Resting membrane potential [K+] changed

 

The figure on the left shows part of a normal neuron with the following labeled:

      Sodium ion (Na+) and potassium ion (K+) concentrations (measured in mM)

      Resting membrane potential (-70 mV)

      Na+ channels (black boxes) and K+ channels (gray boxes)

The resting membrane of a normal neuron has many more open K+ channels than open Na+ channels.

 

What happens to the resting membrane potential if the concentration of K+ outside of the cell is changed from 5 mg/L to 50 mg/L? This change to the K+ concentration outside the neuron is shown in the figure on the right. Note: The concentrations of Na+ are not changed.
In this new situation, the resting membrane potential will

a.         become more positive than -70 mV.

b.         become more negative than -70 mV.

c.         stay the same at -70 mV.

 

Explain your reasoning about what happens to the resting membrane potential if the concentration of K+ outside of the cell is changed from 5 mg/L to 50 mg/L and the concentrations of Na+ are not changed.

 

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This material is based upon work supported by the National Science Foundation (DUE grants: 1438739, 1323162, 1347740, 0736952 and 1022653). Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.