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Cardiac Physiology III

Coronary Circulation. Coronary Blood Flow. coronary blood flow: 250 ml/min5% of resting cardiac output60-80 ml blood/100g tissue/minentirely during diastole~ aortic diastolic pressure minus LVDP~ duration of diastolepressure < 150 mmHgoxygenated by superb membrane oxygenator-"the lungs". Cer

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Cardiac Physiology III

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    1. Cardiac Physiology (III) A. Rüēhan Akar Ankara University School of Medicine December- 2003

    2. Coronary Circulation

    3. 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”

    4. Cerebral Blood Flow Cerebral blood flow: 750 ml/min 15% of resting cardiac output 50-55 ml blood/100g tissue/min

    6. 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

    7. Depletion of ATP < 50% of Normal Level- irreversible lethal cell injury glycolysis is blocked increasing cellular acidity protein denaturation structural, enzymatic, nuclear changes

    8. Blood Vessel

    9. Measurement of Cardiac Output Fick Principle

    11. Blood Vessel Intima primarily the endothelial lining Media vascular smooth muscle, collagen, elastin Adventitia connective tissue

    12. Vascular Endothelium Vasodilators Vasoconstrictors

    14. Nitric Oxide (NO) Function Vasodilator Inhibitor of vascular smooth muscle cell proliferation Inhibitor of platelet adherence/aggregation Inhibitor of leukocyte/endothelial interactions

    15. 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”

    16. Endothelial Dysfunction Imbalance of endothelium-derived relaxing and contracting factors

    17. Functional Classification of Vessel Wall elastic arteries muscular arteries resistance vessels capillaries (exchange vessels) venules (capacitance vessels)

    18. Elastic Arteries aorta, pulmonary artery and major branches diameter = 1-2 cm tunica media is rich in elastin (extensible) collagen (prevents overdistension)

    20. Conduit (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)

    21. Resistance Vessels main resistance to blood flow resides in the; smallest, terminal arteries (diameter = 100-500mm) arterioles (< 100mm) “single layer of muscle in the media” richly innervated by vasoconstrictor nerve fibres actively regulate local blood flow to match local demand

    22. Capillaries (Exchange vessels) diameter: 4-7mm wall: single layer of endothelial cells wall thickness = 0.5mm large cross-sectional area slow blood velocity red cell transit time = 1-2 sec

    23. Arteriovenous Anastomosis shunt vessels ( diameter = 20-135mm) connect arterioles to venules, bypassing the capillaries skin, nasal mucosa temperature regulation

    24. The Veins “Capacitance Vessels” diameter 50-200mm 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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