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Action potential of cardiac contractile cells

Action potential of cardiac contractile cells. Varies considerably in ionic mechanisms and shape from SA node potential unlike auto rhythmic cells cardiac muscle has a stable resting potential of -90 mV until excited by PMP. Action potential of cardiac contractile cells.

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Action potential of cardiac contractile cells

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  1. Action potential of cardiac contractile cells • Varies considerably in ionic mechanisms and shape from SA node potential • unlike auto rhythmic cells cardiac muscle has a stable resting potential of -90 mV until excited by PMP

  2. Action potential of cardiac contractile cells • Voltage dependant permeability changes responsible for plateau • Activation of slow calcium channels (ca channels of SR slow to close ) (SR is slow to remove ca from the cytosol) • Decreased K permeability (prevents rapid repolarization of membrane) • Development of muscle tension (myocardial contraction) following closely behind the depolarization and plateau

  3. Excitation contraction coupling in CCC • AP in CCC • Travels down T Tubules • Entry of small amount of Ca from ECF • Release of large amount of Ca from SR • Increased I cytosolic Ca • TTC in thin filaments pulled aside • Cross bridge cycling between thick and thin filaments • Thin filaments slide inward between thick filaments …..contraction

  4. Refractory period • Like other excitable tissue , C muscle has refractory period • Cardiac muscle can not be restimulated until contraction is almost over • Making summation of contraction and tetanus • Chief factor responsible is inactivation of NA channels

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