membrane voltage question

the resting potential of a cell is −71.5 mV assuming conductance ratios of gK:gNa:gCl = 1: 0.02: 0.03 and equilibrium potentials of EK=-70mV, ENa=+50mV, ECl=-55mV.

 

a. Assume that the conductance ratios change to gK:gNa:gCl = 1:40:0, as might happen at the peak of the action potential. What is the membrane voltage under this condition?

 

b. Calculate the peak of a Calcium-based spike. Assume gK:gNa:gCl: gCa = 1:0:0:40. Is this more or less than the peak of the Sodium-based spike? Given that both conductances are the same, explain the discrepancy (1 sentence). Use ECa=+125mV. Goldman equation may be of help:

  

c. Draw the balance model for i) the peak of the sodium based action potential and ii) the peak of the calcium based action potential.