Conduction System
Atrinodal
AN; aka transitional zone; upper junction region of AV node [p37]
His-Purkinje system
Bundle of His, bundle branches, and Purkinje fibers [p38]
Right bundle branch
Innervates he right ventricle [p38]
Nodal
N; midportion region of AV node [p37]
Nodal-His
NH; lower junctional region where the fibers of AV node merge gradually with the bundle of His [p37]
Septal fascicles
Relays the impulse to the midseptum [p38]
Posterior fascicles
Relays the impulse to the posterior portions of the left ventricle [p38]
Normal pacemaker sites
SA node (primary pacemaker) 60-100bpm AV junction 40-60 bpm Purkinje fibers 20-40 bpm [p39]
Left bundle branch
Sends electrical impulses to the interventricular septum and left ventricle [p38]
Fascicles
Small bundles of nerve fibers; the left bundle branch breaks into 3 divisions- anterior fascicles, posterior fascicles, and septal fascicles [p38]
Purkinje fibers
Spread from the interventricular septum into the papillary muscles; they continue downward to the apex of the heart [p38]
Anterior fascicles
Spreads the electrical impulse to the anterior portions of the left ventricle [p38]
AV junction
The AV node and the non-branching portion of the bundle if His; consists of conduction tissue that provides electrical links between atria and ventricles [p37]
Bundle of His
The lower portion of the AV junction; aka common bundle; aka atrioventricular bundle; located in the upper portion of the interventricular septum; conducts impulses to right and left branches; receives double blood supply[p38]
Wenckebach's bundle
The middle internodal pathway [p37]
Thorel's pathway
The posterior internodal pathway [p37]
accessory pathway
abnormal conduction tract between the atria and ventricles [p37]
AV node
an area of specialized tissue between the atria and the ventricles of the heart, which conducts the normal electrical impulse from the atria to the ventricles.[p37]
built-in (intrinsic) rate
heart's pacemaker has intrinsic rate that becomes slower and slower from the SA node down to the end of the His-Purkinje system; 60-100 bpm [p36]
SA node
sinoatrial node; normal heartbeat is the result of an electrical impulse that begins in SA node; 10-20 mm long, 2-3 mm wide (adult) [p36]; located in the upper posterior part of the right atrium where the superior vena cava and the right atrium meet; less than 1mm from the epicardial surface and richly supplied by sympathetic and parasympathetic nerve fibers [p37]
conduction system
specialized electrical (pacemaker) cells in the heart are arranged in a system of pathways [p35]
Bachmann's bundle
the anterior internodal pathway; conducts impulses to the left atrium [p37]
when would other areas of the heart assume pacemaker responsibilities?
~SA node fails to fire (generate impulse) ~SA node fires too slowly ~SA node fails to activate the surrounding atrial myocardium [p36]
