BIO 336 Exam 3 Principles of Human Physiology
Questions with Answers| San Diego State University|
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1. What is the functional unit of the kidney?
A. The renal pyramid
B. The glomerulus alone
C. The nephron, consisting of a renal corpuscle and a renal tubule
D. The renal pelvis
Answer: C
Rationale: Each kidney contains about one million nephrons. Each nephron has a
renal corpuscle (glomerulus plus Bowman's capsule) that filters plasma, and a
tubule (proximal tubule, loop of Henle, distal tubule) that modifies the filtrate
before it drains into a collecting duct.
2. Which structures make up the glomerular filtration barrier, from blood to
Bowman's space?
A. Fenestrated capillary endothelium, the basement membrane, and podocyte
filtration slits
B. Tight-junction endothelium, smooth muscle, and epithelial cells
C. The proximal tubule epithelium and brush border
D. Peritubular capillaries and the vasa recta
Answer: A
Rationale: Fluid passes through pores in the endothelium, a negatively charged
basement membrane, and slit diaphragms between podocyte foot processes. Size
and charge together determine what is filtered.
3. Why is albumin normally almost absent from the glomerular filtrate?
A. It is actively secreted back into the blood by podocytes
B. It is fully reabsorbed by the loop of Henle
C. It is smaller than the filtration pores but is destroyed in Bowman's space
D. Its large size and negative charge cause it to be repelled by the negatively
charged basement membrane and filtration slits
,Answer: D
Rationale: Albumin (about 69 kDa) is at the limit of filterability and is anionic, so it
is largely excluded. Proteinuria signals damage to the filtration barrier, as in
diabetic nephropathy or glomerulonephritis.
4. Approximately what is the normal glomerular filtration rate (GFR) in a healthy
adult?
A. About 1.5 mL/min
B. About 125 mL/min (roughly 180 L/day)
C. About 12.5 mL/min
D. About 1,250 mL/min
Answer: B
Rationale: Roughly 180 L of plasma is filtered each day, yet only about 1.5 L of
urine is produced, so more than 99% of the filtered water is reabsorbed.
5. In the glomerulus, PGC = 55 mmHg, Bowman's capsule hydrostatic pressure =
15 mmHg, and glomerular capillary oncotic pressure = 30 mmHg. What is the net
filtration pressure?
A. 40 mmHg
B. 70 mmHg
C. 10 mmHg
D. 25 mmHg
Answer: C
Rationale: Net filtration pressure = PGC - (PBS + oncotic pressure) = 55 - (15 + 30)
= 10 mmHg, favoring filtration.
6. A kidney stone obstructs the ureter, raising pressure upstream in Bowman's
capsule. What is the effect on GFR?
A. GFR decreases because increased capsule hydrostatic pressure opposes
filtration
B. GFR increases because filtration is unopposed
C. GFR is unchanged
D. GFR increases because oncotic pressure falls
Answer: A
,Rationale: Bowman's capsule hydrostatic pressure opposes filtration. When
urinary outflow is blocked, back pressure rises, net filtration pressure falls, and
GFR declines.
7. How does constriction of the afferent arteriole change glomerular capillary
pressure and GFR?
A. Both increase, because resistance upstream raises pressure
B. Pressure increases and GFR decreases
C. Pressure and GFR are unchanged
D. Both decrease, because less blood enters the glomerulus
Answer: D
Rationale: Constricting the afferent arteriole reduces inflow and lowers
hydrostatic pressure in the glomerulus. Moderate efferent arteriolar constriction,
by contrast, raises glomerular pressure and GFR.
8. How does moderate constriction of the efferent arteriole (e.g., by angiotensin
II) affect GFR?
A. It decreases GFR by reducing inflow
B. It increases GFR by raising glomerular capillary hydrostatic pressure
C. It has no effect on GFR
D. It abolishes filtration immediately
Answer: B
Rationale: Resistance downstream of the glomerulus backs up blood and raises
capillary pressure. This helps maintain GFR when arterial pressure falls, which is
why ACE inhibitors can reduce GFR in patients with renal artery stenosis.
9. Which mechanism allows renal blood flow and GFR to remain relatively
constant when mean arterial pressure varies between about 80 and 180 mmHg?
A. Sympathetic vasoconstriction of all renal vessels
B. Continuous release of aldosterone
C. Renal autoregulation through the myogenic response and tubuloglomerular
feedback
D. Direct vagal control of the glomerulus
Answer: C
, Rationale: Vascular smooth muscle in the afferent arteriole contracts when
stretched by higher pressure (myogenic response), and the macula densa senses
tubular NaCl delivery and adjusts afferent tone (tubuloglomerular feedback).
10. The macula densa detects increased NaCl delivery in the distal tubule. What
is the response?
A. Paracrine signals constrict the afferent arteriole, reducing GFR to lower
filtered NaCl delivery
B. The afferent arteriole dilates, increasing GFR
C. Aldosterone secretion increases immediately
D. Antidiuretic hormone is released
Answer: A
Rationale: This tubuloglomerular feedback matches filtration to the tubule's
capacity to reabsorb. High flow signals excess filtration, so GFR is reduced. Low
delivery causes dilation and renin release.
11. Which cells secrete renin, and what is the stimulus?
A. Podocytes, in response to high glucose
B. Proximal tubule cells, in response to high urea
C. Principal cells, in response to ADH
D. Juxtaglomerular cells of the afferent arteriole, in response to low renal
perfusion pressure, sympathetic stimulation, or low NaCl at the macula densa
Answer: D
Rationale: Renin initiates the RAAS: it converts angiotensinogen to angiotensin I,
which ACE converts to angiotensin II, causing vasoconstriction and aldosterone
release.
12. What fraction of cardiac output do the kidneys normally receive?
A. About 2%
B. About 20-25%
C. About 50%
D. About 70%
Answer: B
Rationale: Despite weighing less than 1% of body mass, the kidneys receive about
1.1 L/min of blood. This high flow supports filtration rather than metabolic needs.
Questions with Answers| San Diego State University|
Pass Guaranteed
1. What is the functional unit of the kidney?
A. The renal pyramid
B. The glomerulus alone
C. The nephron, consisting of a renal corpuscle and a renal tubule
D. The renal pelvis
Answer: C
Rationale: Each kidney contains about one million nephrons. Each nephron has a
renal corpuscle (glomerulus plus Bowman's capsule) that filters plasma, and a
tubule (proximal tubule, loop of Henle, distal tubule) that modifies the filtrate
before it drains into a collecting duct.
2. Which structures make up the glomerular filtration barrier, from blood to
Bowman's space?
A. Fenestrated capillary endothelium, the basement membrane, and podocyte
filtration slits
B. Tight-junction endothelium, smooth muscle, and epithelial cells
C. The proximal tubule epithelium and brush border
D. Peritubular capillaries and the vasa recta
Answer: A
Rationale: Fluid passes through pores in the endothelium, a negatively charged
basement membrane, and slit diaphragms between podocyte foot processes. Size
and charge together determine what is filtered.
3. Why is albumin normally almost absent from the glomerular filtrate?
A. It is actively secreted back into the blood by podocytes
B. It is fully reabsorbed by the loop of Henle
C. It is smaller than the filtration pores but is destroyed in Bowman's space
D. Its large size and negative charge cause it to be repelled by the negatively
charged basement membrane and filtration slits
,Answer: D
Rationale: Albumin (about 69 kDa) is at the limit of filterability and is anionic, so it
is largely excluded. Proteinuria signals damage to the filtration barrier, as in
diabetic nephropathy or glomerulonephritis.
4. Approximately what is the normal glomerular filtration rate (GFR) in a healthy
adult?
A. About 1.5 mL/min
B. About 125 mL/min (roughly 180 L/day)
C. About 12.5 mL/min
D. About 1,250 mL/min
Answer: B
Rationale: Roughly 180 L of plasma is filtered each day, yet only about 1.5 L of
urine is produced, so more than 99% of the filtered water is reabsorbed.
5. In the glomerulus, PGC = 55 mmHg, Bowman's capsule hydrostatic pressure =
15 mmHg, and glomerular capillary oncotic pressure = 30 mmHg. What is the net
filtration pressure?
A. 40 mmHg
B. 70 mmHg
C. 10 mmHg
D. 25 mmHg
Answer: C
Rationale: Net filtration pressure = PGC - (PBS + oncotic pressure) = 55 - (15 + 30)
= 10 mmHg, favoring filtration.
6. A kidney stone obstructs the ureter, raising pressure upstream in Bowman's
capsule. What is the effect on GFR?
A. GFR decreases because increased capsule hydrostatic pressure opposes
filtration
B. GFR increases because filtration is unopposed
C. GFR is unchanged
D. GFR increases because oncotic pressure falls
Answer: A
,Rationale: Bowman's capsule hydrostatic pressure opposes filtration. When
urinary outflow is blocked, back pressure rises, net filtration pressure falls, and
GFR declines.
7. How does constriction of the afferent arteriole change glomerular capillary
pressure and GFR?
A. Both increase, because resistance upstream raises pressure
B. Pressure increases and GFR decreases
C. Pressure and GFR are unchanged
D. Both decrease, because less blood enters the glomerulus
Answer: D
Rationale: Constricting the afferent arteriole reduces inflow and lowers
hydrostatic pressure in the glomerulus. Moderate efferent arteriolar constriction,
by contrast, raises glomerular pressure and GFR.
8. How does moderate constriction of the efferent arteriole (e.g., by angiotensin
II) affect GFR?
A. It decreases GFR by reducing inflow
B. It increases GFR by raising glomerular capillary hydrostatic pressure
C. It has no effect on GFR
D. It abolishes filtration immediately
Answer: B
Rationale: Resistance downstream of the glomerulus backs up blood and raises
capillary pressure. This helps maintain GFR when arterial pressure falls, which is
why ACE inhibitors can reduce GFR in patients with renal artery stenosis.
9. Which mechanism allows renal blood flow and GFR to remain relatively
constant when mean arterial pressure varies between about 80 and 180 mmHg?
A. Sympathetic vasoconstriction of all renal vessels
B. Continuous release of aldosterone
C. Renal autoregulation through the myogenic response and tubuloglomerular
feedback
D. Direct vagal control of the glomerulus
Answer: C
, Rationale: Vascular smooth muscle in the afferent arteriole contracts when
stretched by higher pressure (myogenic response), and the macula densa senses
tubular NaCl delivery and adjusts afferent tone (tubuloglomerular feedback).
10. The macula densa detects increased NaCl delivery in the distal tubule. What
is the response?
A. Paracrine signals constrict the afferent arteriole, reducing GFR to lower
filtered NaCl delivery
B. The afferent arteriole dilates, increasing GFR
C. Aldosterone secretion increases immediately
D. Antidiuretic hormone is released
Answer: A
Rationale: This tubuloglomerular feedback matches filtration to the tubule's
capacity to reabsorb. High flow signals excess filtration, so GFR is reduced. Low
delivery causes dilation and renin release.
11. Which cells secrete renin, and what is the stimulus?
A. Podocytes, in response to high glucose
B. Proximal tubule cells, in response to high urea
C. Principal cells, in response to ADH
D. Juxtaglomerular cells of the afferent arteriole, in response to low renal
perfusion pressure, sympathetic stimulation, or low NaCl at the macula densa
Answer: D
Rationale: Renin initiates the RAAS: it converts angiotensinogen to angiotensin I,
which ACE converts to angiotensin II, causing vasoconstriction and aldosterone
release.
12. What fraction of cardiac output do the kidneys normally receive?
A. About 2%
B. About 20-25%
C. About 50%
D. About 70%
Answer: B
Rationale: Despite weighing less than 1% of body mass, the kidneys receive about
1.1 L/min of blood. This high flow supports filtration rather than metabolic needs.
