TEST BANK FOR ECGS MADE EASY6TH EDITION BY BARBARA

TEST BANK FOR ECGS MADE EASY6TH EDITION BY BARBARA 1. In most patients, the sinoatrial (SA) and atrioventricular (AV) nodes are supplied by the coronary artery. a. right b. left main c. circumflex d. left anterior descending ANS: A The SA node receives its blood supply from the SA node artery that runs lengthwise through the center of the node. The SA node artery originates from the right coronary artery in about 60% of people. The AV node is supplied by the right coronary artery in 85% to 90% of the population. In the remainder, the circumflex artery provides the blood supply. OBJ: Describe the location, function, and, when appropriate, the intrinsic rate of the following structures: sinoatrial node, atrioventricular bundle, and Purkinje fibers. 2. The intrinsic rate of the atrioventricular (AV) bundle is beats/min. a. 20 to 40 b. 40 to 60 c. 60 to 80 d. 80 to 100 ANS: B The AV bundle has pacemaker cells capable of firing at a rate of 40 to 60 beats/min. OBJ: Describe the location, function, and, when appropriate, the intrinsic rate of the following structures: sinoatrial node, atrioventricular bundle, and Purkinje fibers. 3. How do you determine whether the atrial rhythm on an ECG tracing is regular or irregular? a. Compare QT intervals. b. Compare PR intervals. c. Compare R to R intervals. d. Compare P to P intervals. ANS: D To evaluate the regularity of the atrial rhythm on a rhythm strip, the interval between two consecutive P waves is measured. The distance between succeeding P-P intervals is measured and compared. If the atrial rhythm is regular, the P-P intervals will measure the same. OBJ: Describe a systematic approach to the analysis and interpretation of cardiac dysrhythmias. 4. is the ability of cardiac pacemaker cells to spontaneously initiate an electrical impulse without being stimulated from another source, such as a nerve. a. Excitability b. Conductivity c. Automaticity d. Contractility ANS: C The ability of cardiac pacemaker cells to create an electrical impulse without being stimulated from another source is called automaticity. Excitability is the heart muscles’ ability to respond to impulse or stimulus. Conductivity is the ability of the cardiac cells to receive and transmit an electrical impulse. Contractility is the contraction of the heart muscle which produces the heartbeat. OBJ: Describe the primary characteristics of cardiac cells. 5. In the heart’s conduction system, the receive(s) an electrical impulse from the bundle of His and relay(s) it to the Purkinje fibers in the ventricular myocardium. a. atrioventricular (AV) node b. atria c. sinoatrial (SA) node d. right and left bundle branches ANS: D The right and left bundle branches divide into smaller and smaller branches and then into a special network of fibers called the Purkinje fibers. These fibers spread from the interventricular septum into the papillary muscles. They continue downward to the apex of the heart, composing an elaborate web that penetrates about one third of the way into the ventricular muscle mass. The fibers then become continuous with the muscle cells of the right and left ventricles. OBJ: Describe the location, function, and, when appropriate, the intrinsic rate of the following structures: sinoatrial node, atrioventicular bundle and purkinje fibers.