Solutions to 100 passage-based Biology questions

Interpreting each peak in figure 1 indicates that the

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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 involved. 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 body. 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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