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CPR: Chapter 9 (8/15/2011) I. Physiology of ca rdiac muscle A. 3 types o f cardiac muscle: atrial, ventricular, and specialized excitatory an d conductive fibers 1. Atrial and ventricular fibers contract in the same manner as skeletal muscle, but the duration of contraction is longer 2. Excitatory and conductive fibers con tract very little, bu t instead act to either: a. Automa tically discharge a. Conduct action po tentials g enerated by automat ically disc harging fibers through the heart muscle B. Physiologic anatomy of cardiac muscle 1. Appear striated 2. Myofibrils c ontain act in and myo sin that act in the same manner as in skeletal muscle 3. Diffe rences with skele tal musc le a. The p resenc e of the pro tei n Tit in i. Defi niti on = a prot ein th at allo ws pas sive el asti c elon gatio n of the sa rcomeres after contraction i. Impo rtan ce = requ ired as t here is n o anta goni st musc le con trac ting to h elp elongate the heart muscle a. Car dia c mus cle a s a sy ncy tium i. Inter cala ted dis cs = gap j unct ions th at lie be twee n the ca rdia c muscl e fiber s connected in series (such that cardiac muscle fibers are much shorter than skeletal muscle fibers) and parallel 1. Function = allow an actio n potentia l transmitted thro ugh one muscle f iber to be transmitted to an adjacent muscle fiber 2. Atri al vs. ventricular sync ytia 1. Sepa rated f rom each o ther by fi brou s tissu e that sur roun ds the AV openings 2. Action po tentials p ass between the atria and ventric les only through specialized conduction tissue called the AV bundle a. Impo rtance = allows the atria to c ontr act a short time ahead of the ventricles C. Acti on po tent ials in cardiac muscle 1. Basics
