Blood pressure can be buffered by___. ()
A. venous return
B. heart rate
C. cardiac contractility
D. elasticity of aorta
E. rate of transfusion
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The preload of the ventricle can be expressed as ()
A. end-diastolic volume of the ventricle
B. end-systolic volume of the ventricle
C. aortic pressure
D. the ventricular volume in the rapid ejection period
E. the ventricular volume in the isovolumetric relaxation period
Phase 3 of the action potential in the cardiac working cells is formed by ___. ()
A. deactivation of Na+ channel
B. Na+ influx
C. K+ efflux
D. Ca2+ influx
E. Cl- influx
QRS complex signifies ___. ()
A. depolarization of the atria
B. depolarization of the ventricles
C. systole of ventricles
D. systole of atria
E. diastole of ventricles
Which of the following normally serves as the pacemaker of the heart? ()
A. SA node
B. the atria
C. A-V node
D. the Purkinje fiber
E. the ventricle
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