Chapter 21 Assessment of Cardiovascular Function · Overview of Anatomy and Physiology o Three layers: endocardium, myocardium, epicardium o Heart encased in a thin, fibrous sac called pericardium o Four chambers: Right atrium and ventricle, left atrium and ventricle o Atrioventricular valves: tricuspid and mitral o Semilunar valves: aortic and pulmonic · Coronary arteries o Cardiac conduction system (electrophysiology) · Anatomy of the Heart Aortic arch Superior vena cava Right pulmonary artery Left pulmonary artery Interatrial septum Descending aorta Pulmonary veins Pulmonary veins Left atrium Pulmonic valve Aortic valve Mitral valve Left ventricle Chordae tendinae Papillary muscle Right atrium Tricuspid valve Inferior vena cava Right ventricle Papillary muscle Interventricular Visceral pericardium Parietal pericardium septum Endocardium Myocardium Unoxygenated blood Oxygenated blood Epicardium Pericardial space o o *PMI @ midclavicular line 5th ICS . Pericardial Sac · Coronary Arteries Aortic valve Right pulmonary veins Superior vena cava Aortic arch Left pulmonary veins Coronary sinus Superior vena cava Left atrium Right atrium Circumflex branch of left coronary artery Right atrium Anterior descending branch of left coronary artery Inferior vena cava Right coronary artery Right ventricle Right ventricle Left circumflex branch Posterior descending branch of right coronary artery Left ventricle o A B · Cardiac Conduction System: Electrophysiology
SA node Left atrium AV node Right atrium Left Bundle of His Right bundle branch Right ventricle ventricle Left bundle branch Purkinje fibers o • Cardiac Action Potential: Why the heart acts good, bad, or ugly o Depolarization: electrical activation of cell caused by influx of sodium into cell while potassium exits cell o Repolarization: return of cell to resting state caused by reentry of potassium into cell while sodium exits o Refractory periods " Effective refractory period: phase in which cells are incapable of depolarizing " Relative refractory period: phase in which cells require stronger-than-normal stimulus to depolarize · Cardiac Action Potential Cycle PHASE 1 Rapid repolarization - PHASE 2 Plateau +40 - +20 - 0 - -20 - PHASE 0 Potential (mV) -40 - Rapid PHASE 3 depolarization -60 - Final repolarization -80 - PHASE 4 Resting -100 o Na+ Ca++ K+ Na+ K+ Cell membrane o Figure ff5-4 • Cardiac Cycle o Refers to the events that occur in the heart from the beginning of one heartbeat to the next o Number of cycles depends on heart rate o Each cycle has three major sequential events: " Diastole · Atrial systole · Atrial kick 15-ff5% of ventricular blood volume · Ventricular systole · Frank-Starling Law o Within normal physiology, the more myocardial muscle fibers stretch, the greater the tension in those fibers and the greater the force of the contraction of the ventricle. · Frank-Starling as a balloon
o Ventricle =balloon o Preload = amount the balloon can stretch End diastolic volume= amount of water in the balloon after filling o Afterload=someone's hands holding the balloon o Contractility= how stretchy the balloon fibers are o Stroke volume=amount of water sprayed out from balloon if released · Stroke Volume o Comprised of 3 factors: