Lesson 32 - Circulation II

32: circulation II Monday, April 15, 2024 1:04 PM which of the following statements about the evolution of circulatory systems is true? a. an open circulatory system is restricted to less mobile animals b. a closed circulatory system separates oxygenated and deoxygenated blood c. an ectotherm requires blood circulation, even if the circuits are not completely separate d. an endotherm requires a high rate of blood flow to collect high levels of metabolic waste how the heart beats • rhythm from regular contraction (systole) and relaxation (diastole): a 0.8 second cycle in humans • valves keep blood flowing in the right direction • beats originates in the heart ○ autorhythmic cells (pacemaker) sets rate and timing for cardiac muscle contraction • pacemaker cells are found in all chordates • arthropods, molluscs, annelids, and other invertebrates also have comparable cells a patient comes in for a routine check-up. as you listen to their heart through the stethoscope, you hear a small swooshing sound along with the regular "lubb-dupp" of a cardiac cycle. what does this swooshing, or murmuring, sound likely indicate? a. high blood pressure pushing blood through the heart too quickly b. a blockage within the vena cava c. a damaged heart valve leading to blackflow from a ventricle to an atrium d. damage to the cardiac muscles arteries and veins • all blood vessels have a central lumen (cavity) lined with endothelium (layer of epithelial cells) • arteries: endothelium surrounded by thick walls arteries and veins • all blood vessels have a central lumen (cavity) lined with endothelium (layer of epithelial cells) • arteries: endothelium surrounded by thick walls ○ smooth muscle (flexible) that dilates or constricts to control blood flow ○ connective tissue (strong) supports the high pressure of blood flow from the heart • veins: walls about 1/3 thickness of arteries ○ same tissues composition as arteries ○ blood flowing black to heart at much lower pressure ○ valves maintain unidirectional blood flow capillaries • slightly wider than a red blood cell • thin walls: just endothelium and basal lamina ○ exchange between blood and interstitial fluid • flow varies depending on organ/structure • flow regulated by arterioles, sphincters the first stage of heart disease is atherosclerosis, the hardening of arteries through the accumulation of fatty deposits. atherosclerosis often starts with an injury to the endothelium. which factor or factors increase the risk of atherosclerosis? I) low blood pressure, II) high blood pressure, III) a diet high in cholesterol, IV) smoking a. I & III b. II & III c. I, III, & IV d. II, III, & IV blood pressure • ventricular contraction generates pressure • systolic pressure: ○ highest pressure ○ ventricles contract • diastolic pressure: ○ lower pressure, arteries bounce back • mean pressure decreases as blood moves away from the heart ○ narrowing of blood vessels increases resistance blood flow • diastolic pressure: ○ lower pressure, arteries bounce back • mean pressure decreases as blood moves away from the heart ○ narrowing of blood vessels increases resistance blood flow • blood flow velocity drops when blood enters arterioles, capillaries ○ large vessels branch into many smaller vessels ○ increase in total cross-sectional area decreases velocity exchange of materials • O2 and CO2, small solutes diffuse through pores in capillary walls • blood cells and proteins too large to diffuse • blood pressure pushes fluid out ○ osmotic gradient between blood and interstitial fluid pulls fluid in • lymphatic system returns fluid ○ net loss of fluid from blood into interstitial space ○ fluid returns to veins entering heart blood • plasma (55%) ○ liquid matrix where nutrients, wastes, gases, and hormones travel ○ dissolved ions § buffer blood and maintain osmotic balance § affect muscle and nerve activity ○ plasma proteins § buffer blood § defense (antibodies) § clotting factors • red blood cells (~ 44%) ○ erythrocytes ○ most numerous blood cells ○ biconcave shape increases surface area ○ hemoglobin: iron-containing protein transports O2 ○ lack nuclei and mitochondria (more hemoglobin) ○ each cell transports 1 billion molecules of O2 • white blood cells (< 1%) ○ leukocytes ○ 5 major types ○ fight infections ○ lack nuclei and mitochondria (more hemoglobin) ○ each cell transports 1 billion molecules of O2 • white blood cells (< 1%) ○ leukocytes ○ 5 major types ○ fight infections § phagocytic removal of microbes § mount immune responses against unfamiliar substances ○ increase in numbers when you are ill • platelets (< 1%) ○ fragments of specialized bone marrow cells ○ clotting § positive feedback § breaks in blood vessels attract platelets § platelets release clotting factor, triggers enzyme to convert coagulant from inactive to active form § coagulant aggregates into threads that form clot structure production of blood cells • from multipotent stem cells located in bone marrow • blood cells replaced regularly ○ O2 delivery low, kidneys secrete a hormone that stimulates RBC production circulation and gas exchange