4) Recall that after the Na+ channels open the K+ channels open. Again to make the calculations relatively simple, solve the Goldman equation again with all resting conditions EXCEPT a 100 fold increase in potassium permeability. (2 points) [Hints, first, while I always stress the importance of units, in this case the simplified equation uses lumped constants (RT/F) and thus the units are factored in – so you can, this time, ignore the units. Second, remember that Cl- is a negative ion and thus in both the Nernst equation and Goldman equation you must remember to in and out concentrations are reversed relative to the cations]
To solve this equation, you will need to use the following concentrations inside (i) and outside (o) the cell and permeabilities (P) of sodium (Na+), potassium (K+) and chloride (Cl-) for the neuron: Ko = 5 (all) Ki = 150 Nao = 150 Nai = 15 Clo = 125 Cli = 9 PNa= 10-9, PK = 10-8 PCl = 10-9 (
All concentrations in mM and permeabilities are in units of cm/s but see “hints” below)
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