Phosphorylation of two serines in Ser-X-Ser motif at the extreme C-terminus of the MH2 domain by the activated RI separates the two domains, exposing the NLS for binding to importins

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#Id: 5256

#Unit 7. System Physiology – Animal

Contractile cells constitute the majority of atrial & ventricular tissues.

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#Id: 5257

#Unit 7. System Physiology – Animal

Conducting cells constitute tissues of the SA node, the atrial internodal tracts, the AV node, the bundle of His, & the Purkinje system.

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#Id: 5258

#Unit 7. System Physiology – Animal

Conducting cells are specialized muscle cells which function to rapidly spread action potentials over the entire myocardium.

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#Id: 5259

#Unit 7. System Physiology – Animal

The action potential spreads throughout the myocardium in the following sequence:

SA node  Atrial internodal tracts and atria  AV node  Bundle of His  Purkinje system  Ventricles

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#Id: 5260

#Unit 7. System Physiology – Animal

Myocardial fibers have a resting membrane potential of approximately –90 mV.

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#Id: 5261

#Unit 7. System Physiology – Animal

The individual fibers are separated by membranes, but depolarization spreads radially (syncytium) because of the presence of gap junctions.