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Unformatted text preview: the SA node pass across the right atrium to the A-V node. Areas in the ventricles are not yet
93. A. Interpreting each peak in Figure 1 indicates that the height of R extends above +1.0 mV,
while S extends to about -0.5mV. Thus, the net change is closest to 1.5mV.
94. C. The P wave is initiated by depolarization at the S-A node, whereas depolarization of the
ventricles is associated with the QRS complex. The distance between these points represent
the time needed for the impulse to reach the Bundle of His and Purkinji fibers in the
ventricular walls (the T wave represents a later point in time when the ventricles repolarize).
95. B. Knowledge about the sequence of cardiac cycle should immediately help eliminate
answers A and D. Repolarization of the atria coincides with ventricular depolarization.
Answer C is highly improbable. It is unlikely that an instrument designed to pick up the
electrical changes in an organ as vital at the heart, would not be sensitive enough to detect
each event in the sequence.
96. D. Since the QRS complex represents depolarization of the ventricles, a prolonged
depolarization would make this part of the EKG wider. A higher QRS complex would
indicate a stronger depolarization (contraction) not a longer one.
97. C. It should be understood that regulation of heart rate is under autonomic control. The
sympathetic division is responsible during stressful situations (“fight or flight” response),
whereas the parasympathetic division controls the heart during normal activity.
98. B. Each of the electrolytes is vital to membrane function and muscle contraction except
Chloride, which does not play a role in these processes.
99. B. This molecule of CO2 would pass through the left ventricle and travel out to the tissues,
return to the heart via the superior vena cava, enter the heart through the right atrium, and Page 11 of 12 finally, exit the heart through the pulmonary vein on its way to lungs in order to leave the
100. D. Activated helper T cell interacts with B cell displaying same antigen complex, B cell
then becomes activated, B cell divides and gives rise to clone, which differentiate, forming
plasma cells, and finally antibodies are produced. Page 12 of 12...
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- Spring '11