Answer Happy

Data Analysis 1. Calculate the mean + the standard deviation (SD) for the membrane potentials in each saline. Exclude any values that are more than 2 standard deviations from the mean. 2. Provide a table showing all membrane potentials from which you calculated the means for different values of [Kl. 3. Plot the relationship between extracellular potassium concentration ([Kl.), and observed resting potential (Em) using semi-log graph paper. (Kl, is plotted on the abscissa (log scale) and (Em), in millivolts, is on the ordinate (arithmetic scale). How closely does your plot follow the Nernst relationship for K+lo (see Fig. 2)? 4. What is the slope of the line? Hint: Fit the line ONLY using points at [K], higher than 20 mM. What is the significance of this slope? 5. Can you estimate the internal concentration of potassium ([K+1) from this data? How? Compare your result those shown in Table 1 of (Djamgoz, 1987). 6. Can you estimate the permeability constant (PNa) from this data? How? 7. Be sure to read the publication by Hodgkin and Horowicz (1959) (Ref. 2), particularly the Discussion and Summary sections, which are useful for ideas about how to present and interpret your data.

2 Choline/5 mi 5 mM K 18 mMK 32 mMK 46 mMK 53 mMK 4 5 0 -69 -85 -69 -72 -70 7 -75 -64 -78 -68 -65 -69 -69.8 -61 -60 -56 -61 -58 -59 -59.2 -57 -47 -51 -48 -45 -44 -48.7 -42 -33 -40 -39 -41 -38 -38.8 -42 -24 -45 -39 -33 -34 -36.2 10 Average -69 -72.3 11 12