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EMU AHPR 200 - Chapter 6-Circulatory & Cardiovascular System

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Chapter 6-The HeartLocation of the Heart- Cardiopulmonary Resuscitation-CPR- Thoracic Cavity-Between the lungs in the mediastinum- Heart is shaped like a blunt cone- Points down and to the lef- Rests at an angle with the majority of it’s mass to the lef of the sternumAbbreviations- CVT-Cardiovascular technologist- ECG-Electrocardiogram- ED-Emergency Department- EKG-Electocardiogram- DOB-Difficulty of Breathing- STAT-Immediately Functions of the Heart1. Pump Blood-As your heart contracts, it generates pressure that moves your blood through your blood vessels.2. Route Blood-Your heart essentially has two pumps: one on the right side that sends blood through the pulmonary circulation of your lungs and back to the second pump on your left side, which sends blood through the systemic circulation of your body. Your heart valves make this one-way flow of blood possible. 3. Regulate Blood Supply-The changing metabolic needs of your tissues and organs-for example, when you exercise-are met by changes in the rate and force of your heart’s contractions.Structure of the HeartThe heart wall consists of 3 layers1. Endocardium: Connective tissue lining the inside of your heart.2. Myocardium: Cardiac muscle cells that contract to enable your heart to pump blood.3. Epicardium: An outer single layer of cells overlying a thin layer of connective tissue.a. The pericardium is a double-layered connective tissue sac that surrounds and protects your heart.Blood Supply to Heart Muscle- Because your heart beats continually and forcefully, it requires an abundant supply of oxygen and nutrients. To meet this need, your cardiac muscle has it’s own blood circulation called the coronary circulation. This system of arteries arises directly from the aorta.- If any of your coronary arteries become blocked, the blood supply to a part of your cardiac muscle is cut off (ischemia) and the cells supplied by that artery die (necrosis) within minutes. This is a myocardial infarction (MI) or a “heart attack”.Blood Flow through the Heart- Your heart has four chambers through which your blood flows. These chambers are the:o Right Atriumo Right Ventricleo Lef Atriumo Lef Ventricle- Your right and left atria are separated by a thin muscle wall called the interatrial septum. Your right and left ventricles are divided by a thicker muscle wall called the interventricular septum.- Your left ventricle pumps blook to all the parts of your body (except the lungs) through the systemic circulation. Oxygen (O2) and nutrients are delivered to your body’s cells, and carbon dioxide (CO2) and metabolic waste products are removed from the cells. Thisdeoxygenated blood, via the veins returns to the heart where the right ventricle pumps blood into the pulmonary circulation to the lungs. In the lungs, the carbon dioxide wastematerial is exchanged for oxygen from inhaled air. This oxygenated blook then travels through the pulmonary veins back to the left side of the heart.- You have four valves that work together to ensure the correct flow of blood through your heart; on the right side are the tricuspid and pulmonary valves, and on the left sideare the mitral (bicuspid) and aortic valves.Abbreviations:- AV-Atrioventricular- BP-Blood Pressure- P-Pulse- R-Respiration- SA-Sinoatrial- T-Temperature- VS-Vital SignsThe Heartbeat- The actions of the four heart chambers are coordinated. When the atria contract (atrial systole), the ventricles relax (ventricular diastole). When the atria relax (atrial distole), the ventricles contract (ventricular systole). Then the atria and ventricles all relax briefly. This series of events is a complete cardiac cycle, or heartbeat. - The “lub-dub, lub-dub” sounds heard through the stethoscope are made by the heart valves snapping as they close. If there is an abnormality in valve closure, it will produce an extra, abnormal sound called a murmur.Electrical Properties of the Heart. - As your heart muscles contract, they generate a small electrical current that sustains your heartbeat rhythm through a conduction system. o A small region of specialized muscle cells in the right atrium’s sinoatrial (SA) node initiates your heartbeat. The SA node is the pacemaker of your heart’s rhythm. o Electrical signals from the SA node spread out through the atria and rejoin at the atrioventricular (AV) node. The AV is the electrical gateway to the ventricles. o Electrical signals leave the AV node and travel to the ventricular myocardium where they stimulate the ventricular myocardium to contract, creating your heartbeat.- Sinus Rhythm is the term used to describe a normal heartbeat, where normal electrical conduction leads to a ventricular rate of about 60 to 80 beats per minute. An abnormal cardiac rhythm is called and arrhythmia or a dysrhythmia.- An electrocardiograph is a device that picks up the heart muscle’s electrical changes andamplifies them to record an electrocardiogram in the form of waves.Disorders of the Heart - Arrhythmias are abnormal or irregular heartbeats, and six types are commonly seen:o Premature Beats-occur most ofter in elderly people and are usually associated with caffeine and stress.o Atrial Fibrillation (A-fib)-occurs when the two atria quiver rather than contract correctly to pump blood. This causes blood to pool in the atria and sometimes clot.o Ventricular Tachycardia (V-tach)-is a rapid heartbeat occurring in the ventricles.o Ventricular Arrhythmias include: Premature ventricular contractions (PVCs), which result when extra impulses arise from a ventricle; and Ventricular Fibrillation (V-fib), which occurs when the ventricles lose control, quivering instead of pumping.o Heart Block occurs when interference in cardiac electrical conduction prevents the atria’s contractions from coordinating with the ventricles’ contractions.o Palpitations are brief but unpleasant sensations of a rapid or irregular heartbeat.They can be brought on by exercise, anxiety, and stimulants like caffeine.- Arrhythmias can be treated with medications, but some patients require mechanical pacemakers. Pacemakers consist of a battery, electronic circuits, and computer memory to generate electronic signals. These signals are carried along thin, insulated wires to theheart muscle. Pacemakers are ideal for patients with a very slow heart rate (bradycardia).- In emergency situations, external defibrillation is performed through automatic external defibrillators, or AEDs. AEDs send an electric shock


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