Assume a length of axon membrane of about 0.10 m is excited by an action potential (length excited = nerve speed x pulse duration50.0 m/s x 0.0020 s =0.10 m). In the%Dresting state, the outer surface of the axon wall is charged positively with Kt ions and the inner wall has an equal and opposite charge of negative organic ions, as shown in thefigure below. Model the axon as a parallel-plate capacitor and take C = KƐ A/d and Q = CAV to investigate the charge as follows. Use typical values for a cylindrical axon of cell-8wall thickness d = 1.5 x 10 m, axon radius r =2.0 x 10- um, and cell-wall dielectric constant K =2.9.External fluid+PositivechargelayerAxon wall membranedNegativechargelayerInternal fluidAxon radius = r(a) Calculate the positive charge on the outside of a 0.10-m piece of axon when it is not conducting an electric pulse. (Assume an initial potential difference of7.0 x 10-2 v.)1.035E-9Your response differs from the correct answer by more than 10%. Double check your calculations. C How many K* ions are on the outside of the axon assuming an initial potential difference of 7.0 x 10-2 v?Kt ionsIs this a large charge per unit area? Hint: Calculate the charge per unit area in terms of electronic charge e per angstrom squared (Å2). An atom has a cross section ofabout 1 Å2 (1 Å = 10¬10 m). (Compare to normal atomic spacing of one atom every few Å.)%3DYesNo(b) How much positive charge must flow through the cell membrane to reach the excited state of +3.0 x 10¬2 v from the resting state of -7.0 x 10-2 v?How many sodium ions (Na*) is this?Nat ions+(c) If it takes 2.0 ms for the Nat ions to enter the axon, what is the average current in the axon wall in this process?µA-2(d) How much energy does it take to raise the potential of the inner axon wall to +3.0 x 10 V, starting from the resting potential of -7.0 x 10¬2 V? (Assume that noenergy is required to first raise the potential to 0 V from the resting potential of -7.0 x 10-2 v.)J

Question

Accepted Answer

Given:
K=2.9, d=1.5×10-8m , η=1.9×10-5μm