Chapter 44 Gas Exchange and Circulation[1]

Chapter 44 Gas Exchange and Circulation[1] - Chapter 44,...

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Unformatted text preview: Chapter 44, Part 2 CIRCULATION Chapter 44, Part 2 CIRCULATION Transport Summary Circulation *Complex multicellular organisms need an efficient circulatory system to deliver nutrients and oxygen to all cells. *2 types of circulatory systems * Open: *Closed: *3 Functions of Vertebrate Circulatory Systems * Transportation * Respiratory: * Nutritive: * Excretory: * Regulation * Protection Blood *55% Plasma (liquid), 45% cells *Plasma solutes *Nutrients, wastes (N2 and CO2), hormones *Ions – primarily Na, Cl, K and HCO3 *Proteins – albumin, globulins, fibrinogen *Blood cells * Erythrocytes (RBC) – most numerous, circulating RBCs have no nucleus or other organelles. 1 ■ Contain hemoglobin with iron atoms that bind and carry O2 Contain Produced in red bone marrow from “stem cells” * Erythropoietin – hormone produced by kidney that stimulates RBC production. Process of RBC production = erythropoiesis. * Leukocytes (WBC) ­ ~1% of blood cells, 6 types involved in different types of immune responses. Can migrate out of blood vessels into tissues. * Platelets – fragments of megakaryocytes in bone marrow. Form first plug when a blood vessel is cut and induce fibrin formation (from fibrinogen). Blood Vessels *Arteries carry blood away from the heart, veins carry blood toward the heart. Capillaries connect arterial and venous systems. *Wall structure ***Capillaries * Arteries branch from aorta into smaller and smaller vessels. * Arterioles and precapillary sphincters regulate blood flow into capillaries. * Capillaries *Smallest blood vessels, extensive branching allows blood delivery to every cell. *Wall is one cell thick allowing gases, water and dissolved substances to flow into and out of interstitial space around the cells. *Veins and venules *Exposed to lower blood pressures, walls are much thinner. *Blood flow depends on venous pump (skeletal muscle contraction), valves and negative pressure in chest. Lymphatic System * Open circulatory system of blind­ended capillaries, lymphatic vessels, nodes, and organs (spleen and thymus). *Blood capillaries lose water at the arterial end and reclaim most of it at the venous end. That not reclaimed is picked up by lymph capillaries and returned 2 to venous system near the heart. to venous system near the heart. *Nodes and organs filter lymph and remove and destroy debris, cancer cells and bacteria. They also activate some immune cells. The Heart ­ Anatomy *Cardiac Cycle ­ terms *Ventricular contraction = systole *Ventricular relaxation = diastole. *Sequence of Cardiac Cycle: *Atria fill with blood which flows into ventricles. *Atria contract and empty contents into ventricle, AV valves close. *Ventricles contract and increased pressure of blood opens semilunar valves; blood flows out of heart. Backflow closes semilunar valves and ventricle relaxes. *Valves *Atrioventricular (AV valves) The Heart * Semilunar valves Double­loop Circulatory System * Pulmonary circulation: *Deoxygenated blood from right ventricle through pulmonary arteries to lungs. *Oxygenated blood flows back to left atrium through pulmonary veins. * Systemic circulation: *Oxygenated blood to left ventricle and out through aorta to systemic arteries and capillaries. *Deoxygenated blood collected in veins that empty into superior and inferior vena cavae that empty into right atrium and then to right ventricle. Blood Flow and Blood Pressure * Blood pressure (BP) is a function of the CO and the resistance to flow (R). Blood pressure increases as CO or resistance increases in the arteries. 3 * Vasoconstriction – smooth muscle contracts reducing diameter of blood vessels. * Vasodilation – smooth muscle relaxes increasing diameter of blood vessels. – Blood pressure (BP) is a function of the CO and the resistance to flow (R). Blood pressure increases as CO or resistance increases in the arteries. – Vasoconstriction – smooth muscle contracts reducing diameter of blood vessels. – Vasodilation – smooth muscle relaxes increasing diameter of blood vessels. Regulation –Blood pressure is monitored by baroreceptors (pressure sensors) in the aorta and carotid arteries. –When BP increases, the baroreceptors send impulses via nerves to the cardiovascular control center in the brain (medulla oblongata). –This center, in turn, sends impulses to the heart and arteries causing a decrease in HR &/or SV and vasodilation which decreases BP. 4 Arterial Blood Pressure Arterial Blood Pressure *Measured using a pressure cuff with gauge, a sphygmomanometer. Sounds = blood turbulance. *Cuff is inflated to 150 mmHg + cutting off blood flow to arm. *Cuff pressure gradually released until sound is heard = systolic pressure. *Cuff pressure continues to be released until no sound is heard = diastolic pressure. Activation of the Heart *Contraction of the heart is initiated by an electrical event = depolarization. Recording of the depolarization is the ECG. *Sequence * Sinoatrial (SA) node – right atrium cells spontaneously depolarize = pacemaker. Depolarization spreads over atria = P wave of ECG. Atria subsequently contract. *Depolarization spreads to atrioventricular (AV) node, through Bundle of His, on to Purkinji fibers and then the ventricular muscle = QRS wave on ECG. Ventricles subsequently contract. *Ventricular muscle repolarizes = T wave on ECG and ventricles subsequently relax. Cardiovascular Disease ****#2 killer (still #1 in women) *Atherosclerosis – cholesterol plaques in arteries restrict flow, *coronary arteries. *Stroke *Arteriosclerosis – “hardening” of vessel walls; normal with aging. *Hypertension 5 ...
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