Cardiac muscle cells in the atria are capable of contracting spontaneously because of a spontaneous depolarization resulting from:
A. an inward current through a hyperpolarization activated channel
B. cyclic changes in the activity of the Na+,K+-ATPase
C. slow leak of Ca++ through the dihydropyridine receptor
D. cyclic changes in the activity of the sarcolemmal Ca++ pump
E. cyclic changes in the activity of SERCA
ANS: A
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Fill in the blank(s) with correct word
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