Which hormone primarily regulates sodium reabsorption in the kidneys?

Correct Answer: C

Rationale: Correct Answer: C (Aldosterone) Rationale: Aldosterone is produced by the adrenal glands and plays a crucial role in regulating sodium reabsorption in the kidneys. It acts on the distal convoluted tubule and collecting ducts to increase sodium reabsorption and potassium excretion, thereby helping to maintain electrolyte balance. In contrast, ADH primarily regulates water reabsorption, ANP promotes sodium excretion, and cortisol is involved in stress response and metabolism, not sodium reabsorption in the kidneys. Therefore, aldosterone is the hormone primarily responsible for regulating sodium reabsorption in the kidneys.

Correct Answer: D

Rationale: The correct answer is D: Increased bicarbonate production. In metabolic acidosis, the body tries to compensate by increasing the production of bicarbonate to neutralize the excess acid. This helps to restore the acid-base balance. Option A is incorrect as increased renal excretion of bicarbonate would worsen metabolic acidosis. Option B, decreased respiratory rate, would not help to compensate for metabolic acidosis as it does not directly address the excess acid. Option C, hyperventilation, is a compensatory mechanism for respiratory acidosis, not metabolic acidosis.

Correct Answer: A

Rationale: The correct answer is A: ANP secretion. When blood volume is low, the body releases atrial natriuretic peptide (ANP) to help maintain blood pressure. ANP causes vasodilation, which decreases blood pressure and increases sodium and water excretion in the urine, ultimately helping to restore blood volume. Rationale: A: ANP secretion directly acts to decrease blood pressure and increase sodium and water excretion. B: RAAS activation would actually increase blood pressure and retain sodium and water, opposing the goal of maintaining blood pressure when blood volume is low. C: Increased urination alone may not effectively restore blood volume, especially if it leads to further dehydration. D: Decreased ADH secretion would lead to increased urine output but may not be as effective as ANP in restoring blood volume and maintaining blood pressure.

Correct Answer: A

Rationale: The correct diagnosis is A: Respiratory alkalosis. In this case, the patient has a high pH (alkalosis) and low PaCO₂ (hypocapnia), indicating respiratory alkalosis. Rapid breathing leads to excessive CO₂ elimination, causing a decrease in PaCO₂ and subsequent alkalosis. Choice B (Respiratory acidosis) is incorrect as the PaCO₂ is low, not high. Choice C (Metabolic alkalosis) is incorrect as the primary disturbance is respiratory, not metabolic. Choice D (Metabolic acidosis) is incorrect as the pH is elevated, not decreased.

Correct Answer: B

Rationale: The correct answer is B: Loss of bicarbonate. Severe diarrhea leads to loss of bicarbonate-rich fluids, causing metabolic acidosis. Bicarbonate is a major buffer in the body, helping to maintain pH balance. Loss of potassium (A) is more likely to cause metabolic alkalosis. Retention of hydrogen ions (C) would cause metabolic acidosis but is not the primary issue in this scenario. Retention of bicarbonate (D) would actually help correct the acidosis, not cause it.