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Cardiovascular PhysiologyCardiovascular Physiology

Cardiovascular SystemCardiovascular System

Purpose• Transport O2 to tissues and removal of waste• Transport of nutrients to tissues• Regulation of body temperature

Two Systems:• Pulmonary Circulation

Blood flow to, within, and from the lungs

• Systemic CirculationBlood flow to, within & from the remainder of the body

Right atrium

Superior vena cava

Right coronary artery

Right ventricle

Inferior vena cava

Aorta

Pulmonary trunk

Left atrium

Left ventricle

Heart Anatomy

Great cardiac vein

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Right pulmonary artery

Papillary muscle

Chordae tendineae

Myocardium

Pulmonary semilunarvalve

Left pulmonary artery

Heart Anatomy Heart Anatomy cont.cont.

Tricuspid valveBicuspid (Mitral) valve

Aortic semilunar valvenot pictured

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The Heart

Mitral valve

Pulmonaryveins

Pulmonary arteryAorta artery

Superior vena cava

Inferior vena cava

Tricuspid valve

Right ventricle

Left ventricle

Pulmonary Semilunar valve

Aortic valve

Pulmonary semilunarvalve

Tricuspid valve

Aortic semilunarvalve

Bicuspid (Mitral) valve

Figure 9.5 (1)Page 307

Figure 9.5 (1)Page 307

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Figure 9.4 Page 307Figure 9.4 Page 307

Valve opened

Valve closed; does not open in opposite direction

The Circulatory SystemThe Circulatory SystemHeart• Pumps blood

Arteries and arterioles• Carry blood away from the heart

Capillaries• Exchange of nutrients with tissues

Veins and venules• Carry blood toward the heart

Systemic & Pulmonary CircuitsSystemic & Pulmonary Circuits

Systemic circuit

• Left side of the heart

• Pumps oxygenated blood to the whole body via arteries

• Returns deoxygenated blood to the right heart via veins

Pulmonary circuit

• Right side of the heart

• Pumps deoxygenated blood to the lungs via pulmonary arteries

• Returns oxygenated blood to the left heart via pulmonary veins

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Arterioles VenulesPulmonary circulation

Systemic circulation

Venules Arterioles

Pulmonary capillaries

Pulmonary artery

Systemic veins

Systemic capillaries

Tissues

Smaller arteriesbranching offto supply various tissues

Aorta (major systemic artery)

Pulmonaryveins

Figure 10.4Page 346

Figure 10.4Page 346

Driving Pressures

Venae cavae Rightatrium

Right ventricle

Pulmonary artery

Other systemicorgans

Brain Digestivetract

Kidneys Muscles Systemiccirculation

Pulmonarycirculation Lungs

Leftventricle

LeftatriumAorta Pulmonary veins

Figure 9.3 (2)Page 306

Figure 9.3 (2)Page 306

Electrical Conduction System

Electrical Conduction System

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The MyocardiumThe Myocardium

Electrical Activity of the HeartElectrical Activity of the Heart

Cardiac muscle cells• Contractile (99%)• Autorhythmic

Pacemaker potential

Impulse is initiated in the right atrium and spreads throughout entire heart

May be recorded on an electrocardiogram (ECG)

Na+ equilibriumpotential

K+ equilibriumpotential

Thresholdpotential

Restingpotential

= Action potential = After hyperpolarization

Triggering event

Figure 4.6Page 103

Figure 4.6Page 103

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Pacemaker Potential (Autorhythmic Cells)Pacemaker Potential (Autorhythmic Cells)

1. Slow initial depolarization caused by:• Decrease in K+ leaving cell

Cardiac cells – membrane decreases in permeability to K+

between AP

• Slow, inward leak of Na+

No voltage gated Na+ channels, only leak

2. Membrane gradually becomes less negative• More Na+ coming in than K+ leaving

Pacemaker Potential (Autorhythmic Cells)Pacemaker Potential (Autorhythmic Cells)

3. One of 2 Ca2+ channels open (T) (prior to threshold)

• Short acting channel

4. Once threshold is reached, 2nd Ca2+ channels open (L) & membrane depolarized

5. Return is similar to nerve cell• Calcium begin to close• K+ leaves cell

Self-inducedaction potential

Slowdepolarization(pacemakerpotential)

Figure 9.10 Page 310Figure 9.10 Page 310

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Conduction System of the HeartConduction System of the HeartFigure 9.11Page 311

Sinoatrial(SA) node

Rightbranchof bundleof His

Purkinjefibers

Leftbranchof bundleof His

Atrioventricular(AV) node

Internodalpathway

Interatrialpathway

Action Potential DischargeAction Potential Discharge

20 – 40Bundle of His &Purkinje fibers

40 – 60AV node

70 – 80SA node

AP’s per minuteTissue

Cardiac Contractile CellsCardiac Contractile Cells

1. Explosive increase in Na+ (similar to skeletal)

2. Membrane potential remains positive (despite decrease in Na+ permeability)

• Plateau phase:Activation of slow L-type Ca2+ channelsDecrease in K+ permeability

3. Falling phase due to inactivation of Ca2+

channels & increase in K+ permeability

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Action potentialin cardiaccontractile cell

Travels downT tubules

Entry of small amount of Ca2+

from ECF

Release of large amount of Ca2+

from sarcoplasmicreticulum

CytosolicCa2+

Troponin-tropomyosin complex in thin filaments pulled aside

Cross-bridge cycling between thick and thin filaments

Thin filaments slide inward between thick filaments

Contraction

Figure 9.16Page 316

Figure 9.16Page 316

Induces larger influx of Ca2+

Thresholdpotential

AP of Contractile Cardiac CellsAP of Contractile Cardiac Cells

Plateauphase ofaction potential

Path of ConductionPath of Conduction

Autorhythmic to Contractile

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Figure 9.14Page 314

Figure 9.14Page 314

Interatrial pathway

Right atrium Left atrium

Right ventricle Left ventricle

SA node

AV node

Purkinjefibers

Bundleof His

Internodalpathway

Electrocardiogram (ECG) (EKG)Electrocardiogram (ECG) (EKG)

Records the electrical activity of the heart• Size• Position• Rate• Condition (healthy/sick)

ElectrocardiogramElectrocardiogram

••PP--wavewave–Atrialdepolarization

••QRS complexQRS complex–Ventricular depolarization

••TT--wavewave–Ventricular repolarization

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Relationship Between the

ECG and Cardiac

Contraction

Relationship Between the

ECG and Cardiac

Contraction

Actionpotential

Contractileresponse

Refractoryperiod

Figure 9.17Page 317

Figure 9.17Page 317

Diagnostic Use of the ECGDiagnostic Use of the ECGECG abnormalities may indicate coronary heart disease• ST-segment depression can indicate myocardial ischemia