Review Test

Directions: Each of the numbered items or incomplete statements in this section is followed by answers or by completions of the statement. Select the ONE lettered answer or completion that is BEST in each case.

1. Which of the following characteristics is shared by simple and facilitated diffusion of glucose?

(A) Occurs down an electrochemical gradient

(B) Is saturable

(C) Requires metabolic energy

(D) Is inhibited by the presence of galactose

(E) Requires a Na+ gradient

2. During the upstroke of the 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

8. Solutions A and B are separated by a semipermeable membrane that is permeable to K+, but not to CI". Solution A is 100 mM KC1, and solution B is 1 mM KC1. 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) KC1 will diffuse from solution A to solution B until the [KC1] 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

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

5. Which characteristic or component is shared by skeletal muscle and smooth muscle?

(A) Thick and thin filaments arranged in sarcomeres

(B) Troponin

(C) Elevation of intracellular [Ca2+] for excitation-contraction coupling

(D) Spontaneous depolarization of the membrane potential

(E) High degree of electrical coupling between cells

6. Repeated stimulation of a skeletal muscle fiber causes tetanic contraction because the intracellular concentration of which solute increases

and

remains at high levels?

(A)

Na+

(B)

K+

(C)

CI

(D)

Mg2+

(E)

Ca2+

(F)

Troponin

(G)

Calmodulin

(H)

Adenosine triphosphate (ATP)

7. Solutions A and B are separated by a membrane that is permeable to Ca2+ and impermeable to CI". Solution A contains 10 mM CaCl2, and solution B contains 1 mM CaCl2. Assuming that 2.3 RT/F = 60 mV, Ca2+ will be at electrochemical equilibrium when

(G) the Ca2+ concentrations of the two solutions are equal

(H) the CI concentrations of the two solutions are equal

8. A person with myasthenia gravis notes increased muscle strength when he is treated with an acetylcholinesterase (AChE) inhibitor. The basis for his improvement is increased

(A) amount of acetylcholine (ACh) released from motor nerves

(B) levels of ACh at the muscle end plates

(C) number of ACh receptors on the muscle end plates

(D) amount of norepinephrine released from motor nerves

(E) synthesis of norepinephrine in motor nerves

9. In error, a patient is infused with large volumes of a solution that causes lysis of his red blood cells (RBCs). The solution was most likely

(A) isotonic NaCl

(B) isotonic mannitol

(C) hypertonic mannitol

(D) hypotonic urea

(E) hypertonic urea

10. During a nerve action potential, a stimulus is delivered as indicated by the arrow shown in the following figure. In response to the stimulus, a second action potential

Stimulus

Stimulus

(A) of smaller magnitude will occur

(B) of normal magnitude will occur

(C) of normal magnitude will occur, but will be delayed

(D) will occur, but will not have an overshoot

(E) will not occur

11. Solutions A and B are separated by a membrane that is permeable to urea. Solution A is 10 mM urea, and solution B is 5 mM urea. If the concentration of urea in solution A is doubled, the flux of urea across the membrane will

(A) double

(B) triple

(C) be unchanged

(D) decrease to one-half

(E) decrease to one-third

12. A muscle cell has an intracellular [Na+] of 14 mM and an extracellular [Na+ ] of 140 mM. Assuming that 2.3 RT/F = 60 mV, what would the membrane potential be if the muscle cell membrane were permeable only to Na+ ?

Questions 13-15

The diagram of a nerve action potential applies to Questions 13-15.

-»r^Na+ equilibrium potential

K+ equilibrium potential

Time (msec)

13. At which labeled point on the action potential is the K+ closest to electrochemical equilibrium?

14. What process is responsible for the change in membrane potential that occurs between point 1 and point 3?

(A) Movement of Na* into the cell

(B) Movement of Na+ out of the cell

(C) Movement of K+ into the cell

(D) Movement of K+ out of the cell

15. What process is responsible for the change in membrane potential that occurs between point 3 and point 4?

(A) Movement of Na+ into the cell

(B) Movement of Na+ out of the cell

(C) Movement of K+ into the cell

(D) Movement of K+ out of the cell

16. The rate of conduction of action potentials along a nerve will be increased by

(A) stimulating the Na+-K+ pump

(B) inhibiting the Na+-K+ pump

(C) decreasing the diameter of the nerve

(D) myelinating the nerve

(E) lengthening the nerve fiber

17. Solutions A and B are separated by a semipermeable membrane. Solution A contains 1 mM sucrose and 1 mM urea. Solution B contains 1 mM sucrose. The reflection coefficient for sucrose is one and the reflection coefficient for urea is zero. Which of the following statements about these solutions is correct?

Solution A has a higher effective osmotic pressure than solution B

Solution A has a lower effective osmotic pressure than solution B

Solutions A and B are isosmotic

Solution A is hyperosmotic with respect to solution B, and the solutions are isotonic

Solution A is hyposmotic with respect to solution B, and the solutions are isotonic

18. Degeneration of dopaminergic neurons has been implicated in

(A) schizophrenia

(B) Parkinson's disease

(C) myasthenia gravis

(D) curare poisoning

19. The permeability of a solute in a lipid bilayer will be increased by an increase in the

(A) molecular radius of the solute

(B) oil/water partition coefficient of the solute

(C) thickness of the bilayer

(D) concentration difference of the solute across the bilayer

20. A drug completely blocks Na+ channels in nerves. Which of the following effects on the action potential would it be expected to produce?

(A) Block the occurrence of action potentials

(B) Increase the rate of increase of the upstroke of the action potential

(C) Shorten the absolute refractory period

(D) Abolish the hyperpolarizing afterpotential

(E) Increase the Na+ equilibrium potential

21. At the muscle end plate, acetylcholine (ACh) causes the opening of

(A) Na+ channels and depolarization toward the Na+ equilibrium potential

(B) K+ channels and depolarization toward the K+ equilibrium potential

(C) Ca2+ channels and depolarization toward the Ca2+ equilibrium potential

(D) Na+ and K+ channels and depolarization to a value halfway between the Na+ and K+ equilibrium potentials

(E) Na+ and K+ channels and hyperpolarization to a value halfway between the Na+ and K+ equilibrium potentials

22. An inhibitory postsynaptic potential

(A) depolarizes the postsynaptic membrane by opening Na+ channels

(B) depolarizes the postsynaptic membrane by opening K+ channels

(C) hyperpolarizes the postsynaptic membrane by opening Ca2+ channels

(D) hyperpolarizes the postsynaptic membrane by opening CI channels

23. Which of the following would occur as a result of the inhibition of Na+,K+-ATPase?

(A) Decreased intracellular Na+ concentration

(B) Increased intracellular K+ concentration

(C) Increased intracellular Ca2+ concentration

(D) Increased Na+-glucose cotransport

(E) Increased Na+-Ca2+ exchange

24. Which of the following temporal sequences is correct for excitation-contraction coupling in skeletal muscle?

(A) Increased intracellular [Ca2+]; action potential in the muscle membrane; cross-bridge formation

(B) Action potential in the muscle membrane; depolarization of the T tubules; release of Ca2+ from the sarcoplasmic reticulum (SR)

(C) Action potential in the muscle membrane; splitting of adenosine triphosphate (ATP); binding of Ca2+ to troponin C

(D) Release of Ca2+ from the SR; depolarization of the T tubules; binding of Ca2+ to troponin C

25. Assuming complete dissociation of all solutes, which of the following solutions would be hyperosmotic to 1 mM NaCl?

26. Which of the following events occurs before depolarization of the T tubules in skeletal muscle in the mechanism of excitation-contraction coupling?

(A) Depolarization of the sarcolemmal membrane

(B) Opening of Ca2+ release channels on the sarcoplasmic reticulum (SR)

(C) Uptake of Ca2+ into the SR by Ca2+-adenosine triphosphatase (ATPase)

(D) Binding of Ca2+ to troponin C

(E) Binding of actin and myosin

27. Which of the following is an inhibitory neurotransmitter in the central nervous system (CNS)?

(A) Norepinephrine

(B) Glutamate

(C) Gamma-aminobutyric acid (GABA)

(D) Serotonin

(E) Histamine

28. Adenosine triphosphate (ATP) is used indirectly for which of the following processes?

(A) Accumulation of Ca2+ by the sarcoplasmic reticulum (SR)

(B) Transport of Na+ from intracellular to extracellular fluid

(C) Transport of K+ from extracellular to intracellular fluid

(D) Transport of H+ from parietal cells into the lumen of the stomach

(E) Absorption of glucose by intestinal epithelial cells

Directions: Each set of matching questions in this section consists of a list of four to twenty-six lettered options (some of which may be in figures) followed by several numbered items. For each numbered item, select the ONE lettered option that is most closely associated with it. To avoid spending too much time on matching sets with large numbers of options, it is generally advisable to begin each set by reading the list of options. Then, for each item in the set, try to generate the correct answer and locate it in the option list, rather than evaluating each option individually. Each lettered option may be selected once, more than once, or not at all.

Questions 29-32

(A) Simple diffusion

(B) Facilitated diffusion

(C) Primary active transport

(D) Cotransport

(E) Countertransport

Match each numbered description with the correct type of transport.

29. Transport of d- and l-glucose proceeds at the same rate down an electrochemical gradient

30. Transport of glucose from the intestinal lumen into a small intestinal cell is inhibited when the usual Na+ gradient across the membrane is abolished

31. Upstroke of the nerve action potential

32. Transport of K+ ions from extracellular fluid to intracellular fluid is inhibited by digitalis

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