I9 - Heart Physiology I. Cardiac Muscle (compare to...

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Heart Physiology I. Cardiac Muscle (compare to Skeletal Muscle) Cardiac Muscle Cells fairly short semi-spindle shape branched, interconnected connected (intercalated discs) electrical link (gap junction) common contraction (syncytium) 1 or 2 central nuclei dense "endomysium" high vasculature MANY mitochondria ( 25 % space) almost all AEROBIC (oxygen) myofibers fuse at ends T tubules wider, fewer Skeletal Muscle Cells very long cylindrical shape side-by-side no tight binding no gap junctions independent contract multinucleated light "endomysium" medium vasculature less mitochondria (2%) myofibers not fused T tubules at A/I spot II. Mechanism of Contraction of Contractile Cardiac Muscle Fibers 1. Na + influx from extracellular space, causes positive feedback opening of voltage- gated Na + channels; membrane potential quickly depolarizes (-90 to +30 mV); Na + channels close within 3 ms of opening.
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I9 - Heart Physiology I. Cardiac Muscle (compare to...

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