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Cardiovascular System Blood Vessels Arteries • Carry blood away from the heart • Lumen • Wall – Tunica interna – Tunica media – Tunica externa • Pulse Arterioles • Tiny arteries • Primary resistance vessel Capillaries • Thin wall, one cell layer • Diffusion Venules • Tiny veins Veins • • • • • • Carry blood towards the heart Low pressures Valves Skeletal muscle Breathing Sinuses Blood reservoirs • Veins and sinuses Blood velocity • Inversely proportional to total cross sectional area of vessel • Slowest in capillaries Blood flow • Flow = Pressure/Resistance Pressure • Force that drives blood through the vessels due to pumping of heart • Highest in aorta • Lowest in vena cava • Pulse Resistance • Blood viscosity • Blood vessel length • Vessel radius – Resistance = 1/radius4 – Arterioles Relationships • F = P/R • CO = P/R • CO = Mean aortic pressure/total peripheral resistance • CO = Mean arterial pressure/total peripheral resistance • Mean arterial pressure = CO x TPR Arterial Pressure • Neural controls – Vasomotor fibers • Sympathetic efferent • Vasodilator • Vasoconstrictor Arterial Pressure • Neural controls – – – – Vasomotor Center Cardiac Center Baroreceptors in aortic arch and carotid sinus Chemoreceptors in aortic and carotid bodies for oxygen, carbon dioxide, hydrogen Baroreceptors Chemoreceptors Arterial Pressure • Chemicals & Hormones – – – – Angiotensin Epinephrine ADH (Vasopressin) Blood volume Epinephrine Arterial Pressure • • • • Measurement 120/80 mmHg Systolic pressure Diastolic pressure Venous Return • • • • • Low pressures Related to peripheral venous pressure Skeletal muscles Valves Breathing (thoracoabdominal pump) Arterial Pressure and Gravity • Gravity – Pressure increases inferiorly – Increased capillary filtration to decrease blood volume – Baroreceptors – Movement of skeletal muscle Exercise and CV system • Skeletal muscle vasodilation – CNS sympathetic vasodilator fibers – Low O2 levels – Increased local vasodilator chemicals Exercise • • • • • Visceral vasoconstriction Increased sympathetic stimulation to heart Increased venous return HR, SV, CO increase Mean arterial pressure increases Pulmonary Circuit Systemic Circuit • Aorta to Vena Cava Fetal Circulation • Placenta • Umbilical cord • Lung and liver bypass Hypertension • • • • • Causes: Adrenal tumor Kidney Disease Volume loading 90% unknown Consequences • • • • • • Heart – enlarged Angina Aneurysm Sclerosis Rupture of vessel Kidney disease Treatment • • • • • Lose weight, exercise Decrease salt, diuretics Stop smoking, alcohol, caffeine Biofeedback Vasodilator drugs, e.g. isoproteronol
