BERNE AND LEVY PHYSIOLOGY 7TH EDITION
ACTUAL EXAM QUESTIONS WITH DETAILED
VERIFIED SOLUTIONS
◉2. During the upstroke of the nerve action potential
(A) there is net outward current and the cell interior becomes more
negative
(B) there is net outward current and the cell interior becomes less
negative
(C) there is net inward current and the cell interior becomes more
negative
(D) there is net inward current and the cell interior becomes less
negative . Answer: 2. The answer is D [IV E 1 a, b, 2 b]. During the
upstroke of the action
,potential, the cell depolarizes or becomes less negative. The
depolarization is caused by inward current, which is, by definition, the
movement of positive
charge into the cell. In nerve and in most types of muscle, this inward
current is carried by Na+
◉3. Solutions A and B are separated by a semipermeable membrane that
is
permeable to K+ but not to Cl−. Solution A is 100 mM KCl, and solution
B
is 1 mM KCl. Which of the following statements about solution A and
solution B is true?
(A) K+ ions will diffuse from solution A to solution B until the [K+] of
both
solutions is 50.5 mM
(B) K+ ions will diffuse from solution B to solution A until the [K+] of
both
solutions is 50.5 mM
(C) KCl will diffuse from solution A to solution B until the [KCl] of
both
,solutions is 50.5 mM
(D) K+ will diffuse from solution A to solution B until a membrane
potential
develops with solution A negative with respect to solution B
(E) K+ will diffuse from solution A to solution B until a membrane
potential
develops with solution A positive with respect to solution B . Answer: 3.
The answer is D [IV B]. Because the membrane is permeable only to K+
ions, K+ will diffuse down its concentration gradient from solution A to
solution
B, leaving some Cl− ions behind in solution A. A diffusion potential will
be
created, with solution A negative with respect to solution B. Generation
of a
diffusion potential involves movement of only a few ions and, therefore,
does
not cause a change in the concentration of the bulk solutions.
◉4. The correct temporal sequence for events at the neuromuscular
junction is
, (A) action potential in the motor nerve; depolarization of the muscle end
plate;
uptake of Ca2+ into the presynaptic nerve terminal
(B) uptake of Ca2+ into the presynaptic terminal; release of
acetylcholine (ACh);
depolarization of the muscle end plate
(C) release of ACh; action potential in the motor nerve; action potential
in the
muscle
(D) uptake of Ca2+ into the motor end plate; action potential in the
motor end
plate; action potential in the muscle
(E) release of ACh; action potential in the muscle end plate; action
potential in
the muscle . Answer: 4. The answer is B [V B 1-6]. Acetylcholine (ACh)
is stored in vesicles and is
released when an action potential in the motor nerve opens Ca2+
channels in the presynaptic terminal. ACh diffuses across the synaptic
cleft and opens Na+ and K+ channels in the muscle end plate,
depolarizing it (but not producing an action
ACTUAL EXAM QUESTIONS WITH DETAILED
VERIFIED SOLUTIONS
◉2. During the upstroke of the nerve action potential
(A) there is net outward current and the cell interior becomes more
negative
(B) there is net outward current and the cell interior becomes less
negative
(C) there is net inward current and the cell interior becomes more
negative
(D) there is net inward current and the cell interior becomes less
negative . Answer: 2. The answer is D [IV E 1 a, b, 2 b]. During the
upstroke of the action
,potential, the cell depolarizes or becomes less negative. The
depolarization is caused by inward current, which is, by definition, the
movement of positive
charge into the cell. In nerve and in most types of muscle, this inward
current is carried by Na+
◉3. Solutions A and B are separated by a semipermeable membrane that
is
permeable to K+ but not to Cl−. Solution A is 100 mM KCl, and solution
B
is 1 mM KCl. Which of the following statements about solution A and
solution B is true?
(A) K+ ions will diffuse from solution A to solution B until the [K+] of
both
solutions is 50.5 mM
(B) K+ ions will diffuse from solution B to solution A until the [K+] of
both
solutions is 50.5 mM
(C) KCl will diffuse from solution A to solution B until the [KCl] of
both
,solutions is 50.5 mM
(D) K+ will diffuse from solution A to solution B until a membrane
potential
develops with solution A negative with respect to solution B
(E) K+ will diffuse from solution A to solution B until a membrane
potential
develops with solution A positive with respect to solution B . Answer: 3.
The answer is D [IV B]. Because the membrane is permeable only to K+
ions, K+ will diffuse down its concentration gradient from solution A to
solution
B, leaving some Cl− ions behind in solution A. A diffusion potential will
be
created, with solution A negative with respect to solution B. Generation
of a
diffusion potential involves movement of only a few ions and, therefore,
does
not cause a change in the concentration of the bulk solutions.
◉4. The correct temporal sequence for events at the neuromuscular
junction is
, (A) action potential in the motor nerve; depolarization of the muscle end
plate;
uptake of Ca2+ into the presynaptic nerve terminal
(B) uptake of Ca2+ into the presynaptic terminal; release of
acetylcholine (ACh);
depolarization of the muscle end plate
(C) release of ACh; action potential in the motor nerve; action potential
in the
muscle
(D) uptake of Ca2+ into the motor end plate; action potential in the
motor end
plate; action potential in the muscle
(E) release of ACh; action potential in the muscle end plate; action
potential in
the muscle . Answer: 4. The answer is B [V B 1-6]. Acetylcholine (ACh)
is stored in vesicles and is
released when an action potential in the motor nerve opens Ca2+
channels in the presynaptic terminal. ACh diffuses across the synaptic
cleft and opens Na+ and K+ channels in the muscle end plate,
depolarizing it (but not producing an action
