A 52-year-old male suffered a myocardial infarction secondary to atherosclerosis and ischemia. Once oxygen returned to the damaged heart, reperfusion injury occurred as a result of:
Oxygenation of the cells
Free radical formation
Increased metabolic state
Lactic acid build-up
The Correct Answer is B
Choice A Reason:
Oxygenation of the cells is a necessary process during reperfusion, but it is not the direct cause of reperfusion injury. The injury occurs due to the sudden influx of oxygen, which leads to the formation of reactive oxygen species (ROS) or free radicals. These free radicals cause oxidative stress and damage to the myocardial cells.
Choice B Reason:
Free radical formation is the primary mechanism behind reperfusion injury. When blood flow is restored to the ischemic myocardium, the sudden reintroduction of oxygen leads to the production of free radicals. These free radicals cause significant oxidative damage to the cell membranes, proteins, and DNA, exacerbating the injury to the heart tissue.
Choice C Reason:
An increased metabolic state can occur during reperfusion as the cells attempt to recover from ischemia. However, it is not the direct cause of reperfusion injury. The primary issue is the oxidative stress caused by free radicals, not the metabolic changes themselves.
Choice D Reason:
Lactic acid build-up is a consequence of anaerobic metabolism during the ischemic period, not a cause of reperfusion injury. During ischemia, cells switch to anaerobic metabolism, leading to lactic acid accumulation. However, once oxygen is reintroduced, the focus shifts to the oxidative damage caused by free radicals rather than lactic acid.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice A: Calcium
Calcium plays a crucial role in various physiological processes, including muscle contraction, blood clotting, and nerve transmission. While calcium is essential for maintaining overall health, it is not directly associated with changes in blood pH. Calcium levels are tightly regulated by hormones such as parathyroid hormone (PTH) and calcitonin, but these do not significantly influence blood pH.
Choice B: Sodium
Sodium is a major extracellular electrolyte that helps regulate fluid balance, nerve function, and muscle contraction. Although sodium is vital for maintaining osmotic balance and blood pressure, it does not directly affect blood pH. Sodium levels are primarily controlled by the kidneys and hormones like aldosterone, which do not have a direct impact on the acid-base balance of the blood.
Choice C: Magnesium
Magnesium is involved in over 300 biochemical reactions in the body, including protein synthesis, muscle and nerve function, and blood glucose control. While magnesium is important for overall health, it does not have a direct role in altering blood pH. Magnesium levels are regulated by the kidneys and are essential for maintaining normal muscle and nerve function, but they do not directly influence the acid-base balance.
Choice D: Potassium
Potassium is a key intracellular electrolyte that plays a significant role in maintaining the acid-base balance of the blood. Changes in potassium levels can affect the pH of the blood. For example, hyperkalemia (high potassium levels) can lead to acidosis, while hypokalemia (low potassium levels) can lead to alkalosis. Potassium helps regulate the hydrogen ion concentration in the blood, which directly impacts the pH. Therefore, potassium is the electrolyte most closely associated with changes in blood pH.
Correct Answer is C
Explanation
Choice A Reason:
The exhaustion stage is the final phase of the general adaptation syndrome (GAS). It occurs when the body has been exposed to stress for a prolonged period and can no longer maintain resistance. Symptoms of exhaustion include fatigue, burnout, depression, and decreased stress tolerance. Since the student is experiencing an immediate response to a sudden stressor, this stage does not apply.
Choice B Reason:
Adaptation is not a specific stage in the general adaptation syndrome. The correct stages are alarm, resistance, and exhaustion. Therefore, this choice is incorrect.
Choice C Reason:
This is the correct answer. The alarm stage is the initial phase of the general adaptation syndrome, also known as the “fight-or-flight” response. During this stage, the body reacts to a stressor by activating the sympathetic nervous system, which leads to increased heart rate, rapid breathing, and heightened alertness. The student’s reaction to the near-miss accident fits this description perfectly.
Choice D Reason:
The stage of resistance is the second phase of the general adaptation syndrome. During this stage, the body attempts to adapt to the stressor and return to a state of balance. If the stressor persists, the body remains on high alert, but the initial shock of the alarm stage has passed. Since the student’s response is immediate and acute, it aligns with the alarm stage rather than the resistance stage.
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