,SCI 221 Exam 3 | Human Physiology (2026)
Q&A | Nightingale College
1. Which force primarily drives glomerular filtration in a healthy nephron?
A) Capsular hydrostatic pressure
B) Glomerular capillary hydrostatic pressure
C) Blood colloid osmotic pressure
D) Capsular osmotic pressure
Correct Answer: Glomerular capillary hydrostatic pressure
Rationale: Glomerular capillary hydrostatic pressure is the blood pressure
within the glomerular capillaries that pushes fluid and solutes into Bowman's
capsule. It must overcome the opposing forces of blood colloid osmotic pressure
and capsular hydrostatic pressure to achieve net filtration. This pressure is
maintained at a relatively high level due to the difference in diameter between the
afferent and efferent arterioles.
2. Which portion of the nephron reabsorbs nearly 100% of filtered glucose and
amino acids?
A) Distal convoluted tubule
B) Descending loop of Henle
C) Proximal convoluted tubule
D) Ascending loop of Henle
,Correct Answer: Proximal convoluted tubule
Rationale: The proximal convoluted tubule is the main site for nutrient
reabsorption, reclaiming nearly 100% of filtered glucose and amino acids via
secondary active transport. This process utilizes sodium-linked symporters located
on the brush border of the tubular cells. If blood glucose levels exceed the renal
threshold, these transporters become saturated, resulting in glycosuria.
3. Which hormone increases water permeability of the collecting duct by inserting
aquaporins?
A) Antidiuretic hormone (ADH)
B) Aldosterone
C) Atrial natriuretic peptide (ANP)
D) Parathyroid hormone (PTH)
Correct Answer: Antidiuretic hormone (ADH)
Rationale: ADH, also known as vasopressin, acts on V2 receptors of the
collecting duct to insert aquaporins into the apical membrane. This allows for
significant water reabsorption back into the bloodstream to concentrate the urine.
Without sufficient ADH, the collecting duct remains relatively impermeable to
water, leading to dilute urine output.
4. What is the primary function of the countercurrent multiplier in the loop of
Henle?
A) It prevents the reabsorption of urea into the blood
, B) It actively pumps water out of the ascending limb
C) It creates an osmotic gradient in the renal medulla
D) It decreases the filtration rate at the glomerulus
Correct Answer: It creates an osmotic gradient in the renal medulla
Rationale: The countercurrent multiplier uses energy to create an increasing
osmotic gradient in the medullary interstitium. The ascending limb actively pumps
out salts but is impermeable to water, while the descending limb is permeable to
water but not salts. This gradient is essential for concentrating urine in the
presence of ADH.
5. Which hormone is secreted by the adrenal cortex and promotes sodium
reabsorption and potassium excretion?
A) Aldosterone
B) Cortisol
C) ADH
D) ANP
Correct Answer: Aldosterone
Rationale: Aldosterone, a mineralocorticoid secreted by the adrenal cortex,
promotes sodium reabsorption and potassium excretion in the distal tubule and
collecting duct. Cortisol is a glucocorticoid, ADH regulates water, and ANP
promotes sodium excretion.
6. In which portion of the nephron is water reabsorbed only when ADH is present?
Q&A | Nightingale College
1. Which force primarily drives glomerular filtration in a healthy nephron?
A) Capsular hydrostatic pressure
B) Glomerular capillary hydrostatic pressure
C) Blood colloid osmotic pressure
D) Capsular osmotic pressure
Correct Answer: Glomerular capillary hydrostatic pressure
Rationale: Glomerular capillary hydrostatic pressure is the blood pressure
within the glomerular capillaries that pushes fluid and solutes into Bowman's
capsule. It must overcome the opposing forces of blood colloid osmotic pressure
and capsular hydrostatic pressure to achieve net filtration. This pressure is
maintained at a relatively high level due to the difference in diameter between the
afferent and efferent arterioles.
2. Which portion of the nephron reabsorbs nearly 100% of filtered glucose and
amino acids?
A) Distal convoluted tubule
B) Descending loop of Henle
C) Proximal convoluted tubule
D) Ascending loop of Henle
,Correct Answer: Proximal convoluted tubule
Rationale: The proximal convoluted tubule is the main site for nutrient
reabsorption, reclaiming nearly 100% of filtered glucose and amino acids via
secondary active transport. This process utilizes sodium-linked symporters located
on the brush border of the tubular cells. If blood glucose levels exceed the renal
threshold, these transporters become saturated, resulting in glycosuria.
3. Which hormone increases water permeability of the collecting duct by inserting
aquaporins?
A) Antidiuretic hormone (ADH)
B) Aldosterone
C) Atrial natriuretic peptide (ANP)
D) Parathyroid hormone (PTH)
Correct Answer: Antidiuretic hormone (ADH)
Rationale: ADH, also known as vasopressin, acts on V2 receptors of the
collecting duct to insert aquaporins into the apical membrane. This allows for
significant water reabsorption back into the bloodstream to concentrate the urine.
Without sufficient ADH, the collecting duct remains relatively impermeable to
water, leading to dilute urine output.
4. What is the primary function of the countercurrent multiplier in the loop of
Henle?
A) It prevents the reabsorption of urea into the blood
, B) It actively pumps water out of the ascending limb
C) It creates an osmotic gradient in the renal medulla
D) It decreases the filtration rate at the glomerulus
Correct Answer: It creates an osmotic gradient in the renal medulla
Rationale: The countercurrent multiplier uses energy to create an increasing
osmotic gradient in the medullary interstitium. The ascending limb actively pumps
out salts but is impermeable to water, while the descending limb is permeable to
water but not salts. This gradient is essential for concentrating urine in the
presence of ADH.
5. Which hormone is secreted by the adrenal cortex and promotes sodium
reabsorption and potassium excretion?
A) Aldosterone
B) Cortisol
C) ADH
D) ANP
Correct Answer: Aldosterone
Rationale: Aldosterone, a mineralocorticoid secreted by the adrenal cortex,
promotes sodium reabsorption and potassium excretion in the distal tubule and
collecting duct. Cortisol is a glucocorticoid, ADH regulates water, and ANP
promotes sodium excretion.
6. In which portion of the nephron is water reabsorbed only when ADH is present?
