repolarization Plateau ends when Ca Plateau ends when Ca +2+2 gates close and K gates close and K ++

permeability increases againpermeability increases again

Myocardial Autorhythmic Myocardial Autorhythmic CellsCells

Myocardial Autorhythmic Myocardial Autorhythmic CellsCells

Anatomically distinct from Anatomically distinct from contractile cells – Also called contractile cells – Also called pacemakerpacemaker cells cells

Membrane Potential = – 60 Membrane Potential = – 60 mVmV

Spontaneous AP generation Spontaneous AP generation as gradual depolarization as gradual depolarization reaches thresholdreaches threshold

Unstable resting Unstable resting membrane potential (= membrane potential (= pacemaker potential)pacemaker potential)

The cell membranes are The cell membranes are ““leakyleaky””

Unique membrane Unique membrane channels that are channels that are permeable to both Napermeable to both Na++ and and KK++

Myocardial Autorhythmic Cells, Myocardial Autorhythmic Cells, contcont’’d.d.

I Iff-channel Causes Mem. Pot. -channel Causes Mem. Pot. InstabilityInstability

Myocardial Autorhythmic Cells, Myocardial Autorhythmic Cells, contcont’’d.d.

I Iff-channel Causes Mem. Pot. -channel Causes Mem. Pot. InstabilityInstability Autorhythmic cells have different Autorhythmic cells have different

membrane channel: membrane channel: IIff -- channelchannel

IIff channels let K channels let K++ & Na & Na++ through at - through at -60mV60mV

NaNa++ influx > K influx > K++ efflux efflux Slow depolarization to thresholdSlow depolarization to threshold

allow current(= I ) to flow

f = “funny”:researchers didn’tunderstand initially

Myocardial Autorhythmic Cells, Myocardial Autorhythmic Cells, contcont’’d.d.

““Pacemaker potentialPacemaker potential”” starts at ~ -60mV, starts at ~ -60mV, slowly drifts to slowly drifts to thresholdthreshold

APAP

Channels involved in APs of Cardiac Channels involved in APs of Cardiac Autorhythmic CellsAutorhythmic Cells

Slow depolarization due to Slow depolarization due to IIff channelschannels

As cell slowly depolarizes: IAs cell slowly depolarizes: Iff - -channels close & channels close & CaCa2+2+ channels channels start start openingopening

At threshold: lots of CaAt threshold: lots of Ca2+2+ channels channels open open AP to + 20mV AP to + 20mV

Repolarization due to efflux of KRepolarization due to efflux of K++

Myocardial Autorhythmic Cells, cont’d.

Autorhythmic CellsAutorhythmic Cells No nervous system input neededNo nervous system input needed Unstable membrane potentialUnstable membrane potential

-60mV Ca -60mV Ca +2+2 channels open channels open Calcium influx creates the steep depolarization Calcium influx creates the steep depolarization

phase of the action potentialphase of the action potential At the peak of the action potential Ca At the peak of the action potential Ca +2+2 channels channels

close and slow Kclose and slow K++ channels open channels open Repolarization of the autorhythmic action potential is Repolarization of the autorhythmic action potential is

due to the efflux of K due to the efflux of K ++ Pacemaker potential not called resting membrane Pacemaker potential not called resting membrane

potentialpotential At -60mV IAt -60mV Iff (funny) channels permeable to K (funny) channels permeable to K ++ and Na and Na ++

openopen Na Na ++ influx exceed K influx exceed K ++ efflux efflux

The net influx of positive charge slowly depolarizes the The net influx of positive charge slowly depolarizes the autorhythmic cellsautorhythmic cells

As the membrane becomes more positive the IAs the membrane becomes more positive the I ff channels gradually close and some Ca channels gradually close and some Ca +2+2 channels open channels open

The influx of Ca The influx of Ca +2+2 continues the depolarization until continues the depolarization until the membrane reaches thresholdthe membrane reaches threshold

http://www.youtube.com/watch?v=3HvIKsQb6es

Autonomic Autonomic Neurotransmitters Neurotransmitters

Modulate Heart RateModulate Heart Rate The speed at which pacemaker cells The speed at which pacemaker cells

depolarize determines the rate at which the depolarize determines the rate at which the heart contractsheart contracts

The interval between action potentials can be The interval between action potentials can be altered by changing the permeability of the altered by changing the permeability of the autorhythmic cells to different ionsautorhythmic cells to different ions Increase Na Increase Na ++ and Ca and Ca +2+2 permeability speeds up permeability speeds up

depolarization and heart ratedepolarization and heart rate Decrease Ca Decrease Ca +2+2 permeability or increase K permeability or increase K ++

permeability slow depolarization and slows heart permeability slow depolarization and slows heart raterate

http://www.youtube.com/watch?v=OQpFFiLdE0Ehttp://www.youtube.com/watch?v=OQpFFiLdE0E http://www.youtube.com/watch?v=j2iY1cT2gEEhttp://www.youtube.com/watch?v=j2iY1cT2gEE

Autonomic Autonomic Neurotransmitters Neurotransmitters

Modulate Heart RateModulate Heart Rate

The Catecholamines:The Catecholamines: norepi and epi norepi and epi increases ion flow through increases ion flow through IIff and and CaCa+2+2 channels channels More rapid cation entry speeds up the More rapid cation entry speeds up the

rate of the pacemaker depolarizationrate of the pacemaker depolarization ΒΒ1-adrenergic receptors are on 1-adrenergic receptors are on

autorhythmic cellsautorhythmic cells cAMP second messenger system causes cAMP second messenger system causes IIff

channels to remain open longerchannels to remain open longerhttp://www.youtube.com/watch?v=3HvIKsQb6es

Autonomic Autonomic Neurotransmitters Neurotransmitters

Modulate Heart RateModulate Heart Rate Parasympathetic neurotransmitter Parasympathetic neurotransmitter

(Acetylcholine) slows heart rate(Acetylcholine) slows heart rate Ach activates muscarinic cholinergic Ach activates muscarinic cholinergic

receptors that receptors that Increase KIncrease K++ permeability and permeability and Decrease CaDecrease Ca+2+2 permeability permeability

Electrical Conduction in the Electrical Conduction in the Heart Coordinates Heart Coordinates

ContractionContraction Action potential in an autorhythmic cellAction potential in an autorhythmic cell Depolarization spread rapidly to adjacent Depolarization spread rapidly to adjacent

cells through gap junctionscells through gap junctions Depolarization wave is followed by a wave of Depolarization wave is followed by a wave of

contraction across the atria from the contraction across the atria from the sinoatrial node on the right side of the heart sinoatrial node on the right side of the heart across to the left side of the heart and then across to the left side of the heart and then from the base to the apexfrom the base to the apex

From AV nodes to the atrioventricular From AV nodes to the atrioventricular bundle in the septum (Bundle of His)bundle in the septum (Bundle of His)

Left and right bundle branches to the apexLeft and right bundle branches to the apex Purkinje Fibers through the ventricles Purkinje Fibers through the ventricles

branches from apex to base and stopping at branches from apex to base and stopping at the atrioventricular septumthe atrioventricular septum

Pacemakers Set the Heart Pacemakers Set the Heart RateRate

SA Node is the fastest pacemakerSA Node is the fastest pacemaker Approximately 72 bpmApproximately 72 bpm

AV node approximately 50 bpmAV node approximately 50 bpm Bundle Branch BlockBundle Branch Block Complete Heart BlockComplete Heart Block

ElectrocardiogramElectrocardiogram

EinthovenEinthoven’’s triangles triangle Electrodes are attached to both arms and left Electrodes are attached to both arms and left

leg to form a triangleleg to form a triangle Lead I- negative electrode attached to Lead I- negative electrode attached to

right armright arm Lead II – positive electrode attached to Lead II – positive electrode attached to

left armleft arm Lead III – Ground attached to the left legLead III – Ground attached to the left leg

Electrocardiogram ECG Electrocardiogram ECG (EKG)(EKG)

• Surface electrodes record electrical activity Surface electrodes record electrical activity deep within body - deep within body - How possible?How possible?

• Reflects electrical activity of whole heart not Reflects electrical activity of whole heart not of single cell!of single cell!

• EC fluid = EC fluid = ““salt solutionsalt solution”” (NaCl) (NaCl) good good conductor of electricity to skin surfaceconductor of electricity to skin surface

• Signal very weak by time it gets to skinSignal very weak by time it gets to skin ventricular AP = ? mVventricular AP = ? mV ECG signal amplitude = 1mVECG signal amplitude = 1mV

EKG tracingEKG tracing = = of all electrical potentials of all electrical potentials generated by all cells of heart at any given generated by all cells of heart at any given momentmoment

ECGECG

P waveP wave Depolarization of the atriaDepolarization of the atria

Atrial contraction begins almost at the end of the P Atrial contraction begins almost at the end of the P wavewave

QRS complexQRS complex Ventricular depolarizationVentricular depolarization

Ventricular contraction begins just after the Q wave Ventricular contraction begins just after the Q wave and continues through the T waveand continues through the T wave

T waveT wave Ventricular repolarizationVentricular repolarization

ECGECG PQ or PR segmentPQ or PR segment

Conduction through AV node and AV bundleConduction through AV node and AV bundle Q waveQ wave

Conduction through bundle branchesConduction through bundle branches R waveR wave

Conduction beginning up the Purkinje FibersConduction beginning up the Purkinje Fibers S wave Conduction continue up half wayS wave Conduction continue up half way ST segmentST segment

Conduction up the second half of VentriclesConduction up the second half of Ventricles

ECGECG

When an electrical wave moving When an electrical wave moving through the heart is directed toward through the heart is directed toward the positive electrode, the ECG the positive electrode, the ECG waves goes up from the baselinewaves goes up from the baseline

If net charge movement through the If net charge movement through the heart is toward the negative heart is toward the negative electrode, the wave points electrode, the wave points downwarddownward

RARA LALA

LLLL

II

IIII IIIIII

– +

+

––

+

EinthovenEinthoven’’s Triangle and the 3 Limb s Triangle and the 3 Limb Leads:Leads:

Net electrical currentNet electrical currentin heart moves in heart moves

towards towards

++ electrode electrode

EKG tracing goesEKG tracing goesupup from baseline from baseline

Net electrical Net electrical current in current in

heart moves towards heart moves towards

-- electrodeelectrode

EKG tracing goesEKG tracing goesDown Down from from

baselinebaseline

Why neg. tracing for depolarization ??

Info provided by EKG:Info provided by EKG:Info provided by EKG:Info provided by EKG:

1.1. HRHR

2.2. RhythmRhythm

3.3. Relationships of EKG componentsRelationships of EKG components each P wave followed by QRS complex?each P wave followed by QRS complex? PR segment constant in length? etc. PR segment constant in length? etc.

etc.etc.

For the Expert:For the Expert:

Find subtle changes in shape or Find subtle changes in shape or duration of various waves or duration of various waves or segments.segments.

Indicates for example:Indicates for example: Change in conduction velocityChange in conduction velocity Enlargement of heartEnlargement of heart Tissue damage due to ischemia Tissue damage due to ischemia

(infarct!)(infarct!)

Prolonged QRS complexProlonged QRS complex

Injury to AV bundle can increase duration of Injury to AV bundle can increase duration of QRS complex (takes longer for impulse to QRS complex (takes longer for impulse to spread throughout ventricular walls).spread throughout ventricular walls).

1st HS: 1st HS: during early ventricular contraction during early ventricular contraction AV AV valves closevalves close

2nd HS:2nd HS: during early ventricular relaxation during early ventricular relaxation semilunar valves closesemilunar valves close

Heart Sounds (HS)Heart Sounds (HS)

Gallops, Clicks and Gallops, Clicks and MurmursMurmurs

Gallops, Clicks and Gallops, Clicks and MurmursMurmurs

Turbulent blood flow produces Turbulent blood flow produces heart murmurs upon heart murmurs upon auscultationauscultation

Plumbing 101:Plumbing 101:

ResistanceResistance Opposes Flow Opposes FlowPlumbing 101:Plumbing 101:

ResistanceResistance Opposes Flow Opposes Flow

3 parameters determine 3 parameters determine resistance (R)resistance (R)::

1.1. Tube length (L)Tube length (L)

1.1. Constant in bodyConstant in body

2.2. Tube radius (r)Tube radius (r)1.1. Can radius change?Can radius change?

3.3. Fluid viscosity Fluid viscosity (((eta))(eta))

1.1. Can blood viscosity Can blood viscosity change??change??

R =R =rr44

88L L

Poiseuille’s law

Blood Flow Rate Blood Flow Rate P/ RP/ R R R 1 / r1 / r44

Velocity (v) of Velocity (v) of FlowFlow

Depends on Flow Rate and Cross-Depends on Flow Rate and Cross-Sectional Area:Sectional Area:

Flow rate (Q)Flow rate (Q) = volume of blood = volume of blood passing one point in the system passing one point in the system per unit of time (e.g., ml/min)per unit of time (e.g., ml/min) If flow rate If flow rate velocity velocity

Cross-Sectional area (A)Cross-Sectional area (A) (or tube (or tube diameter)diameter) If cross sectional area If cross sectional area velocity velocity

v = Q / A

Blood FlowBlood Flow

Mechanistic:Mechanistic: Because the Because the contractions of the heart produce a contractions of the heart produce a hydrostatic pressure gradienthydrostatic pressure gradient and the and the blood wants to flow to the region of blood wants to flow to the region of lesser pressure. Therefore, the lesser pressure. Therefore, the Pressure gradient (Pressure gradient (P)P) is main driving is main driving force for flow through the vesselsforce for flow through the vessels

Blood Flow Rate Blood Flow Rate P/ RP/ R

PressurePressure Hydrostatic pressure is in all Hydrostatic pressure is in all

directionsdirections

Measured in mmHg: The Measured in mmHg: The pressure to raise a 1 cm pressure to raise a 1 cm column of Hg 1 mmcolumn of Hg 1 mm

SphygmomanometerSphygmomanometer

Flow is produce by Driving Flow is produce by Driving PressurePressure

Pressure of fluid in motion Pressure of fluid in motion decreases over distance because decreases over distance because of energy loss due to frictionof energy loss due to friction

Blood Flow Rate Blood Flow Rate P/ RP/ R

Unique Microanatomy of Unique Microanatomy of Cardiac Muscle CellsCardiac Muscle Cells

Unique Microanatomy of Unique Microanatomy of Cardiac Muscle CellsCardiac Muscle Cells

1% of cardiac cells are 1% of cardiac cells are autorhythmicautorhythmic

Signal to contract is myogenicSignal to contract is myogenic

Intercalated discs with gap Intercalated discs with gap junctions and desmosomesjunctions and desmosomes

Electrical link and strengthElectrical link and strength

SR smaller than in skeletal muscleSR smaller than in skeletal muscle

Extracelllar CaExtracelllar Ca2+2+ initiates initiates contraction (like smooth muscle)contraction (like smooth muscle)

Abundant mitochondria extract Abundant mitochondria extract about 80% of Oabout 80% of O22

Cardiac Muscle Cell Cardiac Muscle Cell Contraction is GradedContraction is GradedCardiac Muscle Cell Cardiac Muscle Cell

Contraction is GradedContraction is Graded

Skeletal muscle cell:Skeletal muscle cell: all-or-none all-or-none contractioncontraction in any single fiber for a given fiber in any single fiber for a given fiber length.length. Graded contraction in skeletal muscle Graded contraction in skeletal muscle occurs through?occurs through?

Cardiac muscle:Cardiac muscle: force force to sarcomere length to sarcomere length (up to a (up to a

maximum)maximum)

force force to # of Ca to # of Ca2+2+ activated activated crossbridgescrossbridges (Function of intracellular (Function of intracellular CaCa2+2+: if [Ca: if [Ca2+2+]]inin

low low not all not all

crossbridges activated)crossbridges activated)

http://www.youtube.com/watch?v=OQpFFiLdE0Ehttp://www.youtube.com/watch?v=j2iY1cT2gEE

http://www.youtube.com/watch?v=j2iY1cT2gEE

Length Tension RelationshipLength Tension Relationship

In order to increase In order to increase heart rate at the SA nodeheart rate at the SA node

A.A. Potassium permeability across the Potassium permeability across the membrane must increasemembrane must increase

B.B. Sodium permeability across the Sodium permeability across the membrane must increasemembrane must increase

C.C. Potassium impermeability across the Potassium impermeability across the membrane must increasemembrane must increase

D.D. Sodium impermeability across the Sodium impermeability across the membrane must increasemembrane must increase

The neurotransmitter The neurotransmitter responsible for increasing responsible for increasing

potassium permeability at the potassium permeability at the SA node isSA node is

A.A. NorepinephrineNorepinephrine

B.B. EpinephrineEpinephrine

C.C. AcetylcholineAcetylcholine

D.D. SerotoninSerotonin

The initiation of the The initiation of the heartbeat normally heartbeat normally originates from theoriginates from the

A.A. Atrio-ventricular (A-V) node of the Atrio-ventricular (A-V) node of the heartheart

B.B. Sino-atrial (SA) node of the heartSino-atrial (SA) node of the heart

C.C. Central nervous systemCentral nervous system

D.D. ThyroidThyroid

The systemic circulationThe systemic circulation

A.A. Receives more blood than the Receives more blood than the pulmonary circulation doespulmonary circulation does

B.B. Receives blood from the left Receives blood from the left ventricleventricle

C.C. Is a high pressure system compared Is a high pressure system compared to the pulmonary circulationto the pulmonary circulation

D.D. Both (b) and (c) above are correctBoth (b) and (c) above are correct

E.E. All of the above are correctAll of the above are correct

The chordae tendinaeThe chordae tendinae

A.A. KKeep the AV valves from opening in eep the AV valves from opening in the opposite direction during the opposite direction during ventricular contractionventricular contraction

B.B. Hold the AV valves during diastoleHold the AV valves during diastole

C.C. Hold the right and left ventricles Hold the right and left ventricles togethertogether

D.D. Transmit the electrical impulse form Transmit the electrical impulse form the atria to the ventriclesthe atria to the ventricles

E.E. Contract when the ventricles contractContract when the ventricles contract

The aortic valve prevents backflow The aortic valve prevents backflow of blood from the aorta into the of blood from the aorta into the left ventricle during ventricular left ventricle during ventricular

diastolediastoleA.A. TrueTrue

B.B. FalseFalse

A mammalian heart has A mammalian heart has __________ chamber(s)__________ chamber(s)

A.A. OneOne

B.B. TwoTwo

C.C. ThreeThree

D.D. FourFour

Ectopic focus is the place Ectopic focus is the place wherewhere

A.A. AAn abnormally excitable area of the n abnormally excitable area of the heart initiates a premature action heart initiates a premature action potentialpotential

B.B. All of the electrical impulses of the All of the electrical impulses of the heart normally terminateheart normally terminate

C.C. An ECG lead is attached on the outside An ECG lead is attached on the outside of the chestof the chest

D.D. A heart valve is attachedA heart valve is attached

E.E. The chordae tendineae attach to a valveThe chordae tendineae attach to a valve

During isovolumetric ventricular During isovolumetric ventricular contractioncontraction

A.A. RRapid filling of the ventricles occursapid filling of the ventricles occurs

B.B. No blood enters or leaves the No blood enters or leaves the ventriclesventricles

C.C. The maximum volume of blood is The maximum volume of blood is ejectedejected

D.D. The maximum rate of ejection The maximum rate of ejection occursoccurs

E.E. None of the above is correctNone of the above is correct

The type of intercellular junction The type of intercellular junction that connects cardiac muscle that connects cardiac muscle fibers and allows for direct, fibers and allows for direct,

electrical synapsing is known as aelectrical synapsing is known as aA.A. Tight junctionTight junction

B.B. DesmosomeDesmosome

C.C. PlasmodesmataPlasmodesmata

D.D. Gap junctionGap junction

Cardiac muscleCardiac muscle

A.A. Has a shortening velocity that is Has a shortening velocity that is greater than that of glycolytic (white) greater than that of glycolytic (white) skeletal muscle fibersskeletal muscle fibers

B.B. Has a more extensive sarcoplasmic Has a more extensive sarcoplasmic reticulum than skeletal musclereticulum than skeletal muscle

C.C. Is an electrical syncytiumIs an electrical syncytium

D.D. Has a resting potential that depends Has a resting potential that depends mainly on sodium distributionmainly on sodium distribution

E.E. All of the above are correctAll of the above are correct

Spontaneous Spontaneous depolarization of the depolarization of the

sinoatrial node is sinoatrial node is produced byproduced byA.A. An inward leak of sodium and an increase An inward leak of sodium and an increase

in the outward leak of potassiumin the outward leak of potassium

B.B. An inward leak of sodium and a decrease An inward leak of sodium and a decrease in the outward leak of potassiumin the outward leak of potassium

C.C. Opening of fast sodium channels and a Opening of fast sodium channels and a decrease in the outward leak of potassiumdecrease in the outward leak of potassium

D.D. Opening of fast sodium channels and an Opening of fast sodium channels and an increase in the outward leak of potassiumincrease in the outward leak of potassium

E.E. Neural impulses from the sympathetic Neural impulses from the sympathetic nervesnerves

A heart murmur is A heart murmur is characterized bycharacterized by

A.A. Rapid heart contractionRapid heart contraction

B.B. Irregular heart contractionIrregular heart contraction

C.C. Mitral valve prolapseMitral valve prolapse

D.D. Semilunar valve dysfunctionSemilunar valve dysfunction

The P wave of a normal The P wave of a normal electrocardiogram electrocardiogram

indicatesindicatesA.A. Atrial depolarizationAtrial depolarization

B.B. Ventricular depolarizationVentricular depolarization

C.C. Atrial repolarizationAtrial repolarization

D.D. Ventricular repolarizationVentricular repolarization

Damage to the _______ is Damage to the _______ is referred to as heart referred to as heart

blockblockA.A. SA nodeSA node

B.B. AV nodeAV node

C.C. AV bundle AV bundle

D.D. AV valveAV valve

Stenosis of the mitral valve may Stenosis of the mitral valve may initially cause a pressure increase initially cause a pressure increase

in thein theA.A. Vena cavaVena cava

B.B. Pulmonary circulationPulmonary circulation

C.C. Left ventricleLeft ventricle

D.D. Coronary circulationCoronary circulation

The tricuspid valve is The tricuspid valve is closedclosed

A.A. While the ventricle is in diastoleWhile the ventricle is in diastole

B.B. By the movement of blood from By the movement of blood from the atrium to ventriclethe atrium to ventricle

C.C. By the movement of blood from By the movement of blood from atrium to ventricleatrium to ventricle

D.D. While the atrium is contractingWhile the atrium is contracting

E.E. When the ventricle is in systoleWhen the ventricle is in systole