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Chapter 13,14,15 - Chapters 13,14 and 15 Cardiovascular...

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1 Chapters 13,14, and 15 Cardiovascular Function Transportation Gases Nutrients Wastes Regulation Hormones Temperature Protection Clotting Immune System Chapters 13 - Cardiac Function Heart Structure • 4 Chambers (atria + ventricles) Right side = Pulmonary Left side = Systemic • A-V valves (Tricuspid + Mitral) Aortic + Pulmonary valves Cardiac Function continued The primary purpose of the heart is to exert pressure against the blood, in order to initiate flow. Heart Function = Blood Flow Heart Exerts Pressure Against Blood Heart Contracts Heart Conducts Action Potentials
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2 Pacemaker Cells Autorhythmicity - automatic nature of heartbeat. Pacemaker Cells Each is capable of both a) generating action potentials and b) responding to them 1) Sinoatrial (SA) Node - 70 impulses/min 2) Atrioventricular (AV) Node – 50 impulses/min 3) Purkinjie Fibers – 30 impulses/min The SA Node determines the cardiac rate (pacemaker) in a healthy heart ..... Why??? Electrical Connections of the Heart • Long refractory periods allow the myocardial cells avoid being stimulated to contract again until after they relax.
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3 • The electrical impulse begins in the SA node SA node and spreads through both atria by electrical conduction from one myocardial cell to another. • The impulse then excites the AV Node AV Node and continues through the bundle of His bundle of His which divides into right and left bundle branches. Purkinje fibers Purkinje fibers transmit the impulse into the ventricular muscle. Conduction System of the Heart Spread of Excitation Through the Heart Heart must contract in an exact sequence in order to be effective. The sequence of contraction is controlled by the specific path of electrical excitations through the heart. Therefore, the spread of electrical activity is vital for proper cardiovascular function. The spread of excitation may be detected by electrodes + recorded by an electrocardiogram (ECG).
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