GSU BIOL 2240 - Cardiovascular-4 (37 pages)

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Cardiovascular-4



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Cardiovascular-4

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Pages:
37
School:
Georgia State University
Course:
Biol 2240 - Intro to Human Physiology
Intro to Human Physiology Documents
Unformatted text preview:

Cardiovascular system consists of Muscular pump the heart Series of conduits blood vessels Fluid blood Heart Function Generates blood pressure to move blood through vessels Regulates blood supply changes in rates and force to meet demands Routes blood through systemic or pulmonary circulation pulmonary vein Pulmonary circuit The human heart has four chambers two atria and two ventricles The atria receive blood from the body and deliver it to the ventricles The ventricles then pump the blood out to the body The right ventricle pumps blood through the pulmonary circuit The left ventricle pumps blood through the systemic circuit Rt atrium Rt ventricle Systemic circuit Valves prevent backflow of blood Atrioventricular AV valves lie between the atria and ventricles and prevent backflow when ventricles contract The pulmonary valve and aortic valve SL valves lie between the ventricles and the major arteries and prevent backflow when ventricles relax Tricuspid valve Bicuspid valve The right atrium receives deoxygenated blood from the body through large veins pulmonary vein Pulmonary circuit Rt atrium Rt ventricle Superior vena cava blood from upper body Inferior vena cava blood from lower body Systemic circuit Blood passes from the right atrium through Rt AV tricuspid valve into the right ventricle The atrium contracts then the ventricle the AV valve closes and blood is pumped through the pulmonary artery to the lungs where it is oxygenated pulmonary vein Pulmonary circuit Rt atrium Rt ventricle Systemic circuit Oxygenated blood returns to the left atrium of the heart through the pulmonary veins The ventricle fills as blood enters through Left AV bicuspid valve The left atrium contracts then the ventricle the aortic valve opens and blood circulates through the aorta pulmonary vein Pulmonary circuit Rt atrium Rt ventricle Systemic circuit 1 Direction of blood flow Blood returning to heart fills atria putting pressure against AV valves AV valves are forced open Atrium Cusp of atrioventricular valve open 2 As ventricles fill AV valve flaps hang limply into ventricles Chordae tendineae 3 Atria contract forcing additional blood into ventricles Ventricle Papillary muscle a AV valves open atrial pressure greater than ventricular pressure Atrium 1 Ventricles contract forcing blood against atrioventricular valve cusps 2 Atrioventricular valves close Lub 3 Papillary muscles contract and chordae tendineae tighten preventing valve flaps from everting into atria b AV valves closed atrial pressure less than ventricular pressure Cusps of atrioventricular valve closed Blood in ventricle Aorta Pulmonary trunk As ventricles contract and Intraventricular pressure rises blood is pushed up against semilunar valves forcing them open a Semilunar valves open As ventricles relax and intraventricular pressure falls blood flows back from arteries filling the cusps of semilunar valves and forcing them to close Dupp b Semilunar valves closed Cardiac cycle first the two atria contract then the two ventricles contract Two phases Diastole when ventricles relax Systole when ventricles contract Creates pressure gradient that causes blood to flow p p Blood pressure changes are measured with a sphygmomanometer and a stethoscope Systolic value pressure at which blood begins to flow after being compressed pulsing sound Diastolic value pressure at which blood flows freely pulsing sound stops Pressure at which blood starts to flow is the systolic P Pressure at which blood flows freely is diastolic P Ests of how hard the heart has to work to get blood flowing Conduction system Cardiac muscles cells are in close contact with each other through desmosomes and gap junctions spread of action potentials result in coordinated contraction Cardiac muscles cells have the capacity to generate action potentials electrical signals independent of the nervous system Some cells are pacemaker cells and generates the electrical signals for the heartbeat An action potential is generated in the sinoatrial SA node pacemaker cells The action potential spreads in the atria through gap junctions and they contract together SA node AV node Bundle of His Purkinje fibers The action potential in the atria are picked up by the atrioventricular node and passes it down through the bundle of His after a short delay The bundle divides into right and left bundle branches that run to the tips of the ventricles Purkinje Fibers carry impulses to heart apex and up the walls of both ventricles A contraction spreads through ventricles upward from apex Ventricles contract in a wringing motion SA node AV node Bundle of His Purkinje fibers Blood is a connective tissue cells in a liquid extracellular matrix called plasma Most of the cells in blood are erythrocytes or red blood cells that transport gases The hematocrit is the percentage of blood made up of RBC Formed elements Plasma 55 of whole blood Buffy coat Leukocytes platelets 1 Withdraw 2 Centrifuge blood sample blood and place in tube separation based on density Erythrocytes RBC 45 of whole blood Blood Plasma 90 water Proteins mostly produced by the liver E g albumin globulin fibrinogen Respiratory gasses hormones nitrogenous byproducts nutrients and electrolytes Plasma Formed elements 55 of whole blood Buffy coat Erythrocytes Formed elements WBCs only complete cells in blood RBCs have no nuclei or organelles Platelets cell fragments Most formed elements survive in blood for few days Most blood cells originate in bone marrow RBC Plasma Formed elements 55 of whole blood Buffy coat Erythrocytes Platelets WBC Erythropoiesis formation of red blood cells Erythropoietin a hormone released in the kidney in response to hypoxia stimulates erythropoiesis Red blood cells are produced in bones red marrow They lose their organelles eg nucleus and are released into blood Immature RBCs mature in blood turn white to red as they accumulate Hb Circulate 120 days and then rupture Red marrow also produces megakaryocytes that break off into cell fragments called platelets megakaryocytes Platelets initiate blood clotting when activated by collagen exposed in damaged blood vessels They release chemical clotting factors which activate other platelets feedback mechanism Steps in blood clotting Platelet activation Conversion of prothrombin thrombin active form inactive form to Conversion of fibrinogen to fibrin active Fibrin threads form mesh that clots blood and seals vessel Blood Vessels Delivery system that begins and ends at the heart


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