MCCN SDAP X - Med-Surg Exam 1 (EKG) Questions and Answers, A+

SA node - cORRECT sOLUTION Fires in the atrium at 60-100 bpm AV node - cORRECT sOLUTION Fires in the ventricles at 40-60 bpm Purkinje Fibers - cORRECT sOLUTION Fire in the ventricular walls at 20-40 bpm Conduction system of the heart - cORRECT sOLUTION SA node -- Internodal pathways -- AV node -- Bundle of His -- Left and Right Bundle Branches -- Purkinje Fibers Myocardial cells - cORRECT sOLUTION Produce mechanical function (contractility), measured by BP and HR Pacemaker cells - cORRECT sOLUTION Generate and conduct electrical impulses, measured by EKG monitor. Polarization - cORRECT sOLUTION Resting state, inside of the cell is negatively charged Depolarization - cORRECT sOLUTION An electrical event (influx of Na) that causes muscle contraction Repolarization - cORRECT sOLUTION Return to resting state from contraction (outward diffusion of K) P wave - cORRECT sOLUTION Atrial depolarization/contraction. Impulse originates in SA node, Na influx. PR interval - cORRECT sOLUTION Beginning of the P wave to the beginning of the QRS complex, usually 0.12-0.20 seconds, greater than 0.20 seconds indicates 1st degree heart block. Q wave - cORRECT sOLUTION Pathologic if it is at least 0.04 seconds wide or more than 25% the total amplitude of the QRS complex; pathologic Q wave is indicative of infarction (cell necrosis). QRS Complex - cORRECT sOLUTION Ventricular depolarization/contraction. Impulse originates in AV node, Na influx. 0.04-0.10 seconds. (Greater than 0.10 seconds is ventricular rate?) ST segment - cORRECT sOLUTION Lasts about 0.08 seconds, more than 1mm/small-square depressed (ischemia) or elevated (active injury, STEMI) is significant and indicates damage to cardiac muscle. Normal ST is isoelectric