Memmler's Structure and Function of the Human
Body, 12th Edition - Cohen | Complete Test Bank with
Answers
1. A researcher is studying a newly discovered ion channel that is permeable to both Na+ and K+
but not to Ca2+. In a neuron at rest, the membrane potential is -70 mV. The equilibrium potentials
for Na+ and K+ are +60 mV and -90 mV, respectively. If the channel opens, which of the following
best describes the resulting change in membrane potential?
A. It will depolarize toward +60 mV.
B. It will hyperpolarize toward -90 mV.
C. It will move toward an intermediate potential between -90 mV and +60 mV.
D. It will remain at -70 mV because the net current is zero.
Answer: C
Rationale: When a channel permeable to both Na+ and K+ opens, the membrane potential moves toward
the reversal potential determined by the relative permeabilities and concentration gradients. Since both
ions have driving forces in opposite directions, the potential will settle at a value between E_Na and
E_K, typically near 0 mV, but not exactly at either equilibrium. Option A is incorrect because K+ efflux
opposes full depolarization. Option B ignores Na+ influx. Option D would only occur if the channel
were selectively permeable to both equally and at rest, but net current is not zero until the reversal
potential is reached.
2. In a patient with a complete transection of the spinal cord at the T10 level, which of the
following clinical findings is most likely to be observed immediately after injury?
A. Flaccid paralysis below the lesion and loss of reflexes.
B. Spastic paralysis below the lesion and hyperreflexia.
C. Loss of sensation on the contralateral side below the lesion.
D. Intact autonomic function below the lesion.
Answer: A
Rationale: Spinal shock occurs immediately after complete transection, causing flaccid paralysis and
areflexia below the level of injury due to loss of descending facilitatory input. Spasticity and
hyperreflexia (option B) develop weeks to months later after spinal shock resolves. Option C describes
contralateral loss of pain and temperature (spinothalamic tract) but not typical for complete lesion.
Option D is incorrect because autonomic function is disrupted, leading to loss of vasomotor tone and
bowel/bladder control.
3. Which of the following best explains why the oxygen-hemoglobin dissociation curve shifts to the
right during exercise?
A. Increased pH in active tissues decreases hemoglobin's affinity for oxygen.
Page 1
,B. Increased temperature and 2,3-BPG levels decrease hemoglobin's affinity for oxygen.
C. Decreased CO2 levels increase hemoglobin's affinity for oxygen.
D. Increased oxygen partial pressure in tissues promotes unloading.
Answer: B
Rationale: During exercise, active muscles produce heat and 2,3-BPG, and become more acidic (due to
lactic acid and CO2). These factors decrease hemoglobin's affinity for oxygen, shifting the curve right
and facilitating oxygen unloading. Option A is incorrect because pH decreases (acidosis), not increases.
Option C is wrong because CO2 increases. Option D misstates the cause; increased oxygen partial
pressure would actually shift the curve left.
4. A researcher measures glomerular filtration rate (GFR) using inulin clearance. If the plasma
inulin concentration is 0.5 mg/mL and urine inulin concentration is 30 mg/mL with a urine flow
rate of 2 mL/min, what is the GFR?
A. 60 mL/min
B. 120 mL/min
C. 150 mL/min
D. 180 mL/min
Answer: B
Rationale: GFR = (urine concentration × urine flow rate) / plasma concentration = (30 mg/mL × 2
mL/min) / 0.5 mg/mL = .5 = 120 mL/min. Option A is half the correct value (if flow rate was 1
mL/min). Option C would require plasma inulin of 0.4 mg/mL. Option D would require plasma inulin of
0.33 mg/mL.
5. Which of the following best describes the role of the juxtaglomerular apparatus in regulating
blood pressure?
A. Macula densa cells detect low NaCl and stimulate renin release from granular cells.
B. Granular cells detect low blood pressure directly and release angiotensinogen.
C. Macula densa cells release renin in response to high blood pressure.
D. Granular cells secrete erythropoietin in response to hypoxia.
Answer: A
Rationale: The juxtaglomerular apparatus includes macula densa cells that sense decreased NaCl
delivery (often due to low GFR) and signal granular cells to release renin. Renin converts
angiotensinogen to angiotensin I, initiating the RAAS to raise blood pressure. Option B is wrong
because granular cells respond to sympathetic stimulation and low stretch, not directly to low BP, and
they release renin, not angiotensinogen. Option C is incorrect; high NaCl inhibits renin. Option D
describes peritubular capillary fibroblasts, not granular cells.
6. A patient with a deficiency in pancreatic lipase would have the most difficulty digesting which of
the following?
A. Starch
B. Protein
C. Triglycerides
D. Cellulose
Page 2
,Answer: C
Rationale: Pancreatic lipase is essential for breaking down dietary triglycerides into monoglycerides and
fatty acids. Starch digestion begins with salivary amylase and continues with pancreatic amylase (option
A). Protein digestion involves pepsin and pancreatic proteases (option B). Cellulose is not digestible by
humans due to lack of cellulase (option D).
7. Which of the following statements about the structure of the alveoli is most accurate?
A. Type I pneumocytes produce surfactant to reduce surface tension.
B. Type II pneumocytes are the primary site of gas exchange.
C. Alveolar macrophages are found within the interstitium.
D. The alveolar epithelium is composed mainly of squamous cells.
Answer: D
Rationale: Alveoli are lined mainly by type I pneumocytes, which are squamous epithelial cells that
facilitate gas exchange. Type II pneumocytes produce surfactant (option A is wrong). Gas exchange
occurs across type I cells, not type II (option B). Alveolar macrophages are located on the alveolar
surface, not in the interstitium (option C).
8. In a patient with hypoparathyroidism, which of the following laboratory findings is most likely?
A. Hypercalcemia and hypophosphatemia
B. Hypocalcemia and hyperphosphatemia
C. Hypercalcemia and hyperphosphatemia
D. Hypocalcemia and hypophosphatemia
Answer: B
Rationale: Parathyroid hormone (PTH) increases serum calcium and decreases serum phosphate by
acting on bone, kidneys, and intestines. In hypoparathyroidism, lack of PTH leads to low calcium and
high phosphate. Option A is seen in hyperparathyroidism. Options C and D are not typical.
9. Which of the following best describes the effect of aldosterone on the distal convoluted tubule?
A. It increases Na+ reabsorption and K+ secretion by upregulating Na+/K+ ATPase and ENaC.
B. It increases H+ secretion by activating the H+/K+ ATPase.
C. It decreases water reabsorption by downregulating aquaporins.
D. It increases Ca2+ reabsorption by stimulating TRPV5 channels.
Answer: A
Rationale: Aldosterone binds to mineralocorticoid receptors in principal cells of the distal tubule and
collecting duct, increasing expression of Na+ channels (ENaC) and Na+/K+ ATPase, leading to
enhanced Na+ reabsorption and K+ secretion. Option B describes intercalated cells and is not a direct
aldosterone effect. Option C is opposite; aldosterone can increase water reabsorption indirectly via Na+
reabsorption. Option D involves PTH and vitamin D, not aldosterone.
10. A patient with a tumor in the adrenal medulla would most likely present with which of the
following symptoms?
A. Hypoglycemia and bradycardia
Page 3
, B. Hypertension and tachycardia
C. Hyperkalemia and metabolic acidosis
D. Hypercalcemia and polyuria
Answer: B
Rationale: Adrenal medullary tumors (pheochromocytomas) secrete catecholamines (epinephrine and
norepinephrine), causing episodic hypertension, tachycardia, sweating, and anxiety. Hypoglycemia
(option A) is associated with insulinoma. Hyperkalemia and metabolic acidosis (option C) suggest
adrenal insufficiency (Addisonian crisis). Hypercalcemia and polyuria (option D) are seen in
hyperparathyroidism.
11. In a study of calcium homeostasis, a patient with chronic kidney disease presents with
hypocalcemia. Which of the following best explains the failure of parathyroid hormone (PTH) to
correct the serum calcium level in this setting?
A. PTH secretion is inhibited by the low serum calcium.
B. PTH receptors in bone are downregulated due to uremic toxins.
C. The kidneys cannot convert 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D, reducing intestinal calcium
absorption.
D. PTH increases renal phosphate reabsorption, worsening hypocalcemia.
Answer: C
Rationale: In chronic kidney disease, impaired renal 1±-hydroxylase activity reduces calcitriol
production, decreasing intestinal calcium absorption despite elevated PTH. PTH secretion increases in
response to hypocalcemia, not inhibition (A). PTH receptors are not typically downregulated by uremia
(B). PTH decreases renal phosphate reabsorption, not increases (D).
12. A researcher is investigating the effect of a novel drug on synaptic transmission. The drug is
found to block voltage-gated calcium channels on the presynaptic terminal. Which of the following
immediate effects is most likely to be observed at the neuromuscular junction?
A. Increased frequency of miniature end-plate potentials.
B. Decreased amplitude of end-plate potentials without change in frequency.
C. Complete absence of both miniature and evoked end-plate potentials.
D. Prolonged duration of end-plate potentials due to delayed acetylcholine degradation.
Answer: B
Rationale: Blocking presynaptic calcium channels reduces calcium influx, decreasing the probability of
vesicle fusion and thus the quantal content (number of vesicles released per action potential), reducing
end-plate potential amplitude. Miniature end-plate potentials (spontaneous single vesicle releases) are
unaffected in frequency because they do not require calcium influx, but their amplitude remains normal
(A, C). Prolonged duration (D) would result from acetylcholinesterase inhibition, not calcium channel
block.
13. Which of the following best describes the role of the arcuate nucleus of the hypothalamus in the
regulation of energy balance?
A. It integrates signals from the vagus nerve to control gastric emptying.
Page 4
Body, 12th Edition - Cohen | Complete Test Bank with
Answers
1. A researcher is studying a newly discovered ion channel that is permeable to both Na+ and K+
but not to Ca2+. In a neuron at rest, the membrane potential is -70 mV. The equilibrium potentials
for Na+ and K+ are +60 mV and -90 mV, respectively. If the channel opens, which of the following
best describes the resulting change in membrane potential?
A. It will depolarize toward +60 mV.
B. It will hyperpolarize toward -90 mV.
C. It will move toward an intermediate potential between -90 mV and +60 mV.
D. It will remain at -70 mV because the net current is zero.
Answer: C
Rationale: When a channel permeable to both Na+ and K+ opens, the membrane potential moves toward
the reversal potential determined by the relative permeabilities and concentration gradients. Since both
ions have driving forces in opposite directions, the potential will settle at a value between E_Na and
E_K, typically near 0 mV, but not exactly at either equilibrium. Option A is incorrect because K+ efflux
opposes full depolarization. Option B ignores Na+ influx. Option D would only occur if the channel
were selectively permeable to both equally and at rest, but net current is not zero until the reversal
potential is reached.
2. In a patient with a complete transection of the spinal cord at the T10 level, which of the
following clinical findings is most likely to be observed immediately after injury?
A. Flaccid paralysis below the lesion and loss of reflexes.
B. Spastic paralysis below the lesion and hyperreflexia.
C. Loss of sensation on the contralateral side below the lesion.
D. Intact autonomic function below the lesion.
Answer: A
Rationale: Spinal shock occurs immediately after complete transection, causing flaccid paralysis and
areflexia below the level of injury due to loss of descending facilitatory input. Spasticity and
hyperreflexia (option B) develop weeks to months later after spinal shock resolves. Option C describes
contralateral loss of pain and temperature (spinothalamic tract) but not typical for complete lesion.
Option D is incorrect because autonomic function is disrupted, leading to loss of vasomotor tone and
bowel/bladder control.
3. Which of the following best explains why the oxygen-hemoglobin dissociation curve shifts to the
right during exercise?
A. Increased pH in active tissues decreases hemoglobin's affinity for oxygen.
Page 1
,B. Increased temperature and 2,3-BPG levels decrease hemoglobin's affinity for oxygen.
C. Decreased CO2 levels increase hemoglobin's affinity for oxygen.
D. Increased oxygen partial pressure in tissues promotes unloading.
Answer: B
Rationale: During exercise, active muscles produce heat and 2,3-BPG, and become more acidic (due to
lactic acid and CO2). These factors decrease hemoglobin's affinity for oxygen, shifting the curve right
and facilitating oxygen unloading. Option A is incorrect because pH decreases (acidosis), not increases.
Option C is wrong because CO2 increases. Option D misstates the cause; increased oxygen partial
pressure would actually shift the curve left.
4. A researcher measures glomerular filtration rate (GFR) using inulin clearance. If the plasma
inulin concentration is 0.5 mg/mL and urine inulin concentration is 30 mg/mL with a urine flow
rate of 2 mL/min, what is the GFR?
A. 60 mL/min
B. 120 mL/min
C. 150 mL/min
D. 180 mL/min
Answer: B
Rationale: GFR = (urine concentration × urine flow rate) / plasma concentration = (30 mg/mL × 2
mL/min) / 0.5 mg/mL = .5 = 120 mL/min. Option A is half the correct value (if flow rate was 1
mL/min). Option C would require plasma inulin of 0.4 mg/mL. Option D would require plasma inulin of
0.33 mg/mL.
5. Which of the following best describes the role of the juxtaglomerular apparatus in regulating
blood pressure?
A. Macula densa cells detect low NaCl and stimulate renin release from granular cells.
B. Granular cells detect low blood pressure directly and release angiotensinogen.
C. Macula densa cells release renin in response to high blood pressure.
D. Granular cells secrete erythropoietin in response to hypoxia.
Answer: A
Rationale: The juxtaglomerular apparatus includes macula densa cells that sense decreased NaCl
delivery (often due to low GFR) and signal granular cells to release renin. Renin converts
angiotensinogen to angiotensin I, initiating the RAAS to raise blood pressure. Option B is wrong
because granular cells respond to sympathetic stimulation and low stretch, not directly to low BP, and
they release renin, not angiotensinogen. Option C is incorrect; high NaCl inhibits renin. Option D
describes peritubular capillary fibroblasts, not granular cells.
6. A patient with a deficiency in pancreatic lipase would have the most difficulty digesting which of
the following?
A. Starch
B. Protein
C. Triglycerides
D. Cellulose
Page 2
,Answer: C
Rationale: Pancreatic lipase is essential for breaking down dietary triglycerides into monoglycerides and
fatty acids. Starch digestion begins with salivary amylase and continues with pancreatic amylase (option
A). Protein digestion involves pepsin and pancreatic proteases (option B). Cellulose is not digestible by
humans due to lack of cellulase (option D).
7. Which of the following statements about the structure of the alveoli is most accurate?
A. Type I pneumocytes produce surfactant to reduce surface tension.
B. Type II pneumocytes are the primary site of gas exchange.
C. Alveolar macrophages are found within the interstitium.
D. The alveolar epithelium is composed mainly of squamous cells.
Answer: D
Rationale: Alveoli are lined mainly by type I pneumocytes, which are squamous epithelial cells that
facilitate gas exchange. Type II pneumocytes produce surfactant (option A is wrong). Gas exchange
occurs across type I cells, not type II (option B). Alveolar macrophages are located on the alveolar
surface, not in the interstitium (option C).
8. In a patient with hypoparathyroidism, which of the following laboratory findings is most likely?
A. Hypercalcemia and hypophosphatemia
B. Hypocalcemia and hyperphosphatemia
C. Hypercalcemia and hyperphosphatemia
D. Hypocalcemia and hypophosphatemia
Answer: B
Rationale: Parathyroid hormone (PTH) increases serum calcium and decreases serum phosphate by
acting on bone, kidneys, and intestines. In hypoparathyroidism, lack of PTH leads to low calcium and
high phosphate. Option A is seen in hyperparathyroidism. Options C and D are not typical.
9. Which of the following best describes the effect of aldosterone on the distal convoluted tubule?
A. It increases Na+ reabsorption and K+ secretion by upregulating Na+/K+ ATPase and ENaC.
B. It increases H+ secretion by activating the H+/K+ ATPase.
C. It decreases water reabsorption by downregulating aquaporins.
D. It increases Ca2+ reabsorption by stimulating TRPV5 channels.
Answer: A
Rationale: Aldosterone binds to mineralocorticoid receptors in principal cells of the distal tubule and
collecting duct, increasing expression of Na+ channels (ENaC) and Na+/K+ ATPase, leading to
enhanced Na+ reabsorption and K+ secretion. Option B describes intercalated cells and is not a direct
aldosterone effect. Option C is opposite; aldosterone can increase water reabsorption indirectly via Na+
reabsorption. Option D involves PTH and vitamin D, not aldosterone.
10. A patient with a tumor in the adrenal medulla would most likely present with which of the
following symptoms?
A. Hypoglycemia and bradycardia
Page 3
, B. Hypertension and tachycardia
C. Hyperkalemia and metabolic acidosis
D. Hypercalcemia and polyuria
Answer: B
Rationale: Adrenal medullary tumors (pheochromocytomas) secrete catecholamines (epinephrine and
norepinephrine), causing episodic hypertension, tachycardia, sweating, and anxiety. Hypoglycemia
(option A) is associated with insulinoma. Hyperkalemia and metabolic acidosis (option C) suggest
adrenal insufficiency (Addisonian crisis). Hypercalcemia and polyuria (option D) are seen in
hyperparathyroidism.
11. In a study of calcium homeostasis, a patient with chronic kidney disease presents with
hypocalcemia. Which of the following best explains the failure of parathyroid hormone (PTH) to
correct the serum calcium level in this setting?
A. PTH secretion is inhibited by the low serum calcium.
B. PTH receptors in bone are downregulated due to uremic toxins.
C. The kidneys cannot convert 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D, reducing intestinal calcium
absorption.
D. PTH increases renal phosphate reabsorption, worsening hypocalcemia.
Answer: C
Rationale: In chronic kidney disease, impaired renal 1±-hydroxylase activity reduces calcitriol
production, decreasing intestinal calcium absorption despite elevated PTH. PTH secretion increases in
response to hypocalcemia, not inhibition (A). PTH receptors are not typically downregulated by uremia
(B). PTH decreases renal phosphate reabsorption, not increases (D).
12. A researcher is investigating the effect of a novel drug on synaptic transmission. The drug is
found to block voltage-gated calcium channels on the presynaptic terminal. Which of the following
immediate effects is most likely to be observed at the neuromuscular junction?
A. Increased frequency of miniature end-plate potentials.
B. Decreased amplitude of end-plate potentials without change in frequency.
C. Complete absence of both miniature and evoked end-plate potentials.
D. Prolonged duration of end-plate potentials due to delayed acetylcholine degradation.
Answer: B
Rationale: Blocking presynaptic calcium channels reduces calcium influx, decreasing the probability of
vesicle fusion and thus the quantal content (number of vesicles released per action potential), reducing
end-plate potential amplitude. Miniature end-plate potentials (spontaneous single vesicle releases) are
unaffected in frequency because they do not require calcium influx, but their amplitude remains normal
(A, C). Prolonged duration (D) would result from acetylcholinesterase inhibition, not calcium channel
block.
13. Which of the following best describes the role of the arcuate nucleus of the hypothalamus in the
regulation of energy balance?
A. It integrates signals from the vagus nerve to control gastric emptying.
Page 4
