MCAT physiology: Nernst and Goldman
The Resting Membrane
A patient's potassium doubles. A four-minute film that builds the resting potential from nothing, ion by ion, and shows why the membrane moves nine millivolts, not eighteen, and why that is enough to stop a heart.
This browser has 3D graphics turned off, so the set cannot be drawn. The math and the narration still play.
The problem
A neuron rests at -70 mV with [K+] = 4 mM outside and 140 mM inside, [Na+] = 145 mM outside and 15 mM inside. In a patient with hyperkalemia the extracellular potassium doubles to 8 mM. What happens to the resting membrane potential?
It depolarizes by about 9 mV, to about -61 mV (not the 18 mV Nernst alone would predict)
