<prompt> Choose the TRUEFALSE statements regarding cardicac conduction functions: a The SA node is composed of a cluster of small fusiform cells in the sulcus terminalis at the right atrial-superior vena caval junction b The SA nodal aery arises from the right coronary aery in 20 and the left circumflex aery in 80 of persons c SA node dysfunction may be completely asymptomatic d Almost all patients with SA node dysfunction develop supraventricular tachycardia, usually atrial fibrillation or atrial flutter e Failure to increase the hea rate with exercise is referred to as chronotropic incompetencea,b,c,d,e-True None-Falsea,e-True b,c,d-Falsea,c,e-True b,d-Falseb,c,d-True a,e-False  <response>: The SA nodal aery arises from the right coronary aery in 55-60 and the left circumflex aery in 40-45 of persons. One-third to one-half of patients with SA node dysfunction develop supraventricular tachycardia, usually atrial fibrillation or atrial flutter. Ref: Harrisons Principles of Internal Medicine, 18th Edition, Page 1869 