be230cLecture8

Depicted factors control formation of the

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Unformatted text preview: of LacZ transgene demonstrates both mixed and unmixed working and conducGng myocytes. The finding of mixed clusters indicates that conducGng cells share a common origin with working myocytes. The relaGvely small numbers of conducGng cells in the clusters indicates that they proliferate much less than working myoyctes Lineage RelaGonship Between the Working and ConducGng Myocytes •  •  •  Common lineage for conducGng and working myocytes Greater proliferaGon of working myoycte progenitors Control by neuregulin (NG) and endothelin (ET) Christoffels V M , and Moorman A F Circ Arrhythm Electrophysiol 2009;2:195 ­207 Mikawa et al., Seminars in Cell & Developmental Biology; 18, Issue 1 2007 90  ­ 100 8 4/25/13 Development of the Purkinje fiber system (PVCS) Christoffels V M , and Moorman A F Circ Arrhythm Electrophysiol 2009;2:195-207 Copyright © American Heart Association Development of the AVC and AVN. Depicted factors control formation of the atrioventricular (AV) canal and atrial or ventricular working myocardium (chamber), respectively, or are involved in establishing boundaries. Christoffels V M , and Moorman A F Circ Arrhythm Electrophysiol 2009;2:195-207 Copyright © American Heart Association Model for Influence of Hemodynamic Forces on Purkinje Fiber FormaGon 9 4/25/13 Autonomic RegulaGon of Cardiac Output •  ParasympatheGc Nervous System –  decreases HR and SV –  dominant at rest •  SympatheGc Nervous System –  increases HR and SV –  dominant during exercise/stress Autonomic Nervous System SchemaGc ParasympatheGc Effects •  Vagal nerves release acetylcholine at SA and A ­V nodes •  sGmulates muscarinic receptors •  increased K+ channel opening •  decreased sinus node rhythm •  decreased A ­V node transmission •  ventricular escape”, a form of arrhythmia that creates an ectopic beat in the absence of failure to transmit SA or AV node signals 10 4/25/13 SympatheGc Effects •  SympatheGc nerves release norepinephrine throughout heart •  sGmulates adrenergic receptors •  increased Ca+ and N...
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