Problem: An isolated unexcitable cell has a resting membrane potential of -65 mV. A neuroscientist studying this cell injects it with an electrical current equal to 0.15 nA and observes that the membrane potential rises to -45 mV. The experimenter calculates the total membrane conductance of the cell from this data, and then adds a Na blocker to the medium, which is not 100% effective, so that GNa becomes only 5 times lower than it was before. Unexpectedly, both GK and GCl- are also affected by this Na blocker, becoming 30% higher and 40% lower, respectively, than before. The observed change in the membrane potential upon injection of the same current in the presence of the Na blocker is (ΔVm)Na blocked = 30 mV. Then, a very selective and effective K blocker was added to the medium (without removing the first blocker), eliminating the conductance for K ions completely. The observed change in the membrane potential upon injection of the same current in the presence of the Na and K blockers is (ΔVm)Na /K blocked = 45 mV. Find the values of the Na , K , and Cl- ion conductances before the blockers were added.