During the cardiac cycle of a normal healthy young adult（）
A. During the initial stage of ventricular contraction the volume of the ventricle does not change
B. During ventricular diastole the pressure in the left ventricle is close to 80 mm Hg （10.6 kPa）
C. During ventricular systole, all the blood in the ventricles is ejected
D. At the end of ejection, the blood pressure reached the highest level
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Which of the following organs is able to tolerate the greatest restriction in blood flow（）
A. skin
B. brain
C. heart
D. skeletal muscles
If the respiratory rate is increased from 12/min to 24/min, and the tidal volume volume is decreased from 500 ml to 250 ml, then（）
A. alveolar ventilation will decrease
B. pulmonary ventilation will decrease
C. pulmonary ventilation will increase
D. alveolar ventilation will increse
E. alveolar ventilation does not change
What kinds of channels open during the phase 2 of the ventricular action potential（）
A. Ca2+ channel and K+ channel
B. Na+ channel and K+ channel
C. Na+ channel and Cl- channel
D. Na+ channel and Ca2+ channel
Internal respiration is（）
A. gas exchange between the cells and the blood in the capillary
B. gas exchange between alveoli and blood in the capillary surrounding the alveoli
C. gas exchange between mitochondria and intracellular fluid
D. gas change between the cells in the tissue
E. gas exchange between alveoli and skeletal muscle cells
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