Heart Anatomy and Function PDF

 Electrical Activity of Heart Cardiac Muscle Cells The Intrinsic Conduction System Pacemaker Potentials Cardiac Muscle Action Potentials Heart characteristics Atomicity: the ability to spontaneously depolarize itself and then trigger action potentials and spread all ove...

 Electrical Activity of Heart Cardiac Muscle Cells The Intrinsic Conduction System Pacemaker Potentials Cardiac Muscle Action Potentials Heart characteristics Atomicity: the ability to spontaneously depolarize itself and then trigger action potentials and spread all over the muscle layer of the heart to trigger more heart muscle to contract  Cardiac Muscle Cells Cardiac muscle is striated (contains actin and myosin) and branching Adjacent cells connected by intercalated discs, which contain: Desmosomes: mechanically hold cells together as heart contracts Gap Junctions: electrically connect cells  Plasma membranes of Desmosome adjacent cardiac muscle fibers Gap junction Action potential Intercalated disc (b) Intercalated discs contain two types of membrane junctions: mechanically important desmosomes and electrically important gap junctions. Fig. 9-6b, p. 310  Functional Syncytium Heart muscle contraction is ALL-OR-NONE (no graded contractions ex: skeletal muscle recruitment)  Cardiac cells Noncontractile cells: AV Node SA Node SA Node AV Node Bundle of His (AV Bundle) right and left bundle branches Purkinje Fibers Contractile cells: Purkinje fibers Bundle of His SA Node The SA Node is located in the upper right atrium AV Node Fastest, sets the pace of the heart SA Node 70 – 80 action potentials per minute at rest Activity spreads to BOTH atria and to the AV Node Purkinje fibers Bundle of His AV Node The AV Node is located in the lower right atria, near the AV Node ventricular septum SA Node 2nd fastest, only sets the pace if there is damage to the SA Node 40-60 action potentials per minute Activity pauses first, then spreads to Bundle of His AV Nodal Delay = 100 ms, due to fibrous tissue, slow conduction Purkinje fibers Bundle of His Bundle of His & Purkinje Fibers The Bundle of His is located within the interventricular AV Node septum, and has a right and a left SA Node branch The Purkinje Fibers travel up the outer walls of the ventricles Slowest, not life sustaining 20-40 action potentials per minute activity spreads to ventricles Purkinje fibers Bundle of His Protect pdf from copying with Online-PDF-No-Copy.com