cardiac physiology (iii) a. rüçhan akar ankara university school of medicine december- 2003 a....
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Cardiac Physiology(III)
Cardiac Physiology(III)
A. Rüçhan Akar
Ankara University
School of Medicine
December- 2003
A. Rüçhan Akar
Ankara University
School of Medicine
December- 2003
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Coronary CirculationCoronary Circulation
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Coronary Blood Flow Coronary Blood Flow
• coronary blood flow: 250 ml/min
• 5% of resting cardiac output
• 60-80 ml blood/100g tissue/min
• entirely during diastole~ aortic diastolic pressure minus LVDP~ duration of diastole
• pressure < 150 mmHg
• oxygenated by superb membrane oxygenator-”the lungs”
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Cerebral Blood FlowCerebral Blood Flow
• Cerebral blood flow: 750 ml/min
• 15% of resting cardiac output
• 50-55 ml blood/100g tissue/min
• Cerebral blood flow: 750 ml/min
• 15% of resting cardiac output
• 50-55 ml blood/100g tissue/min
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Right coronary blood flow
Left coronary blood flow
* The peak left coronary flow occurs at the end of isovolumetric relaxation
*
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Cessation of Myocardial Blood Flow Cessation of Myocardial Blood Flow
mitochondria
cellular pO2 < 5mmHg within seconds
oxidative phosporilation stops
cytosol
anaerobic glycolysis
glycogen
glucose-6-phosphate
pyruvate
lactate
cellular acidosis
depletion of ATP
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Depletion of ATP < 50% of Normal Level-Depletion of ATP < 50% of Normal Level-
irreversible lethal cell injury
• glycolysis is blocked
• increasing cellular acidity
• protein denaturation
• structural, enzymatic, nuclear changes
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Blood VesselBlood Vessel
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Measurement of Cardiac OutputMeasurement of Cardiac Output
Fick PrincipleFick Principle
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The Fick Principle
Q = VO2
CaO2 – CvO2
.
–
Q: cardiac outputVO2: O2 consumption
CaO2:arterial O2 content
CvO2: mixed venous O2 content
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Blood VesselBlood Vessel
• Intima primarily the endothelial lining
• Mediavascular smooth muscle, collagen, elastin
• Adventitiaconnective tissue
• Intima primarily the endothelial lining
• Mediavascular smooth muscle, collagen, elastin
• Adventitiaconnective tissue
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Vascular EndotheliumVascular Endothelium
Vasodilators VasoconstrictorsVasodilators Vasoconstrictors
Nitric OxideProstacyclinEndothelium-derived hyperpolarizing factorBradykinin
Endothelin-1 Angiotensin II
Wilson SH, Lerman A.Heart Physiology and Pathophysiology, Academic Press(edited by Sperelakis N.) 473-480
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L-Arginine is converted to NO by the enzyme nitric oxide synthase (NOS)
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Nitric Oxide (NO)Function
Nitric Oxide (NO)Function
• Vasodilator
• Inhibitor of vascular smooth muscle cell proliferation
• Inhibitor of platelet adherence/aggregation
• Inhibitor of leukocyte/endothelial interactions
• Vasodilator
• Inhibitor of vascular smooth muscle cell proliferation
• Inhibitor of platelet adherence/aggregation
• Inhibitor of leukocyte/endothelial interactions
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Endothelin-1(ET-1)
Endothelin-1(ET-1)
• Peptide first sequenced in 1988
• Most potent vasoconstrictor in humans
• Maintenance of basal arterial vasomotor tone
• Strong chemoattractant for circulating monocytes and macrophage activation “proatherogenic”
• Peptide first sequenced in 1988
• Most potent vasoconstrictor in humans
• Maintenance of basal arterial vasomotor tone
• Strong chemoattractant for circulating monocytes and macrophage activation “proatherogenic”
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Endothelial DysfunctionEndothelial Dysfunction
• Imbalance of endothelium-derived relaxing and contracting factors• Imbalance of endothelium-derived
relaxing and contracting factors
Atherosclerotic risk factors
Decreased NO bioavailabilityIncreased levels of ET-1
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Functional Classification of Vessel WallFunctional Classification of Vessel Wall
• elastic arteries• muscular arteries• resistance vessels• capillaries (exchange vessels) • venules (capacitance vessels)
• elastic arteries• muscular arteries• resistance vessels• capillaries (exchange vessels) • venules (capacitance vessels)
JR Levick, 1995An Introduction to Cardiovascular PhysiologyButterworth-Heinemann
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Elastic ArteriesElastic Arteries
• aorta, pulmonary artery and major branches
• diameter = 1-2 cm
• tunica media is rich in elastin (extensible)
• collagen (prevents overdistension)
• aorta, pulmonary artery and major branches
• diameter = 1-2 cm
• tunica media is rich in elastin (extensible)
• collagen (prevents overdistension)
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intima
media
Elastic fibers
Smooth muscle
adventitia
AORTA
Bergman RA, Afifi AK, Heidger PMAtlas of Microscopic Anatomy, 1989W.B. Saunders Company
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Conduit (Muscular) ArteriesConduit (Muscular) Arteries
• diameter = 1mm-1cm
• popliteal, radial, cerebral, coronary arteries
• tunica media is thicker, contains more smooth muscle
• rich autonomic nerve supply (contraction and relaxation)
• diameter = 1mm-1cm
• popliteal, radial, cerebral, coronary arteries
• tunica media is thicker, contains more smooth muscle
• rich autonomic nerve supply (contraction and relaxation)
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Resistance VesselsResistance Vessels
• main resistance to blood flow resides in the;
– smallest, terminal arteries (diameter = 100-500m)
– arterioles (< 100m) “single layer of muscle in the media”
• richly innervated by vasoconstrictor nerve fibres
• actively regulate local blood flow to match local demand
• main resistance to blood flow resides in the;
– smallest, terminal arteries (diameter = 100-500m)
– arterioles (< 100m) “single layer of muscle in the media”
• richly innervated by vasoconstrictor nerve fibres
• actively regulate local blood flow to match local demand
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Capillaries (Exchange vessels)Capillaries (Exchange vessels)
• diameter: 4-7m
• wall: single layer of endothelial cells
• wall thickness = 0.5m
• large cross-sectional area
• slow blood velocity
• red cell transit time = 1-2 sec
• diameter: 4-7m
• wall: single layer of endothelial cells
• wall thickness = 0.5m
• large cross-sectional area
• slow blood velocity
• red cell transit time = 1-2 sec
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Arteriovenous AnastomosisArteriovenous Anastomosis
• shunt vessels ( diameter = 20-135m)
• connect arterioles to venules, bypassing the capillaries
• skin, nasal mucosa
• temperature regulation
• shunt vessels ( diameter = 20-135m)
• connect arterioles to venules, bypassing the capillaries
• skin, nasal mucosa
• temperature regulation
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The Veins“Capacitance Vessels”
The Veins“Capacitance Vessels”
• diameter 50-200m
• thin wall
• in limb veins, intima possesses pairs of valves
• low resistance to flow
• storing large volumes of blood under low pressure
• ~ 60-70% of the circulating blood volume
• diameter 50-200m
• thin wall
• in limb veins, intima possesses pairs of valves
• low resistance to flow
• storing large volumes of blood under low pressure
• ~ 60-70% of the circulating blood volume
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Distribution of blood volume in a resting man ( 5.5 litres)
Folkow B, Neil E. 1971, Oxford University Press, London