HBY 531 MEDICAL PHYSIOLOGY

Lecture Exam 1

2004

Section 1: Answer the following using:

A = increase

B = not change

C = decrease

1. If NaCl is added to the normal solution bathing a cell, cell volume will _____C__________.

2. If a neurotransmitter causes a reduction in cellular Na/K ATPase activity, steady state [Ca⁺²]_i will ______A_________.

3. Using the single channel patch clamp technique, it is seen that increasing [Ca⁺²] at the intracellular face of a K⁺-channel protein causes the fraction of time spent in the open state to increase. In the cell that was patch clamped, a rise in intracellular [Ca⁺²] would _______A_________ the membrane K⁺-conductance due to this channel.

4. Assume E_Cl = -70 mV. If a cell’s resting voltage is caused to abruptly change from -70 mV to -80 mV, over the next few minutes [Cl^-]_i will ________C_______.

5. A nerve axon is isolated and its action potential recorded. The voltage dependent sodium conductance is partially blocked with TTX. Assuming another action potential can be generated, the presence of TTX will cause action potential duration to ______A_________.

6. When a nerve cell membrane is slowly depolarized from -70 mV to -20 mV, the Na⁺-channel inactivation gate open probability, h, will _______C________.

7. An unmylinated axon is exposed to a hydrophobic chemical that inserts into its membrane and causes the membrane capacitance to increase from 1 :F/cm² to 2 :F/cm². Action potential propagation velocity will _______C_______.

8. Curare blocks ACh-Rs and as a consequences the amplitude of MEPPs will _______C________.

9. At a synapse in the CNS, an increase in presynaptic action potential frequency causes an increase in outward current in the postsynaptic cell. As a result, postsynaptic action potential frequency will ________C_______.

10. During contractile activity of skeletal muscle cell, creatine levels will ______A_________.

11. In skeletal muscle, an increase in external Ca²⁺-concentration will cause twitch amplitude to _______B________.

Section 2: For each of the following, choose the single best response.

12. A solution is made containing (in mM): NaCl =100; CaCl₂ =50; sucrose 50. Assuming osmotic coefficients are unity, the osmolarity of this solution is

A. 200 mOsm

B. 250 mOsm

C. 300 mOsm

D. 400 mOsm

E. 500 mOsm

13. A cell, initially in equilibrium, contains concentrations of permeants s_i =150 mM and impermeants S_i =150 mM. This cell is transferred to a large bath containing S_o =300 mM and s_o = 0. The ratio of final volume to initial volume is

A. ½

B. 2

C. 3

D. 1/3

E. 1

14. Which of the following is true of a biomembrane?

A. The lipid phase is permeable to ions

B. The lipid phase is permeable to glucose

C. The lipid phase is impermeable to small hydrophobic solutes

D. The proteins mediate the transport of ions

E. All of the above

15. Primary (ATP driven) active transport is directly used to control the intracellular concentration of

A. sodium

B. potassium

C. hydrogen

D. calcium

E. All of the above.

16. Membrane capacitance

A. increases with voltage.

B. increases with charge.

C. depends primarily on membrane proteins.

D. depends primarily on membrane lipids.

E. mediates ion movement across the membrane.

17. The conductance of a biomembrane is due to

A. The lipid bilayer.

B. The dielectric constant of oil.

C. Integral membrane proteins.

D. The surface charge.

E. The membrane voltage.

Questions 18-19 refer to the figure below:

Intracellular Extracellular

[Na]_o = 144 mM

[K]_o = 4 mM

[Cl]_o = ?

[Ca]_o = 2 mM

g_K = g_Cl = 1.1 mS/cm²

g_Na = 0.025 mS/cm²

g_Ca = 0.01 :S/cm²

18. R_i =

A. -92.5 mV

B. -89 mV

C. -60 mV

D. -80 mV

E. -69.5 mV

19. [A]_i =

A. 147 mM.

B. 149 mM.

C. 151 mM.

D. 153 mM.

E. 155 mM

20. At the peak of a nerve action potential, the ratio g_Na/g_K = 15. If E_Na = +60 mV and E_K = -100 mV, what is the voltage at the action potential peak?

A. +60 mV.

B. +50 mV.

C. +40 mV.

D. +30 mV.

E. +20 mV.

21. Threshold for an action potential is

A. the current at which the voltage switches from negative to positive.

B. the current at which the voltage switches from positive to negative.

C. the voltage at which the current switches from inward to outward.

D. the voltage at which the current switches from outward to inward.

E. the voltage at which the current change is zero.

22. During the relative refractory period,

A. g_Na is elevated over rest.

B. threshold is more positive than at rest.

C. inward current exceeds outward current.

D. g_K is inactivated.

E. none of the above is true.

23. Which of the following is a role of action potentials?

A. Regulation of contraction.

B. Signal for exocytosis.

C. Transmission of information.

D. Signal for contraction.

E. All of the above.

24. Which of the following would increase action potential propagation velocity?

A. An increase in axon length.

B. An increase in membrane capacitance.

C. An increase in peak g_Na.

D. An increase in peak g_K.

E. An increase in resistivity of axoplasm.

25. Given the data below for length constant 8 and capacitance per unit length C_m, if all else is equal, which skeletal muscle fiber would have the most rapid action potential propagation velocity?

A. 8 = 2.0 mm, C_m = 10 nF/mm.

B. 8 = 1.5 mm, C_m = 10 nF/mm.

C. 8 = 2.0 mm, C_m = 15 nF/mm.

D. 8 = 1.5 mm, C_m = 15 nF/mm.

E. 8 = 2.0 mm, C_m = 20 nF/mm.

26. Myasthenia gravis has caused a person to lose a large fraction of their ACh receptors. The miniature end plate potentials (MEPPs) recorded in muscle cells removed from this person will be

A. longer in duration than normal.

B. more frequent than normal.

C. larger in amplitude than normal.

D. smaller in amplitude than normal.

E. the same as normal. .

27. A patient has taken an unknown drug, which has caused muscle stiffness. EMG reveals normal nerve action potential activity but unusually high muscle action potential activity. The drug could be

A. an inhibitor of the ACh-receptor.

B. an inhibitor of presynaptic calcium entry.

C. an inhibitor of ACh synthesis.

D. an inhibitor of ACh breakdown.

E. any of the above.

Questions 28-29 refer to the figure below:

The whole cell patch technique is used to record the post synaptic potential (R_PS) from the cell body of a neuron. When the axon is not stimulated, the following are determined

R_PS = -70 mV

E_Na = +60 mV g_Na = 0.2 mS/cm²

E_K = -90 mV g_K = 1.3 mS/cm²

E_Cl = -70 mV g_Cl = 0 mS/cm²

The following data were obtained by recording R_PS while rapidly stimulating the axon

28. The post synaptic receptor is an ion channel selective for

A. K⁺

B. Na⁺

C. Cl^-

D. cations

E. anions

29. The post synaptic conductance change is

A. 1.0 mS/cm²

B. 1.5 mS/cm²

C. 0.5 mS/cm²

D. 2.0 mS/cm²

E. 0.2 mS/cm²

30. A smooth muscle cell

A. does not require extracellular Ca to contract.

B. is not striated.

C. contracts once for each " motor neuron action potential.

D. is relatively large and contains many nuclei.

E. has a well developed transverse tubular system.

31. The center of a sarcomere appears dark because of

A. thin filaments

B. thick filaments

C. cross bridges

D. Hansens zone

E. Z-lines

32. In smooth muscle, which of the following does not directly require ATP?

A. Ca-uptake by the SR.

B. Crossbridge cycling.

C. The Na/K pump that establishes E_Na and E_K.

D. Myosin kinase activity.

E. Ca-entry during the action potential.

33. A skeletal muscle cell can generate maximum active isometric tension at a sarcomere length of 2.7 :M, where the H-zone is 0.1 :m, then active isometric tension falls linearly to zero as the sarcomeres are stretched from 2.7 :M to 3.9 :M. How long is each thick filament?

A. 0.6 :M

B. 0.9 :M

C. 1.2 :M

D. 1.3 :M

E. 1.5 :M

34. What is the major source of energy for muscle for someone exercising at 85% of VO₂ max?

A. Plasma glucose

B. Muscle glycogen

C. Muscle triglycerides

D. Plasma free fatty acids

E. Muscle creatine phosphate

35. A Jamaican fruit, ackee (Blinghia sapida), contains a mitochondrial poison when the fruit is unripe. Ingestion of the unripe fruit causes Jamaican vomiting sickness. Which of the following would accompany the ingestion of unripe ackee?

A. hypoglycemia

B. increased blood lactate

C. increased fat oxidation

D. increased NADH production

E. increased blood pH

36. Training can increase endurance. What is the most important aspect for improved endurance?

A. increased cardiac output

B. increased gas exchange in the lungs

C. increased capillary density in the muscle

D. increased mitochondrial content of muscle

E. increased Type II fibers

37. Which of the following epithelial structures is NOT in contact with interstitial fluid?

A. serosal membrane of intestinal epithelium

B. lateral intercellular spaces in gallbladder epithelium

C. secretory canaliculus of gastric parietal (oxyntic) cell

D. basolateral membrane of urinary bladder epithelium

E. peritubular membrane in renal proximal-tubule cell

38. The processes of active glucose absorption by the renal proximal tubule, active NaCl secretion by the small intestines, and aldosterone-dependent Na⁺ absorption all share which of the following characteristics?

A. All are mediated by tight epithelia possessing high paracellular resistance.

B. All are inhibited by the serosal application of furosemide, an inhibitor of the Na⁺-K⁺-2Cl^- (NKCC) transporter.

C. All are inhibited by the serosal application of ouabain (or other cardiac glycoside).

D. All involve the cycling of K⁺ through Ba⁺⁺-sensitive K⁺ channels located in the apical membrane.

E. None of the above are characteristics of all three epithelial transport processes.

39. An epithelium bathed with identical Ringer’s solutions on either side has an apical-membrane potential of -30 mV (measured with respect to the mucosal solution), and a basolateral-membrane potential of -70 mV (measured with respect to the serosal solution). Ionic equilibrium potentials are as follows: E_Na equals +50 mV, E_K equals -100 mV and E_Cl equals -45 mV. Given these values, which of the following statements is FALSE?

A. Apical-membrane Na⁺ channels would result in an inward Na⁺ current.

B. Apical-membrane Cl^- channels would produce an influx of Cl^- into the cells.

C. The transepithelial potential equals -40 mV (measured with respect to the serosal solution).

D. Basolateral K⁺ channels would result in an efflux of K⁺ through the channels.

E. If the tight junctions were cation selective, then there would be paracellular absorption (lumen to serosal side) of both Na⁺ and K⁺.

40. Which of the following would be expected to be beneficial in the treatment of diarrhea resulting from cholera-like bacterial toxins in the gut?

A. Oral administration of isotonic saline (150 mM NaCl).

B. Oral administration of a saline solution containing glucose.

C. Oral administration of a saline solution containing milk of magnesia (magnesium hydroxide).

D. Administration of a drug that stimulates intestinal motility, thereby hastening elimination of the bacteria.

E. Administration of theophylline, a drug that inhibits phosphodiesterase.