Rick Mathias, 2000

1. Osmosis is

A The passive transmembrane diffusion of water.

B The active transmembrane transport of water.

C The flux of water due to a transmembrane hydrostatic pressure gradient.

D The passive transmembrane diffusion of solute.

E The active transmembrane transport of solute.

2. A cell is initially in equilibrium in a large bath containing 200 mOsm of permeant solute and 100 mOsm of impermeant solute. If the bath is changed to a final solution containing 150 mOsm of permeant solute and 150 mOsm of impermeant solute, what will be the ratio of final cell volume to initial cell volume.

A. 2/1

B. 2/3

C. 3/4

D. ½

E. 4/3

3. Intracellular K⁺ concentration is higher than extracellular owing to

A. K⁺ channels.

B. Na/K ATPase.

C. Osmosis.

D. Action potentials.

E. Endocytosis of K⁺ .

4. Secondary active transport

A. Establishes the electro-chemical gradient for Na that drives primary active transport.

B. Is used to phosphorylate ADP back to ATP in mitochondria.

C. Uses much less energy than primary active transport to transport a particular ion or nonelectrolyte.

D. Uses the energy stored in ATP to drive the transport of an ion or nonelectrolyte.

E. Uses the energy in the electro-chemical gradient for one ion to drive the transport of another ion or nonelectrolyte.

Questions 5-8 refer to the following diagram

5. What is intracellular K⁺?

A. 145 mM

B. 100 mM

C. 150 mM

D. 114 mM

E. 1 mM

6. If the membrane is permeable only to K⁺, what is the Na⁺ equilibrium potential, E_Na?

A. +240 mV

B. +120 mV

C. +60 mV

D. +0 mV

E. -60 mV

7. If the membrane is permeable only to Na⁺ and K⁺ and we can neglect any currents due to active transport, what is the resting voltage when the K⁺ conductance is three times the Na⁺ conductance, G_K = 3 G_Na?

A. +60 mV

B. 0 mV

C. -35 mV

D. -120 mV

E. -75 mV

8. If the membrane voltage is clamped at +60 mV, what is the driving force for movement of Na⁺ across the cell membrane?

A. +60 mV

B. 0 mV

C. -120 mV

D. 126 mV

E. 140 mV

9. During a nerve action potential, the opening of Na⁺ channels is responsible for

A. The absolute refractory period.

B. The relative refractory period.

C. Rapid hyperpolarization.

D. Rapid depolarization.

E. The hyperpolarizing after the potential.

10. During an action potential, the voltage dependent increase in Na⁺ current is due to

A. An increase in E_Na.

B. An increase in the number of Na⁺ channels.

C. A transient increase in the open channel probability of Na⁺ channels.

D. A transient increase in the open channel conductance of K⁺ channels.

E. An increase in Na/K pump activity.

11. Voltage dependent inactivation occurs when

A. Membrane capacitance inactivates.

B. Voltage dependent K⁺ channels inactivate.

C. Voltage dependent Na⁺ channels activate.

D. Na/K pumps inactivate.

E. Voltage dependent Na⁺ channels inactivate.

12. The relative refractory period is due to

A. An increase in the open probability of K⁺ channels and inactivation of Na⁺ channels.

B. Saltatory conduction.

C. The action potential upstroke.

D. The cardiac action potential plateau phase.

E. A reduction in threshold.

13. Multiple sclerosis is a disease in which myelin is destroyed by our immune system. Which of the following will not be a consequence of multiple sclerosis?

A. Propagation fails.

B. Safety factor decreases.

C. Threshold is reduced.

D. Weakness and paralysis.

E. Propagation velocity decreases.

14. Which of the following will increase the velocity of action potential propagation?

A. Myelination of the axon.

B. Increase in membrane capacitance.

C. Decrease in axon diameter.

D. Increase in the resistivity of the axoplasm.

E. Decrease in the length constant.

15. At the neuromuscular junction, botulinum poisoning blocks the entry of Ca²⁺ into the presynaptic nerve terminal. This will result in which of the following hcanges in end plate potential (EPP)?

A. An increase in EPP amplitude.

B. A decrease in EPP amplitude.

C. An increase in EPP frequency.

D. A decrease in EPP frequency.

E. A prolongation of the EPP.

16. At the neuromusclular junction, curare binds to the ACh receptor and prevents activation of the channel by ACh. This will result in which change to the miniature end plate potential (MEPP)?

A. An increase in MEPP frequency.

B. A decrease in MEPP amplitude.

C. A decrease in MEPP frequency.

D. An increase in MEPP amplitude.

E. A prolongation of the MEPP.

17. At a synapse in the CNS, temporal summation refers to

A. An excitatory post synaptic potential (PSP).

B. An inhibitory PSP.

C. A PSP resulting from a train of presynaptic action potentials in one nerve.

D. A PSP resulting from several presynaptic action potnetials from different nerves.

E. Several PSPs in different cell bodies.

18. A fast synapse means

A. The presynaptic action potential has a fast propagation velocity.

B. The presynaptic nerve is myelinated.

C. The post synaptic receptor is an ion channel.

D. The transmitter is released more rapidly than at a slow synapse.

E. The post synaptic receptor releases an intracellular second messenger.

19. A sacromere from a skeletal muscle fiber has the length-tension curve shown below. What is the length of the I band?

A. 0.5 mm

B. 1.0 mm

C. 1.5 mm

D. 2.5 mm

E. 3.0 mm

20. In smooth muscle, regulation of crossbridge cycling involves

A. A myosin kinase.

B. A myosin phosphatase.

C. Intracellular ATP.

D. Intracellular Ca²⁺

E. All of the above.

21. In skeletal muscle, which of the following directly involves the energy stored in ATP?

A. Ca²⁺ uptake into the SR.

B. Crossbridge cycling.

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

D. Phosphorylation of creatine to creatine phosphate.

E. All of the above.

22. Cardiac muscle contractility is more sensitive to extracellular calcium that is skeletal muscle because

A. The above premise is not correct.

B. Cardiac muscle cells are connected by gap junctions.

C. Cardiac muscle does not tetanize.

D. Its action potential has a calcium current.

E. Cardiac muscle contraction is more rapid than is skeletal muscle.