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Unformatted text preview: recruited all at once? a. Short refractory period b. Long refractory period c. Nothing, the all of the fibers of the heart contract at the same time d. The anatomical structure of the heart Answers: B 5. Which valve prevents the backwards flow of blood from the ventricles to the atrium? a. Aortic valve b. Ventricular valve c. Atrioventricular valve d. Semilunar valves e. Left atrium Answer: C...
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- Spring '10