1. Which of the following statements is NOT correct?
A. The walls of the ventricles are thicker because the ventricles pump blood under higher pressure over greater distances.
B. The walls of the atria are thicker because the atria receive blood under pressure.
C. The wall of the right ventricle is thinner than that of the left ventricle because the right side of the heart pumps blood a shorter distance at lower pressure.
D. Although the right side of the heart has a smaller workload, the right and the left ventricle simultaneously eject the same amount of blood.
E. All of these choices are correct
2.The semilunar valves open when pressure in the right and left ventricles exceeds that in the pulmonary trunk an aorta, respectively.
3. Contractility can be decreased by
a,increased end-diastolic volume
b, presence of positive inotropic substances
c. decreasing inflow of calcium ions
d. increased end-diastolic volume and presence of positive inotropic substance.
e. increased end-diastolic volume, presence of positive inotropic substance, and decreasing inflow of calcium ions.
4. When compared to auto rhythmic fibers, contractile cardiac myocytes.
a. have leaky sodium channels to cause spontaneous depolarization
b. have a peak action potential of about +10 mV.
c. re polarize to about -60mV
d. have a resting membrane potential of about -90mV
e. depolarize when voltage-gated slow calcium channels close