, Question 1
A researcher isolates a novel cell line and observes that a specific ion channel
opens in response to mechanical deformation of the plasma membrane,
allowing K+ efflux. Which of the following best describes the gating
mechanism and its immediate effect on the membrane potential?
A. Voltage-gated; depolarization due to K+ influx
B. Ligand-gated; hyperpolarization due to K+ efflux
C. Mechanically gated; hyperpolarization due to K+ efflux
D. Mechanically gated; depolarization due to K+ efflux
Correct Answer: C - Mechanically gated; hyperpolarization due
to K+ efflux
RATIONALE
Mechanical deformation directly gates the channel. Since K+ is more
concentrated inside the cell, efflux of K+ makes the inside more
negative, causing hyperpolarization. Thus, the correct answer is C.
Question 2
In a patient with severe liver failure, plasma protein synthesis is markedly
reduced. Which of the following Starling forces would be most directly
affected, and what is the predicted consequence?
A. Increased capillary hydrostatic pressure, leading to edema
B. Decreased plasma colloid osmotic pressure, leading to edema
C. Increased interstitial colloid osmotic pressure, leading to dehydration
D. Decreased capillary hydrostatic pressure, leading to dehydration
Correct Answer: B - Decreased plasma colloid osmotic pressure,
leading to edema
Page 2
, RATIONALE
Liver failure reduces albumin synthesis, lowering plasma colloid
osmotic pressure. This decreases the force pulling fluid back into
capillaries, causing fluid accumulation in the interstitium (edema).
Thus, B is correct.
Question 3
During a marathon, a runner's core body temperature rises. Which of the
following integumentary responses is primarily responsible for dissipating heat
via evaporative cooling, and what is the role of the autonomic nervous system
in this process?
A. Vasoconstriction of dermal arterioles; sympathetic cholinergic
stimulation
B. Vasodilation of dermal arterioles and secretion of sweat; sympathetic
cholinergic stimulation
C. Vasodilation of dermal arterioles and secretion of sweat;
parasympathetic cholinergic stimulation
D. Vasoconstriction of dermal arterioles; parasympathetic cholinergic
stimulation
Correct Answer: B - Vasodilation of dermal arterioles and
secretion of sweat; sympathetic cholinergic stimulation
RATIONALE
Evaporative cooling requires sweat secretion and increased skin blood
flow via vasodilation. These are mediated by sympathetic cholinergic
fibers. Thus, B is correct.
Question 4
A mutation in the gene encoding collagen type I leads to brittle bones. Which
of the following best explains the molecular basis for this condition?
A. Defective collagen cross-linking reduces tensile strength of bone.
Page 3
, B. Impaired hydroxyapatite crystal formation leads to soft bones.
C. Increased osteoclast activity causes excessive bone resorption.
D. Defective collagen synthesis impairs osteoid formation, leading to
weak bone matrix.
Correct Answer: D - Defective collagen synthesis impairs osteoid
formation, leading to weak bone matrix.
RATIONALE
Collagen type I is the main organic component of bone matrix.
Mutations impair osteoid formation, resulting in brittle bones
(osteogenesis imperfecta). Thus, D is correct.
Question 5
In a laboratory experiment, a skeletal muscle fiber is stimulated with a single
action potential, then a second action potential is applied during the relaxation
phase. What is the expected mechanical response?
A. No additional contraction due to the refractory period
B. A second contraction of equal magnitude, summing to a larger force
C. A second contraction that is weaker due to fatigue
D. Complete tetanus due to sustained calcium release
Correct Answer: B - A second contraction of equal magnitude,
summing to a larger force
RATIONALE
Stimulating during the relaxation phase allows for wave summation,
where the second contraction adds to the first, producing greater force.
Thus, B is correct.
Question 6
A drug that blocks voltage-gated sodium channels in the axon hillock would
most directly affect which aspect of neuronal function?
Page 4
A researcher isolates a novel cell line and observes that a specific ion channel
opens in response to mechanical deformation of the plasma membrane,
allowing K+ efflux. Which of the following best describes the gating
mechanism and its immediate effect on the membrane potential?
A. Voltage-gated; depolarization due to K+ influx
B. Ligand-gated; hyperpolarization due to K+ efflux
C. Mechanically gated; hyperpolarization due to K+ efflux
D. Mechanically gated; depolarization due to K+ efflux
Correct Answer: C - Mechanically gated; hyperpolarization due
to K+ efflux
RATIONALE
Mechanical deformation directly gates the channel. Since K+ is more
concentrated inside the cell, efflux of K+ makes the inside more
negative, causing hyperpolarization. Thus, the correct answer is C.
Question 2
In a patient with severe liver failure, plasma protein synthesis is markedly
reduced. Which of the following Starling forces would be most directly
affected, and what is the predicted consequence?
A. Increased capillary hydrostatic pressure, leading to edema
B. Decreased plasma colloid osmotic pressure, leading to edema
C. Increased interstitial colloid osmotic pressure, leading to dehydration
D. Decreased capillary hydrostatic pressure, leading to dehydration
Correct Answer: B - Decreased plasma colloid osmotic pressure,
leading to edema
Page 2
, RATIONALE
Liver failure reduces albumin synthesis, lowering plasma colloid
osmotic pressure. This decreases the force pulling fluid back into
capillaries, causing fluid accumulation in the interstitium (edema).
Thus, B is correct.
Question 3
During a marathon, a runner's core body temperature rises. Which of the
following integumentary responses is primarily responsible for dissipating heat
via evaporative cooling, and what is the role of the autonomic nervous system
in this process?
A. Vasoconstriction of dermal arterioles; sympathetic cholinergic
stimulation
B. Vasodilation of dermal arterioles and secretion of sweat; sympathetic
cholinergic stimulation
C. Vasodilation of dermal arterioles and secretion of sweat;
parasympathetic cholinergic stimulation
D. Vasoconstriction of dermal arterioles; parasympathetic cholinergic
stimulation
Correct Answer: B - Vasodilation of dermal arterioles and
secretion of sweat; sympathetic cholinergic stimulation
RATIONALE
Evaporative cooling requires sweat secretion and increased skin blood
flow via vasodilation. These are mediated by sympathetic cholinergic
fibers. Thus, B is correct.
Question 4
A mutation in the gene encoding collagen type I leads to brittle bones. Which
of the following best explains the molecular basis for this condition?
A. Defective collagen cross-linking reduces tensile strength of bone.
Page 3
, B. Impaired hydroxyapatite crystal formation leads to soft bones.
C. Increased osteoclast activity causes excessive bone resorption.
D. Defective collagen synthesis impairs osteoid formation, leading to
weak bone matrix.
Correct Answer: D - Defective collagen synthesis impairs osteoid
formation, leading to weak bone matrix.
RATIONALE
Collagen type I is the main organic component of bone matrix.
Mutations impair osteoid formation, resulting in brittle bones
(osteogenesis imperfecta). Thus, D is correct.
Question 5
In a laboratory experiment, a skeletal muscle fiber is stimulated with a single
action potential, then a second action potential is applied during the relaxation
phase. What is the expected mechanical response?
A. No additional contraction due to the refractory period
B. A second contraction of equal magnitude, summing to a larger force
C. A second contraction that is weaker due to fatigue
D. Complete tetanus due to sustained calcium release
Correct Answer: B - A second contraction of equal magnitude,
summing to a larger force
RATIONALE
Stimulating during the relaxation phase allows for wave summation,
where the second contraction adds to the first, producing greater force.
Thus, B is correct.
Question 6
A drug that blocks voltage-gated sodium channels in the axon hillock would
most directly affect which aspect of neuronal function?
Page 4
