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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