QUESTION 4
A 35-year-old female who has been having heavy menstrual periods for 6 months presents to her obstetrician with complaints of increased fatigue during her normal work-outs at the gym. As part of her evaluation, her physician performs a complete blood cell count. The hemoglobin is 10.9 g/dl (normal range: 12-16), hematocrit is 34% (normal range: 37-47%), MCV is 70 fL/cell (normal is 76-96), platelet count is 256,000/mm3 (normal range: 150-400,000), and white cell count is 5100/mm3 (normal range: 4500-11,000). Of the following, what is the mechanism for her symptoms?
A. Hypoxia
B. Ischemia
C. Thrombosis
D. Immunologic reaction
E. Sepsis
Answer for Question 4
Answer: A (hypoxia)
Explanation: given her heavy menstrual bleeding, she has developed iron deficiency anemia. Being anemic, she has decreased oxygen carrying capacity in her blood, and with exercise, is unable to meet the oxygen requirements of her active tissue, and is thus hypoxic. Her blood flow would be normal; thus, she is not ischemic. And, given the scenario presented, there is no indication of thrombosis, an immunologic reaction, or sepsis.
QUESTION 5
A 51-year-old male presents to the emergency room with his wife with complaints of chest pain that has been occurring for the past 4 hours. He describes the chest pain as being behind his sternum and feeling as though someone is compressing his chest. The pain does not vary with inspiration or expiration. Laboratory testing reveals an elevated troponin I, indicating damage to cardiac myocytes. A cardiac catheterization procedure is performed, revealing an obstruction of the proximal distribution of the left anterior descending coronary artery. Which of the following mechanisms best describes how the injury to the myocytes occurred?
A. Hypoxia
B. Ischemia
C. Trauma
D. Immunologic
E. Infectious
Answer for Question 5
Answer: B (ischemia).
Explanation: the patient is having an acute myocardial infarct. The left anterior descending coronary artery has a thrombus that is obstructing blood flow to the myocardium, causing ischemia. While hypoxia is a component of ischemia, as, when blood cannot flow to the tissue, oxygen cannot be delivered; however, the better answer is ischemia, which is reduced blood flow. While trauma, immunologic processes, and infectious agents can affect the heart and potentially cause a myocardial infarct, given the obstruction to the blood flow described and that the obstruction is most commonly due to atherosclerosis, C, D, and E are not the best answer.
QUESTION 6
A 50-year-old male develops a sudden squeezing sensation in his chest while walking up stairs at work. He tells a co-worker, who calls an ambulance. Fifteen minutes later, he is being evaluated in the emergency room, and with intravenous nitroglycerin, his chest pain has resolved. Cardiac enzyme testing reveals normal concentrations. A cardiac catheterization is performed. The procedure identifies significant coronary artery atherosclerosis, but no thrombus. If ultrastructural analysis of the myocytes had been performed, they would have revealed cellular swelling. Of the following, which cellular component was most responsible for the ultrastructural changes?
A. Na/Ca counter-transporter
B. Na/K pump
C. Na/H counter-transport
D. Na/glucose co-transporter
E. CyclinD
Answer for Question 6
Answer: B (Na/K pump).
Explanation: The lack of blood flow to the cardiac myocytes (i.e., ischemia) would restrict production of ATP by the mitochondria. Without ATP, the Na/K pump would not be able to effectively maintain the normal sodium gradient across the plasma membrane; sodium would enter the cell, followed by water, leading to swelling of the cell. The primary role of the Na/K pump is to maintain this gradient, and it is the primary system responsible for maintaining the gradient. The Na/Ca counter-transporter would transport sodium into the cell (and calcium out). The Na/H counter-transporter and Na/glucose co-transporter would transport sodium into the cell and are more commonly found on renal and intestinal cells and not cardiac myocytes. Cyclin D plays a regulatory role in the cell cycle and is not responsible for maintaining the sodium gradient, and thus, would not contribute significantly to cellular swelling.