The Nervous System: Membrane Potential

Topics: Neuron, Action potential, Nervous system Pages: 3 (267 words) Published: October 28, 2013
The Nervous System: Membrane Potential
1.

Record the intracellular and extracellular concentrations of the following ions (mM/L):

Intracellular

Extracellular

Sodium (Na+)
Potassium (K+)
Chloride (Cl–)

2.

Excitable cells, like neurons, are more permeable to ___________ than to ___________.

3.

How would the following alterations affect the membrane permeability to K+? Use arrows to indicate the change in permeability.
a. An increase in the number of passive K+ channels ___________ b. Opening of voltage-gated K+ channels ___________
c. Closing of voltage-gated K+ channels ___________

4.

a. What acts as a chemical force that pushes K+ out of the cell? ___________ 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 gradients in question 4 promote or oppose the movement of Cl– into the cell?
a.

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 compensates for the movement (leakage) of Na+ and K+ ions? ______________

10.

What will happen to the resting membrane potential of an excitable cell if: (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+ ___________

c.

↑ extracellular fluid concentration of Na+ ___________

d.

↓ number of passive Na+ channels ___________

e.

open voltage-gated K+ channels ___________

f.

open voltage-gated Na+ channels ___________...
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