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For the re-polarization phase of an SA nodal cell action potential,
A. Calcium and potassium channels close
B. sodium and chloride channels open
C. Calcium channels close and potassium channels open
D. Calcium channels open and sodium channels close
E. Sodium and potassium channels open - Answers C
According to the Frank Starling law,
A. the greater the resistance from the arteries , the higher the blood pressure
B. as the volume of blood entering the heart increases, ventricular contractions become more foreceful
C. the faster the heart rate, the larger the stroke volume
D. the more calcium available to the heart cell, the more forcefully it will contract - Answers B
Once an SA nodal cell reaches threshold, the depolarization phase occurs during which
a. calcium comes in through fast voltage gated channels
b. sodium moves out through slow voltage gated channels
c. calcium moves through slow voltage gated channels
d. potassium moves out through fast voltage gated channels
e. potassium comes in through fast voltage gated channels - Answers A
in an ECG, what does the T wave represent
a. repolarization of the ventricles
b. closure of the av valves
c. depolarization of the left ventricle
d. depolarization of the atria
e. depolarization of the right ventricle - Answers a
atrial contraction occurs just before
, a. isovolumetric relaxation
b. isovolumetric contraction
c. atrial relaxation and ventricular filling
d. ventricular ejection - Answers b
which of the following would cause a decrease in cardiac output?
a. addition of positive inotropic agents
b. an increase in venous return
c. an increase in heart rate
d. an increase in afterload - Answers d
during the S-T segment, what is occurring within cardiac muscle cells
a. calcium is entering and potassium is leaving ventricular cells
b. sodium channels are beginning to open in ventricular cells and calcium is entering through slow
channels in atrial cells
c. sodium is rapidly diffusing out of atrial muscle cells
d. potassium is entering atrial cells and sodium is leaving ventricular cells - Answers a
as with action potentials in other types of cells, the repolarization of cardiac muscles cells involves the
a. binding of ACh to ACh receptor
b.simultaneous closure of sodium channels and opening of calcium channels
c. entrance of calcium through voltage-gated channels
d. entrance of sodium through voltage gated channels
e. exit of potassium through voltage gated channels - Answers e
cardiac output is usually expressed in
a. mL per minute
b. mL per beat
c. mm Hg
d. beats per minute - Answers a