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 •4Chambers (atria + ventricles) • Right side = Pulmonary Left side = Systemic •A-Vvalves (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 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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Cardiac Cycle 1. Atrial Systole 2a. Atrial Diastole (Atrial Filling) 2b. Ventricular Systole 3. Ventricular Diastole (Ventricular Filling) Cardiac Cycle continued • The ventricles are about 80% filled before the atria contract. • When the ventricles contract the pressure increase closes AV valves and opens aortic and pulmonary artery valves. • Blood is ejected from the ventricles until the pressure within them falls below the pressure in the arteries, causing arterial valves to close • Ventricular contraction ejects about 2/3 of their blood. • When the pressure in the ventricles falls
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This note was uploaded on 08/05/2011 for the course APK 2105 taught by Professor Brooks during the Summer '07 term at University of Florida.

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

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