Sample Questions

Sample Math questions.

For problems requiring ion concentrations, use these values.

2. Using the values in the above table, estimate the membrane potential of this cell given that the conductances of sodium, potassium and chloride are 6, 39, and 5 nSiemens, respectively.

3. In the above example (question #2), the value for the conductance of potassium is 39 nS.  If the conductance to potassium were to increase, how would this affect the membrane potential?

a.  It would increase (more positive number)
b.  It would not change
c.  It would decrease (more negative number)

4. Assume that the resting membrane of a cell is determined primarily by the equilibrium potential of potassium.  If you insert an electrode into this cell and clamp the membrane voltage to +20 mV, would K⁺ be moving into or out of the cell through the potassium channels?

5. If you were conducting this experiment, what would be a typical membrane voltage that you would clamp the membrane to in order to get K+ to move in the opposite direction to the answer in the above question?

6. You isolate cells that have only K⁺ channels. You also have a drug that causes this channel to open. With a voltage clamp apparatus, you find, as expected, that in the presence of the drug the membrane potential is dependent on the concentration of extracellular K⁺ used in the experiment. At one concentration of K⁺ of 5 mM, you find that Vm is -80.5 mV. From this information, calculate the intracellular K⁺ concentration.

Sample Multiple choice questions

7. The operation of the sodium channel during the action potential can be modeled as a two gate channel, an activation (m gate) and an inactivation gate (h gate). Of the following 4 events that occur during the action potential, which event is occurring in a population of sodium channels in a segment of the membrane during the period of time known as the relative refractory period.

a. the activation gate is opening
b. the inactivation gate opening
c. the inactivation gate closing
d. the activation gate is closing

8. Arrange the following events associated with synaptic transmission in chronological order. Label the first event #1 and the last event #7.

___ release of neurotransmitter
___ increased conductance of Na⁺ through the Na⁺ channel in the postsynaptic membrane
___ increased conductance of Na⁺ through the Na⁺ channel in the presynaptic membrane
___ increased permeability of Ca²⁺ in the presynaptic membrane
___ binding of the neurotransmitter to its receptor

Sample short answer questions

9. Briefly explain why the resting membrane potential of most cells is susceptible to changes in plasma levels of potassium.

10. Myasthenia gravis is a disease in which there are fewer functional receptors for acetyl choline in the postsynaptic membrane of the neuromuscular junction. This disease is characterized by muscle weakness. Explain how a drug might function on the enzyme acetylcholine esterase to alleviate the symptoms of this disease.

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