HESC2501 Lecture Notes - Lecture 6: Cardiac Muscle, Myocyte, Skeletal Muscle
14 Dec 2019
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Importance = required as there is no antagonist muscle contracting to help elongate the heart muscle: cardiac muscle as a syncytium i. Slow channels have the unique characteristics of both opening more slowly and closing later after depolarization than do the fast channels. The opening of both of these channels allows a large quantity of sodium and calcium to flow into the muscle fiber: potassium channels in cardiac muscle have decreased permeability (5x less permeable) when the membrane is depolarized. This effect seems to be due to the presence of excess calcium (from the slow channels) within the muscle fiber. This contraction forces blood back into the direction of the ventricles snapping shut the aortic and pulmonary valves. Indices of contractility = 1) increased contractility effects on the pressure-volume curve = ejection curve shifts up and to the left. It shifts up because the ventricle is pushing with greater force.
