BSCI 202 Lecture Notes - Lecture 9: Heart Valve, Atrioventricular Node, Cardiac Muscle
2 Mar 2017
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Bsci202: the heart ii: electrical impulses and contraction. In a sheep heart, might point just straight down: cut right along axis to see inside. Cardiac muscle cells that contract and squeeze on ventricle. Intercalated discs, where cells join: desmosomes: anchor two cells together; under mechanical stress, less likely to separate, gap junctions: core channel allows ion to move from one cell to another; electrically connected. All cardiomyocytes contract as a unit, or none do. 99% contractile, 1% auto rhythmic: auto rhythmic: can set rhythm by themselves, do not need external stimulus. Auto rhyth(cid:373)ic cells se(cid:374)d (cid:373)essage to left atriu(cid:373) as (cid:449)ell (cid:448)ia bach(cid:373)a(cid:374)"s bu(cid:374)dle: tract. Once sent to slow av node, there is a . 1 s pause: atria should contract and drain first. 20% blood: tracts are narrow, so it takes longer to spread message. Ecg or ekg: all action potentials at a given time, three waves: P wave: depolarization of sa node atria.
