To initiate a smooth muscle cell contraction, calcium enters the cell and binds to
A. troponin, which then activates myosin light-chain kinase.
B. calmodulin, which then binds to and activates myosin light-chain kinase.
C. a myosin head, which then activates calmodulin.
D. myosin light-chain kinase, which then hydrolyzes ATP.
E. a phosphatase, which then removes the tropomyosin blockade.
B
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The esophagus passes through a hole in the diaphragm called the
A) esophageal hiatus. B) cardia. C) pylorus. D) upper esophageal sphincter. E) lower esophageal sphincter.
The bundle of His and Purkinje system facilitate the rapid spread of the action potential throughout the ventricles
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What occurs when one sympathetic preganglionic neuron synapses on several postganglionic neurons?
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