Cardio physiology

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Heart felt facts Heart felt facts The average adult heart beats 72 times a The average adult heart beats 72 times a minute; 100,000 times a day and 2.5 minute; 100,000 times a day and 2.5 billion times during a lifetime billion times during a lifetime Though weighing only 11 ounces on average, Though weighing only 11 ounces on average, a healthy heart pumps 2,000 gallons of a healthy heart pumps 2,000 gallons of blood through 60,000 miles of blood blood through 60,000 miles of blood vessels each day. vessels each day. A kitchen faucet would need to be turned A kitchen faucet would need to be turned on all the way for at least 45 years to on all the way for at least 45 years to equal the amount of blood pumped by the equal the amount of blood pumped by the heart in an average lifetime heart in an average lifetime

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Cardio physiology

Transcript of Cardio physiology

Page 1: Cardio physiology

Heart felt factsHeart felt facts The average adult heart beats 72 times a minute; The average adult heart beats 72 times a minute;

100,000 times a day and 2.5 billion times during 100,000 times a day and 2.5 billion times during a lifetimea lifetime

Though weighing only 11 ounces on average, a Though weighing only 11 ounces on average, a healthy heart pumps 2,000 gallons of blood healthy heart pumps 2,000 gallons of blood through 60,000 miles of blood vessels each day.through 60,000 miles of blood vessels each day.

A kitchen faucet would need to be turned on all A kitchen faucet would need to be turned on all the way for at least 45 years to equal the amount the way for at least 45 years to equal the amount of blood pumped by the heart in an average of blood pumped by the heart in an average lifetimelifetime

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Heart felt factsHeart felt facts The heart begins beating at four The heart begins beating at four

weeks after conception and does not weeks after conception and does not stop until death.stop until death.

Early Egyptians believed that the Early Egyptians believed that the heart and other major organs had heart and other major organs had wills of their own and would move wills of their own and would move around inside the body.around inside the body.dd

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Heart felt factsHeart felt facts Plato theorized that reasoning Plato theorized that reasoning

originated with the brain, but that originated with the brain, but that passions originated in the “fiery” passions originated in the “fiery” heartheart

Physician Erasistratus of Chios (304-Physician Erasistratus of Chios (304-250 B.C.) was the first to discover 250 B.C.) was the first to discover that the heart functioned as a natural that the heart functioned as a natural pumppump

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Heart felt factsHeart felt facts In his text In his text De Humani Corporis Fabrica Libri De Humani Corporis Fabrica Libri

SeptemSeptem, the father of modern anatomy, , the father of modern anatomy, Andreas Vesalius (1514-1564), argued that the Andreas Vesalius (1514-1564), argued that the blood seeped from one ventricle to another blood seeped from one ventricle to another through mysterious pores.through mysterious pores.ff

Galen argued that the heart constantly Galen argued that the heart constantly produced blood. However, William Harvey’s produced blood. However, William Harvey’s (1578-1657) discovery of the circulation (1578-1657) discovery of the circulation system in 1616 revealed that there was a system in 1616 revealed that there was a finite amount of blood in the body and that it finite amount of blood in the body and that it circulated in one directioncirculated in one direction

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Heart felt factsHeart felt facts Every day, the heart creates enough Every day, the heart creates enough

energy to drive a truck 20 miles. In a energy to drive a truck 20 miles. In a lifetime, that is equivalent to driving lifetime, that is equivalent to driving to the moon and back.to the moon and back.aa

Because the heart has its own Because the heart has its own electrical impulse, it can continue to electrical impulse, it can continue to beat even when separated from the beat even when separated from the body, as long as it has an adequate body, as long as it has an adequate supply of oxygen.supply of oxygen.

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Heart felt factsHeart felt facts In 1903, physiologist Willem Einthoven (1860-1927) In 1903, physiologist Willem Einthoven (1860-1927)

invented the electrocardiograph, which measures electric invented the electrocardiograph, which measures electric current in the heart.current in the heart.

Atrium” is Latin for “entrance hall,” and “ventricle” is Latin Atrium” is Latin for “entrance hall,” and “ventricle” is Latin for “little belly.for “little belly.

Galen agreed with Aristotle that the heart was the body’s Galen agreed with Aristotle that the heart was the body’s source of heat, a type of “lamp” fueled by blood from the source of heat, a type of “lamp” fueled by blood from the liver and fanned into spirituous flame by air from the lungs. liver and fanned into spirituous flame by air from the lungs. The brain merely served to cool the blood.The brain merely served to cool the blood.

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Location of the HeartLocation of the Heart The heart is located between the The heart is located between the

lungs behind the sternum and above lungs behind the sternum and above the diaphragm.the diaphragm.

It is surrounded by the pericardium.It is surrounded by the pericardium. Its size is about that of a fist, and its Its size is about that of a fist, and its

weight is about 250-300 g.weight is about 250-300 g. Its center is located about 1.5 cm to Its center is located about 1.5 cm to

the left of the midsagittal plane. the left of the midsagittal plane.

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Location of the heart in the thoraxLocation of the heart in the thorax

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What is a Heart?What is a Heart?

The heart is composed of The heart is composed of contractile muscle, similar to contractile muscle, similar to our skeletal muscle.our skeletal muscle.

The heart acts as a pump for The heart acts as a pump for our bodies’ blood supply.our bodies’ blood supply.

– Blood is pumped to the Blood is pumped to the lungs via the right ventricle lungs via the right ventricle to pick up oxygen.to pick up oxygen.

– Blood is pumped to the Blood is pumped to the tissue via the left ventricle tissue via the left ventricle to distribute oxygen to distribute oxygen throughout the body.throughout the body.

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Basic Heart Anatomy

• Heart consists of 4 chambers (2 atria & 2 ventricles).

• Atria are smaller than ventricles, left ventricle bigger than right ventricle.

• Blood flows in the following order: 1. Right atria2. Right ventricle3. Lungs4. Left atria5. Left ventricle6. Rest of Body

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Blood circulation via Blood circulation via hhearteart• The blood returns from the systemic circulation to the right atrium and from there goes through the tricuspid valve to the right ventricle.

• It is ejected from the right ventricle through the pulmonary valve to the lungs.

• Oxygenated blood returns from the lungs to the left atrium, and from there through the mitral valve to the left ventricle.

• Finally blood is pumped through the aortic valve to the aorta and the systemic circulation..

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The Heart Valves The Heart Valves TheThe tricuspid valve tricuspid valve regulates blood regulates blood

flow between the right atrium and flow between the right atrium and right ventricle.right ventricle.

TheThe pulmonary valve pulmonary valve controls blood controls blood flow from the right ventricle into the flow from the right ventricle into the pulmonary arteriespulmonary arteries

The The mitralmitral valvevalve lets oxygen-rich lets oxygen-rich blood from your lungs pass from the blood from your lungs pass from the left atrium into the left ventricle.left atrium into the left ventricle.

The The aortic valveaortic valve lets oxygen-rich lets oxygen-rich blood pass from the left ventricle blood pass from the left ventricle into the aorta, then to the bodyinto the aorta, then to the body

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What is an Action Potential?What is an Action Potential?

Normally, our cells maintain a Normally, our cells maintain a membrane potential of -55mV. membrane potential of -55mV.

During an During an action potentialaction potential, , the membrane potential the membrane potential quickly reaches +5mV for a quickly reaches +5mV for a short time.short time.

The large spike in membrane The large spike in membrane potential is due to an influx of potential is due to an influx of positive Napositive Na++ and Ca and Ca2+ 2+ ions. ions.

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What Causes a Heart Contraction?What Causes a Heart Contraction?

There are several areas of the heart that rhythmically fire There are several areas of the heart that rhythmically fire action potentialsaction potentials generating a wave of electrical energy. This electrical signal is what causes the generating a wave of electrical energy. This electrical signal is what causes the heart muscles to contract. heart muscles to contract.

The The S-A nodeS-A node depolarizes at the fastest rate and is therefore the depolarizes at the fastest rate and is therefore the pacemakerpacemaker for for the heart. The rest of the nodes transfer the electrical signal of the SA-node to the the heart. The rest of the nodes transfer the electrical signal of the SA-node to the other chambers of the heart, stimulating them to contract in turn. other chambers of the heart, stimulating them to contract in turn.

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Electrocardiograms (ECGs)Electrocardiograms (ECGs) Because a large number of Because a large number of

cells in the heart rhythmically cells in the heart rhythmically depolarize, with each depolarize, with each contraction, we can record contraction, we can record the electrical changes on our the electrical changes on our body surface. body surface.

This electrical trace is known This electrical trace is known as an as an electrocardiogramelectrocardiogram. .

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Electrocardiogram and Heart RateElectrocardiogram and Heart Rate

1.1. The The SA-nodeSA-node is the first is the first part of the heart to show part of the heart to show electrical activity. electrical activity.

ECG

Heart

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Electrocardiogram and Heart RateElectrocardiogram and Heart Rate

2.2. Shortly after the Shortly after the SA-nodeSA-node fires, both atria of the heart fires, both atria of the heart depolarize (depolarize (P-waveP-wave) ) followed closely by atrial followed closely by atrial contraction. contraction.

ECG

Heart

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Electrocardiogram and Heart RateElectrocardiogram and Heart Rate

3.3. There is a brief pause, and There is a brief pause, and then the then the AV-nodeAV-node, Bundle , Bundle of HIS, and Purkinje fibers of HIS, and Purkinje fibers fire in succession (QRS fire in succession (QRS complex). complex).

ECG

Heart

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Electrocardiogram and Heart RateElectrocardiogram and Heart Rate

3.3. There is a brief pause, and There is a brief pause, and then the AV-node, then the AV-node, Bundle Bundle of HISof HIS, and Purkinje fibers , and Purkinje fibers fire in succession (QRS fire in succession (QRS complex). complex).

ECG

Heart

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Electrocardiogram and Heart RateElectrocardiogram and Heart Rate

3.3. There is a brief pause, and There is a brief pause, and then the AV-node, Bundle of then the AV-node, Bundle of HIS, and HIS, and Purkinje fibersPurkinje fibers fire in succession (QRS fire in succession (QRS complex). complex).

ECG

Heart

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Electrocardiogram and Heart RateElectrocardiogram and Heart Rate

3.3. There is a brief pause, and There is a brief pause, and then the AV-node, Bundle of then the AV-node, Bundle of HIS, and Purkinje fibers fire HIS, and Purkinje fibers fire in succession (in succession (QRS QRS complexcomplex). ).

ECG

Heart

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Electrocardiogram and Heart RateElectrocardiogram and Heart Rate

4.4. Following Ventricular Following Ventricular depolarization, the depolarization, the ventricles contract and ventricles contract and repolarization (repolarization (T-waveT-wave) ) occurs. occurs.

ECG

Heart

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How Does the Electrical Signal Travel How Does the Electrical Signal Travel Throughout the Heart?Throughout the Heart?

The electrical signal from The electrical signal from pacemaker cells spreads to pacemaker cells spreads to nearby cells via nearby cells via gap gap junctionsjunctions..

Gap junctionsGap junctions are channels are channels that are shared by two that are shared by two adjacent cell membranes. adjacent cell membranes.

When one heart cell fires an When one heart cell fires an electrical signal, the signal electrical signal, the signal quickly spreads to neighboring quickly spreads to neighboring cells. cells.

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MAIN FUNCTIONS OF THE MAIN FUNCTIONS OF THE CIRCULATORY SYSTEMCIRCULATORY SYSTEM

Transport and distribute essential Transport and distribute essential substances to the tissues.substances to the tissues.

Remove metabolic byproducts.Remove metabolic byproducts. Adjustment of oxygen and nutrient Adjustment of oxygen and nutrient

supply in different physiologic states.supply in different physiologic states. Regulation of body temperature.Regulation of body temperature. Humoral communication.Humoral communication.

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Pressure Profile of the Circulatory Pressure Profile of the Circulatory SystemSystem

ELASTIC TISSUEMUSCLE

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Distribution of Blood in the Distribution of Blood in the Circulatory SystemCirculatory System

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THE CONDUCTION SYSTEM OF THE THE CONDUCTION SYSTEM OF THE HEARTHEART

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Electrical activation of the heart Electrical activation of the heart In the heart muscle cell, or In the heart muscle cell, or myocytemyocyte, ,

electric activation takes place by electric activation takes place by means of the same mechanism as in means of the same mechanism as in the nerve cell, i.e., from the inflow of the nerve cell, i.e., from the inflow of Na ions across the cell membrane.Na ions across the cell membrane.

The amplitude of the action potential The amplitude of the action potential is also similar, being 100 mV for both is also similar, being 100 mV for both nerve and muscle. nerve and muscle.

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The duration of the cardiac impulse is, The duration of the cardiac impulse is, however, two orders of magnitude however, two orders of magnitude longer than in either nerve cell or longer than in either nerve cell or sceletal muscle cell. sceletal muscle cell.

As in the nerve cell, repolarization is a As in the nerve cell, repolarization is a consequence of the outflow of K ions.consequence of the outflow of K ions.

The duration of the action impulse is The duration of the action impulse is about 300 ms.about 300 ms.

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Mechanical contraction Mechanical contraction of Cardiac Muscleof Cardiac Muscle

• Associated with the electric activation of cardiac muscle cell is its mechanical contraction, which occurs a little later.

• An important distinction between cardiac muscle tissue and skeletal muscle is that in cardiac muscle, activation can propagate from one cell to another in any direction.

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The Conduction SystemThe Conduction System Electrical signal begins in the sinoatrial Electrical signal begins in the sinoatrial

(SA) node: "natural pacemaker." (SA) node: "natural pacemaker." – causes the atria to contract. causes the atria to contract.

The signal then passes through the The signal then passes through the atrioventricular (AV) node. atrioventricular (AV) node. – sends the signal to the ventricles via sends the signal to the ventricles via

the “bundle of His” the “bundle of His” – causes the ventricles to contract. causes the ventricles to contract.

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The Conduction SystemThe Conduction System

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Conduction on the HeartConduction on the Heart• The sinoatrial node in humans is in the shape of a crescent and is about 15 mm long and 5 mm wide.

• The SA nodal cells are self-excitatory, pacemaker cells.

• They generate an action potential at the rate of about 70 per minute.

• From the sinus node, activation propagates throughout the atria, but cannot propagate directly across the boundary between atria and ventricles.

• The atrioventricular node (AV node) is located at the boundary between the atria and ventricles; it has an intrinsic frequency of about 50 pulses/min.

• If the AV node is triggered with a higher pulse frequency, it follows this higher frequency. In a normal heart, the AV node provides the only conducting path from the atria to the ventricles.

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• Propagation from the AV node to the ventricles is provided by a specialized conduction system.

Proximally, this system is composed of a common bundle, called the •bundle of His (after German physician Wilhelm His, Jr., 1863-1934).

• More distally, it separates into two bundle branches propagating along each side of the septum, constituting the right and left bundle branches. (The left bundle subsequently divides into an anterior and posterior branch.)

• Even more distally the bundles ramify into Purkinje fibers (named after Jan Evangelista Purkinje (Czech; 1787-1869)) that diverge to the inner sides of the ventricular walls.

• Propagation along the conduction system takes place at a relatively high speed once it is within the ventricular region, but prior to this (through the AV node) the velocity is extremely slow.

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• From the inner side of the ventricular wall, the many activation sites cause the formation of a wavefront which propagates through the ventricular mass toward the outer wall.

• This process results from cell-to-cell activation.

• After each ventricular muscle region has depolarized, repolarization occurs.

Propagation on ventricular wall

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Heart Physiology: Heart Physiology: Sequence of ExcitationSequence of Excitation

Sinoatrial (SA) nodeSinoatrial (SA) node generates impulses about 75 generates impulses about 75 times/minutetimes/minute

Atrioventricular (AV)Atrioventricular (AV) node delays the impulse node delays the impulse approximately 0.1 secondapproximately 0.1 second

ImpulseImpulse passes from atria to ventricles via the passes from atria to ventricles via the atrioventricular bundleatrioventricular bundle (bundle of His) (bundle of His)

AV bundleAV bundle splits into two pathways in the splits into two pathways in the interventricular septum (bundle branches)interventricular septum (bundle branches)– Bundle branchesBundle branches carry the impulse toward the carry the impulse toward the

apex of the heartapex of the heart– Purkinje fibersPurkinje fibers carry the impulse to the heart apex carry the impulse to the heart apex

and ventricular wallsand ventricular walls

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Extrinsic Innervation Extrinsic Innervation of the Heartof the Heart

Heart is Heart is stimulatedstimulated by the by the sympathetic sympathetic cardioacceleratory cardioacceleratory center center

Heart is Heart is inhibitedinhibited by the by the parasympathetic parasympathetic cardioinhibitory centercardioinhibitory center

Figure 18.15

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ElectrocardiographyElectrocardiography

Figure 18.16

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ElectrocardiographyElectrocardiography Electrical activity is recorded by electrocardiogram Electrical activity is recorded by electrocardiogram

(ECG)(ECG) P waveP wave corresponds to depolarization of corresponds to depolarization of SA nodeSA node QRS complexQRS complex corresponds to corresponds to ventricular ventricular

depolarizationdepolarization T waveT wave corresponds to corresponds to ventricular repolarizationventricular repolarization Atrial repolarizationAtrial repolarization record is masked by the record is masked by the

larger larger QRS complexQRS complex

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Electrocardiogram TracingsElectrocardiogram Tracings

Normal Sinus RhythmNormal Sinus Rhythm

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Electrocardiogram TracingsElectrocardiogram Tracings

Junctional Rhythm (Nodal Rhythm)Junctional Rhythm (Nodal Rhythm)– The The SA nodeSA node is nonfunctional is nonfunctional– P wavesP waves are absent are absent– Heart rate is paced by the Heart rate is paced by the AV node, AV node, 40-60 beats/min40-60 beats/min

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Electrocardiogram TracingsElectrocardiogram Tracings

Second Degree Heart BlockSecond Degree Heart Block– Some Some P wavesP waves are are NOTNOT conducted through the AV conducted through the AV

node consequently more node consequently more P wavesP waves than than QRS wavesQRS waves are present.are present.

– Ratio of P waves to QRS waves is 2:1Ratio of P waves to QRS waves is 2:1

PPPP

QRS QRSQRS

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Electrocardiogram TracingsElectrocardiogram Tracings

Figure 18.18

Ventricular FibrillationVentricular Fibrillation– Chaotic grossly irregular ECG deflections as Chaotic grossly irregular ECG deflections as

seen in seen in acute heart attackacute heart attack and and electrical electrical shockshock

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Mechanical Events of the Cardiac CycleMechanical Events of the Cardiac Cycle

Cardiac cycleCardiac cycle refers to all events associated with refers to all events associated with blood flow through the heart during one complete blood flow through the heart during one complete heartbeatheartbeatSystole –Systole – contractioncontraction of heart muscle of heart muscleDiastole Diastole – – relaxationrelaxation of heart muscleof heart muscle

Heart Beats ~ Heart Beats ~ 75 times per minute75 times per minuteComplete Cardiac Cycle = Complete Cardiac Cycle = 0.8 seconds0.8 secondsMechanical events always follow the electrical events Mechanical events always follow the electrical events

as seen in the ECGas seen in the ECG

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Sympathetic nervous systemSympathetic nervous system (SNS) stimulation (SNS) stimulation is activated by stress, anxiety, excitement, or is activated by stress, anxiety, excitement, or exercise exercise

Parasympathetic nervous systemParasympathetic nervous system (PNS) (PNS) stimulation is mediated by stimulation is mediated by acetylcholineacetylcholine and and opposes the SNS opposes the SNS

PNSPNS dominates the autonomic stimulation, dominates the autonomic stimulation, slowing heart rate and causing slowing heart rate and causing vagal tonevagal tone (inhibition of the heartbeat)(inhibition of the heartbeat)

Regulation of Heart Rate Regulation of Heart Rate Autonomic Nervous SystemAutonomic Nervous System

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Chemical Regulation of the HeartChemical Regulation of the Heart

The hormones The hormones epinephrineepinephrine and and thyroxinethyroxine increase heart rateincrease heart rate

Intracellular & extracellular ion concentrations Intracellular & extracellular ion concentrations must be maintained for normal heart functionmust be maintained for normal heart function

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SystoleSystole The heart in the systole phase. Systole, or contraction, of The heart in the systole phase. Systole, or contraction, of

the heart is initiated by the electrical cells of the sinoatrial the heart is initiated by the electrical cells of the sinoatrial node, which is the heart's natural pacemaker. These cells node, which is the heart's natural pacemaker. These cells are activated spontaneously by depolarization of their are activated spontaneously by depolarization of their membranes beyond a certain threshold for excitation. At membranes beyond a certain threshold for excitation. At this point, voltagegated calcium channels on the cell this point, voltagegated calcium channels on the cell membrane open and allow calcium ions to pass through, membrane open and allow calcium ions to pass through, into the sarcoplasm, or interior, of the muscle cell. Some into the sarcoplasm, or interior, of the muscle cell. Some calcium ions bind to receptors on the sarcoplasmic calcium ions bind to receptors on the sarcoplasmic reticulum causing an influx of calcium ions into the reticulum causing an influx of calcium ions into the sarcoplasm. sarcoplasm.

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SystoleSystole The calcium ions bind to the troponin, causing a The calcium ions bind to the troponin, causing a

conformation change, breaking the bond between the conformation change, breaking the bond between the protein tropomyosin, to which the troponin is attached, and protein tropomyosin, to which the troponin is attached, and the myosin binding sites. This allows the myosin heads to the myosin binding sites. This allows the myosin heads to bind to the myosin binding sites on the actin protein bind to the myosin binding sites on the actin protein filament and contraction results as the myosin heads draw filament and contraction results as the myosin heads draw the actin filaments along, are bound by ATP, causing them the actin filaments along, are bound by ATP, causing them to release the actin, and return to their original position, to release the actin, and return to their original position, breaking down the ATP into ADP and a phosphate group. breaking down the ATP into ADP and a phosphate group. The action potential spreads via the passage of sodium ions The action potential spreads via the passage of sodium ions through the gap junctions that connect the sarcoplasm of through the gap junctions that connect the sarcoplasm of adjacent myocardial cells.adjacent myocardial cells.

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SystoleSystole NorepinephrineNorepinephrine Beta1 adrenoreceptorsBeta1 adrenoreceptors G protein linked receptors conformational changeG protein linked receptors conformational change G protein involved in camp production from G protein involved in camp production from

ATP inturn activates protein kinaseATP inturn activates protein kinase ß-adrenoreceptor kinase phosphorylates the ß-adrenoreceptor kinase phosphorylates the

calcium ion channels in the sarcolemacalcium ion channels in the sarcolema More calcium more troponin bound more More calcium more troponin bound more

myosine sites free more powerful contractionmyosine sites free more powerful contraction

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Heart’s position in thoraxHeart’s position in thorax

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Heart’s position in thoraxHeart’s position in thorax In mediastinum – behind sternum and In mediastinum – behind sternum and

pointing left, lying on the diaphragmpointing left, lying on the diaphragm It weighs 250-350 gm (about 1 pound)It weighs 250-350 gm (about 1 pound)

Feel your heart beat at apex

(this is of a person lying down)

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Layers of the heart wallLayers of the heart wall

Muscle of the heart with inner and Muscle of the heart with inner and outer membrane coveringsouter membrane coverings

Muscle of heart = Muscle of heart = “myocardium”“myocardium” The layers from out to in:The layers from out to in:

– EpicardiumEpicardium = visceral layer of serous = visceral layer of serous pericardiumpericardium

– MyocardiumMyocardium = the muscle = the muscle– EndocardiumEndocardium lining the chambers lining the chambers

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ValvesValvesthree tricuspidthree tricuspidone bicuspidone bicuspid

““Tricuspid” valveTricuspid” valve– RA to RVRA to RV

Pulmonary or pulmonic valvePulmonary or pulmonic valve– RV to pulmonary trunk (branches R and L)RV to pulmonary trunk (branches R and L)

Mitral valve (the bicuspid one)Mitral valve (the bicuspid one)– LA to LVLA to LV

Aortic valveAortic valve– LV to aortaLV to aorta

(cusp means flap)

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Function of AV valves

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Function of semilunar valves(Aortic and pulmonic valves)

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In the fetus, the RA In the fetus, the RA received oxygenated received oxygenated blood from mom blood from mom through umbilical through umbilical cord, so blood R to L cord, so blood R to L through the through the foramen foramen ovale: ovale: fossa ovalis is fossa ovalis is left after it closesleft after it closes

The pulmonary trunk The pulmonary trunk had high resistance had high resistance (because lungs not (because lungs not functioning yet) & functioning yet) & ductus arteriosusductus arteriosus shunted blood to shunted blood to aorta; becomes aorta; becomes ligamentum ligamentum arteriosumarteriosum after birth after birth

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HeartbeatHeartbeat

Systole: contractionSystole: contraction Diastole: fillingDiastole: filling Normal rate: 60-100Normal rate: 60-100 Slow: bradycardiaSlow: bradycardia Fast: tachycardiaFast: tachycardia

***Note: blood goes to RA, then RV, then lungs, then LA, then LV, then body; but the fact that a given drop of blood passes through the heart chambers sequentially does not mean that the four chambers contract in that order; the 2 atria always contract together, followed by the simultaneous contraction of the 2 ventricles

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another flow chartanother flow chart

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• Heart Disease is the number one killer • 16.7 million deaths are result forms of cardiovascular disease, heart disease and stroke.

• Stress, birth control pills and alcohol are just some risk factors of developing heart disease.

• research suggests that taking a small dose of aspirin daily may help prevent a heart attack(because aspirin inhibits platelet clumping).

• The length of all your blood vessels lined up is about 60,000 miles long!

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Ways To A Healthy HeartWays To A Healthy Heart

• Eating healthy, good nutrition

• Fitness and Exercise

• Having a healthy lifestyle, don't smoke

• Watch cholesterol and blood pressure

• Reduce the fat, sodium, and calories in your diet.• The total length of capillaries in an average adult human is approximately 25,000 mi (42,000km).