Nervous System I: Membrane Potential - Self Test
NOTE: This quiz is designed to be completed using the InteractivePhysiology CD that you used in the Muscle Lab. However, you should be able to answer most of the questions without the CD by using your class notes and your textbook.
1. Record the intracellular and extracellular concentrations of the following ions (mM/L):
| Ion | Intracellular Conc. | Extracellular Conc. |
| Na+ | ||
| K+ | ||
| Cl- |
2. Excitable cells, like neurons, are more permeable to ___________ than to ___________.
3. How would the following alterations affect the membrane permeability to K
+? (Increase, decrease, unchanged)a. An increase in the number of passive K+ channels ___________
b. Opening of voltage-gated K
+ channels ___________c. Closing of voltage-gated K
+ channels ___________b. What force tends to pull K
+ back into the cell? _________________________5. When the two forces listed above are equal and opposite in a cell permeable only to K+, this is called the _____________________ potential for K+ which is ___________ mV.
6. In an excitable cell, also permeable to Na+ and Cl-, the gradients mentioned
in question 4 would both tend to move Na+ ___________ the cell.
7. Would the two gradients in question 4 promote or oppose the movement of Cl- into the cell?
a. (Gradient a) -
b. (Gradient b) -
8. Since the neuron is permeable to Na+ as well as K+, the resting membrane potential is not equal to the equilibrium potential for K+, instead it is ___________ mV.
9. What opposes the movement (leakage) of Na+
and K+
ions?
_________________________
10. For each of the following conditions, will the resting membrane potential of an excitable cell become more positive or more negative: (Write pos or neg to indicate which way the membrane potential would change.)
a. extracellular fluid concentration of K
b. extracellular fluid concentration of K
+ increases ___________c. extracellular fluid concentration of Na
+ increases ___________d. open voltage-gated Na
+ channels increases ___________