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This 8 page Class Notes was uploaded by Jess Graff on Saturday February 20, 2016. The Class Notes belongs to BMS 508 at University of New Hampshire taught by Mary Katherine Lockwood, PhD in Spring 2016. Since its upload, it has received 15 views. For similar materials see Human Anatomy and Physiology II in Biological Sciences at University of New Hampshire.
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Date Created: 02/20/16
BMS 508.03 2/12/2016 Chapter 19 (cont) The Cardiovascular System (cont) Hemostasis • Hemostasis • The cessation of bleeding • Consists of 3 phases 1. Vascular phase 2. Platelet phase 3. Coagulation phase • The Vascular Phase • A cut triggers vascular spasm that lasts 30 minutes • 3 Steps of the Vascular Phase 1. Endothelial cells contract and expose basement membrane to bloodstream • Three Steps of the Vascular Phase • Endothelial cells 1. Release chemical factors ADP, tissue factor, and prostacyclin 2. Release local hormones, endothelins 3. Stimulate smooth muscle contraction and cell division • Endothelial plasma membranes become “sticky” 1. Seal off blood flow • The Platelet Phase • Begins within 15 seconds after injury • Platelet adhesion (attachment) 1. To sticky endothelial surfaces 2. To basement membranes 3. To exposed collagen fibers • Platelet aggregation (stick together) 1. Forms platelet plug that closes small breaks • Platelet Phase • Activated platelets release clotting compounds 1. Adenosine diphosphate (ADP) 2. Thromboxane A and 2erotonin 3. Clotting factors 4. Platelet-derived growth factor (PDGF) 5. Calcium ions • Factors That Limit the Growth of the Platelet Plug • Prostacyclin, released by endothelial cells, inhibits platelet aggregation • Inhibitory compounds released by other WBCs • Circulating enzymes break down ADP • Negative (inhibitory) feedback from serotonin • Development of blood clot isolates area • The Coagulation Phase • Begins 30 seconds or more after the injury • Blood clotting (coagulation) 1. Cascade reactions • Chain reactions of enzymes and proenzymes • Form three pathways • Convert circulating fibrinogen into insoluble fibrin • Clotting Factors • Also called procoagulants • Proteins or ions in plasma • Required for normal clotting • Three Coagulation Pathways • Extrinsic pathway • Intrinsic pathway • Common pathway • The Extrinsic Pathway • Begins in the vessel wall • Outside bloodstream • Damaged cells release tissue factor (TF) • TF + other compounds = enzyme complex • Activates Factor X • The Intrinsic Pathway • Begins with circulating proenzymes • Within bloodstream • Activation of enzymes by collagen • Platelets release factors (e.g., PF-3) • Series of reactions activates Factor X • The Common Pathway • Where intrinsic and extrinsic pathways converge • Forms complex prothrombin activator • Converts prothrombin to thrombin • Thrombin converts fibrinogen to fibrin • Feedback Control of Blood Clotting • Stimulates formation of tissue factor • Stimulates release of PF-3 1. Forms positive feedback loop (intrinsic and extrinsic) • Accelerates clotting • Anticoagulants (plasma proteins) 1. Antithrombin-III 2. Alpha-2-macroglobulin • Heparin • Aspirin • Protein C (activated by thrombomodulin) • Prostacyclin • Calcium Ions, Vitamin K, and Blood Clotting • Calcium ions (Ca ) and vitamin K are both essential to the clotting process • Clot Retraction • Pulls torn edges of vessel closer together 1. Reducing residual bleeding and stabilizing injury site • Reduces size of damaged area 1. Making it easier for fibroblasts, smooth muscle cells, and endothelial cells to complete repairs • Fibrinolysis • Slow process of dissolving clot 1. Thrombin and tissue plasminogen activator (t-PA) • Activate plasminogen • Plasminogen produces plasmin 1. Digests fibrin strands BMS 508.03 2/12/2016 Chapter 20 The Cardiovascular System (cont) An Intro to the Cardiovascular System • The Pulmonary Circuit • Carries blood to and from gas exchange surfaces of lungs • The Systemic Circuit • Carries blood to and from the body • Blood alternates between pulmonary circuit and systemic circuit • 3 Types of Blood Vessels • Arteries • Carry blood away from heart • Veins • Carry blood to heart • Capillaries • Networks between arteries and veins • Capillaries • Also called exchange vessels • Exchange materials between blood and tissues • Materials include dissolved gases, nutrients, waste products • 4 Chambers of the Heart • Right atrium • Collects blood from systemic circuit • Right ventricle • Pumps blood to pulmonary circuit • Left atrium • Collects blood from pulmonary circuit • Left ventricle • Pumps blood to systemic circuit Anatomy of the Heart • The Heart • Great veins and arteries at the base • Pointed tip is apex • Surrounded by pericardial sac • Sits between 2 pleural cavities in the mediastinum • The Pericardium • Double lining of the pericardial cavity • Visceral pericardium • Inner layer of pericardium • Parietal pericardium • Outer layer • Forms inner layer of pericardial sac • Pericardial cavity • Between parietal and visceral layers • Contains pericardial fluid • Pericardial sac • Fibrous tissue • Surrounds and stabilizes heart • Superficial Anatomy of the Heart • Atria • Thin-walled • Expandable outer auricle (atrial appendage) • Sulci • Coronary sulcus divides atria and ventricles • Anterior interventricular sulcus and posterior interventricular sulcus • Separate left and right ventricles • Contain blood vessels of cardiac muscle • The Heart Wall • Epicardium • Myocardium • Endocardium • Epicardium (Outer Layer) • Visceral pericardium • Covers the heart • Myocardium (Middle Layer) • Muscular wall of the heart • Concentric layers of cardiac muscle tissue • Atrial myocardium wraps around great vessels • 2 divisions of ventricular myocardium • Endocardium (Inner Layer) • Simple squamous epithelium • Cardiac Muscle Tissue • Intercalated discs • Interconnect cardiac muscle cells • Secured by desmosomes • Linked by gap junctions • Convey force of contraction • Propagate action potentials • Characteristics of Cardiac Muscle Cells • Small size • Single, central nucleus • Branching interconnections between cells • Intercalated discs • Internal Anatomy and Organization • Interatrial septum separates atria • Interventricular septum separates ventricles
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