Answer
Nernst Equation:
$-RT/nF *(ln (c_{o} / c_{i}))$
Work Step by Step
Membrane potential considering only K+ ions:
58*log(9/344)
=58*log(0.026)
=58*-1.585
=-91.93mV
=-92mV
This is closer to the resting membrane potential.
Membrane potential considering only Na+ ions:
58*log(65/430)
=58*6.615
=58*0.82
=47.56 mV
=48 mV
This value is closer to the action potential.
This occurs because there are numerous leak K+ channels that allow K+ to leak untill the potential gradient cannot oppose their movement. Thus, this value is closer to the resting potential, and the Na+ channels only open when they are stimulated to be; that is, when the influx of Na+ reverses the potential of the membrane and therefore causes the neighboring Na+ channels to open. This stimulates the action potential.
