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GREENFIELD COMMUNITY COLLEGEPRACTICAL NURSING CERTIFICATE PROGRAMNUR 107: Alterations in Cardiovascular FunctioningSpring 2020Student Learning Outcomes:1. Explain normal cardiac anatomy and physiology including the coronary circulation, conduction system, and hemodynamics.Heart Structure•Covered by the pericardium•There are three layers of tissue making up the heart:•Epicardium•Myocardium•EndocardiumThe Pericardium•Fibrous sac that encases the heart•A space between the epicardium & pericardial sac filled with pericardial fluid•Decreases friction during heart contractionHeart Chambers•Atria: the two upper chambers whose main purpose is to collect blood. They are thin-walled and separated by the interatrial septum
•Ventricles: the two lower chambers whose main purpose is to pump blood. They have thicker walls and are larger than the atria. They are separated by the interventricular septumHeart Valves•Delicate structures made primarily of endocardium that maintain the direction of blood flow through the heart•Tricuspid •Pulmonary•Mitral/Atrioventricular•AorticBlood Flow Through the HeartCardiac Conduction•A pathway of electrical impulses that generates a heartbeat•Impulses are reflected in an EKG•Heart beat is regulated by•Automaticity•Nervous system
•HormonesConduction pathway: A pathway of electrical impulses that generates a heartbeat. a. Normally starts at the SA node; a specialized node of tissue located in the right atrium that generates an electrical impulse 60-80 times per minute. Because this is the normally the most rapid rate in the heart; the SA node is called the heart’s pacemaker. b. The impulse leaves the Sa node via the intra-atrial pathways to the AV node, located just at the junction of all four chambers. The AV node can also initiate electrical impulses, but at a much slower rate of about 50-60 beats per minute-it can take over from the SA node if necessary. The impulse is delayed for a split second here while the atria contract and blood enters the ventriclesc. The impulse continues through the ventricles via the Bundle of HIS; the right and left bundle branches and the purkinje fibers. d. This pathway is reflected in the EKG and is an electrical process based on the cardiac muscle’s unique ability to initiate and electrical impulse and to conduct that impulse from one muscle cell to the other.Determinants of Blood Flow:Resistance & ViscosityVascular resistance is controlled by the nervous system & hormones that regulate the diameter of the vessels.When the vessel diameter enlarges, resistance falls and blood flow increases. When vessel diameter decreases, resistance rises and blood flow decreases.Viscosity of blood is affected by the hydration status of the body. When dehydration occurs, blood viscosity increases; thicker blood causes an increase in blood pressure.