Compare the intracellular and extracellularconcentrations for Na and K of a %u201Cgeneral%u201D mammalian cellto that in a squid which lives in the salty ocean. What are thevalues for Na and K out and in? (You can find values by going togoogle and typing in %u201Csquid axon ion concentrations%u201D orgoing to http://faculty.weber.edu/nokazaki/Comparative%20Animal%20Physiology/Tests/Chp%2011%20Essay%20questions.htm). Why are they different? Why is the voltage ofthe squid neuron so very similar to that of a %u201Cgeneral%u201Dmammalian cell (hint: is it the absolute concentrations of ionsthat are important or their ratios across the plasma membrane)?
You will be plotting the flowof ions -
which is an electrical current. When you make yourplots, the y axis
will be the amount of current flow. Make it sothat inward current
(that is, net flow of ions into the cell) isdownward (below zero), and
outward current (that is, the flow of ions out ofa cell) is positive.
Then, Use the Goldman equation and the Goldmanequation simulator to answer the following questions. Whenanswering "Why" questions, do so in one-two sentences.
Start with the default conditions in thesimulator.
PK = 100 Ko = 10mM Ki = 100
PNa =1 Nao =100 Nai = 1
PCl =10 Clo= 100 Cli = 10
What is the voltage of a cell that has thesevalues? Why
If the relative potassium permeability waschanged to 1, what would be the voltage of the cell? Why?
Change the permeability of K back to 100. Ifthe permeability to chloride is changed from 10 to 100, will therebe a voltage change? Why?
Change the permeability of chloride back to10. Now, change the extracellular concentration of potassium to 90mM. What is the voltage of the cell? Why?
Now change the extracellular concentration ofpotassium to 200. What is the voltage of the cell? Why? Now changethe permeability to potassium to 9999. Is there a further largechange in the voltage of the cell? Why?