What is the primary reason that extracellular fluid volume must be closely regulated?

Correct Answer: A

Rationale: The correct answer is A: to maintain blood pressure. Extracellular fluid volume regulation is crucial for maintaining blood pressure within a normal range. Any imbalance in extracellular fluid volume can lead to changes in blood pressure, potentially causing issues like hypotension or hypertension. Adequate blood pressure is necessary for proper perfusion of organs and tissues. Choice B (to maintain adequate urine formation) is incorrect because extracellular fluid volume regulation primarily affects blood pressure, not urine formation. Choice C (to prevent changes in ICF osmolarity) is incorrect because extracellular fluid volume regulation does not directly impact intracellular fluid osmolarity. Choice D (to prevent cells from swelling or shrinking) is incorrect because intracellular fluid volume regulation, not extracellular fluid volume, is primarily responsible for preventing cellular swelling or shrinking.

Correct Answer: D

Rationale: The correct answer is D: water retention. Water intoxication leads to dilution of electrolytes in the body, causing intracellular fluid (ICF) hypotonicity and circulatory extracellular fluid (ECF) hypotonicity. Excess free water intake can overwhelm the kidneys' ability to excrete it, resulting in hyponatremia. Water retention, on the other hand, implies the body is holding onto water, which is not a characteristic of water intoxication where excess water is typically excreted. Therefore, water retention does not occur during water intoxication.

Correct Answer: D

Rationale: The correct answer is D because when the rate of CO removal by the lungs is less than the rate of CO production by the tissues, more CO builds up in the body. This excess CO leads to increased generation of H+ ions due to the breakdown of CO into H+ ions and carbon. This acidic environment from the increased H+ ions can disrupt the body's pH balance. Choice A is incorrect because the rate of protein catabolism and anabolism does not directly impact the generation of H+ from CO. Choice B is also incorrect because the speed of protein breakdown and synthesis does not affect the generation of H+ from CO. Choice C is incorrect because the rate of CO removal by the lungs being higher than CO production does not lead to an increase in H+ generation.

Correct Answer: B

Rationale: The correct answer is B: Chemical buffer systems respond to changes in acid or base levels. This is because chemical buffer systems work by absorbing or releasing H+ ions to maintain a stable pH in the body. They act immediately to prevent drastic changes in pH levels. A is incorrect because chemical buffer systems act almost instantaneously, not in one to three minutes. C is incorrect because chemical buffer systems do not directly promote H+ excretion by the kidneys; that is the role of the renal system. D is incorrect because chemical buffer systems do not directly stimulate the respiratory center; that is the role of the respiratory system.

Correct Answer: A

Rationale: Step 1: The respiratory system can react to changes in pH quickly due to its ability to modify the rate and depth of breathing. Step 2: By increasing the rate and depth of breathing, excess CO2 is expelled, reducing H+ concentration and restoring pH balance. Step 3: This rapid response allows the respiratory system to buffer against pH changes within seconds. Step 4: Choice A is correct as it accurately describes the buffering activities of the respiratory system. Summary: Choice B is incorrect because an increase in pH would lead to a decrease in H+ concentration, triggering an increase in the depth and rate of breathing. Choice C is incorrect as the respiratory system can buffer against both increases and decreases in arterial [H+]. Choice D is incorrect as the respiratory system can counteract changes in pH from both respiratory and nonrespiratory causes.