,BIOL 252 Module 8 | Human Anatomy & Physiology II
w/Lab Exam Q&A | Portage Learning
1. What is the primary function of antidiuretic hormone (ADH) in fluid balance?
A) Increasing sodium reabsorption in the distal tubule
B) Increasing water reabsorption in the collecting duct
C) Promoting potassium excretion in the loop of Henle
D) Stimulating thirst in the hypothalamus
Correct Answer: Increasing water reabsorption in the collecting duct
Rationale: ADH, also known as vasopressin, is released from the posterior pituitary
in response to increased plasma osmolarity or decreased blood volume. It acts on
the collecting ducts of the kidneys to insert aquaporin channels, increasing water
reabsorption and producing concentrated urine. This mechanism is essential for
conserving water during dehydration.
2. Which of the following is the primary cation in the extracellular fluid (ECF)
compartment?
A) Potassium
B) Calcium
C) Sodium
D) Magnesium
Correct Answer: Sodium
,Rationale: Sodium is the most abundant cation in the extracellular fluid, where it is
responsible for maintaining ECF volume and osmolarity. Potassium is the primary
intracellular cation. Calcium and magnesium are important but are present in much
smaller concentrations in the ECF.
3. What is the normal pH range for arterial blood?
A) 7.25 to 7.35
B) 7.35 to 7.45
C) 7.45 to 7.55
D) 7.55 to 7.65
Correct Answer: 7.35 to 7.45
Rationale: The normal pH range for arterial blood is tightly regulated between 7.35
and 7.45. Values below 7.35 indicate acidosis, while values above 7.45 indicate
alkalosis. This narrow range is essential for proper enzyme function, cellular
metabolism, and overall physiological homeostasis.
4. Which buffer system is the most important in the extracellular fluid for maintaining
pH?
A) Phosphate buffer system
B) Protein buffer system
C) Bicarbonate buffer system
D) Ammonia buffer system
, Correct Answer: Bicarbonate buffer system
Rationale: The bicarbonate buffer system is the primary extracellular buffer,
consisting of carbonic acid (H₂CO₃) and bicarbonate ions (HCO₃⁻). It neutralizes acids
and bases to maintain pH within the normal range. The phosphate and protein buffer
systems are also important, but the bicarbonate system is the most significant in the
ECF.
5. What is the primary stimulus for the release of aldosterone?
A) Increased plasma potassium concentration
B) Decreased plasma potassium concentration
C) Increased plasma sodium concentration
D) Decreased plasma osmolarity
Correct Answer: Increased plasma potassium concentration
Rationale: Aldosterone secretion is primarily stimulated by elevated plasma
potassium levels (hyperkalemia) and by activation of the renin-angiotensin-
aldosterone system (RAAS) in response to low blood pressure or low blood volume.
Aldosterone acts on the distal tubule and collecting duct to increase sodium
reabsorption and potassium excretion, thereby restoring electrolyte balance.
6. Which of the following is a cause of respiratory alkalosis?
A) Hypoventilation
B) Hyperventilation
C) Diabetic ketoacidosis
w/Lab Exam Q&A | Portage Learning
1. What is the primary function of antidiuretic hormone (ADH) in fluid balance?
A) Increasing sodium reabsorption in the distal tubule
B) Increasing water reabsorption in the collecting duct
C) Promoting potassium excretion in the loop of Henle
D) Stimulating thirst in the hypothalamus
Correct Answer: Increasing water reabsorption in the collecting duct
Rationale: ADH, also known as vasopressin, is released from the posterior pituitary
in response to increased plasma osmolarity or decreased blood volume. It acts on
the collecting ducts of the kidneys to insert aquaporin channels, increasing water
reabsorption and producing concentrated urine. This mechanism is essential for
conserving water during dehydration.
2. Which of the following is the primary cation in the extracellular fluid (ECF)
compartment?
A) Potassium
B) Calcium
C) Sodium
D) Magnesium
Correct Answer: Sodium
,Rationale: Sodium is the most abundant cation in the extracellular fluid, where it is
responsible for maintaining ECF volume and osmolarity. Potassium is the primary
intracellular cation. Calcium and magnesium are important but are present in much
smaller concentrations in the ECF.
3. What is the normal pH range for arterial blood?
A) 7.25 to 7.35
B) 7.35 to 7.45
C) 7.45 to 7.55
D) 7.55 to 7.65
Correct Answer: 7.35 to 7.45
Rationale: The normal pH range for arterial blood is tightly regulated between 7.35
and 7.45. Values below 7.35 indicate acidosis, while values above 7.45 indicate
alkalosis. This narrow range is essential for proper enzyme function, cellular
metabolism, and overall physiological homeostasis.
4. Which buffer system is the most important in the extracellular fluid for maintaining
pH?
A) Phosphate buffer system
B) Protein buffer system
C) Bicarbonate buffer system
D) Ammonia buffer system
, Correct Answer: Bicarbonate buffer system
Rationale: The bicarbonate buffer system is the primary extracellular buffer,
consisting of carbonic acid (H₂CO₃) and bicarbonate ions (HCO₃⁻). It neutralizes acids
and bases to maintain pH within the normal range. The phosphate and protein buffer
systems are also important, but the bicarbonate system is the most significant in the
ECF.
5. What is the primary stimulus for the release of aldosterone?
A) Increased plasma potassium concentration
B) Decreased plasma potassium concentration
C) Increased plasma sodium concentration
D) Decreased plasma osmolarity
Correct Answer: Increased plasma potassium concentration
Rationale: Aldosterone secretion is primarily stimulated by elevated plasma
potassium levels (hyperkalemia) and by activation of the renin-angiotensin-
aldosterone system (RAAS) in response to low blood pressure or low blood volume.
Aldosterone acts on the distal tubule and collecting duct to increase sodium
reabsorption and potassium excretion, thereby restoring electrolyte balance.
6. Which of the following is a cause of respiratory alkalosis?
A) Hypoventilation
B) Hyperventilation
C) Diabetic ketoacidosis
