Assume a length of axon membrane of about 10 cm is excited by an action potentia

Question

Assume a length of axon membrane of about 10 cm is excited by an action potential (length excited = nerve speed x pulse duration = 50 m/s x 2.0 ms = 10 cm). In the resting state, the outer surface of the axon wall is charged positively with K^+ ions and the inner wall has an equal and opposite charge of negative organic ions, as shown in the figure. Model the axon as a parallel-plate, capacitor and take C = ?? A/d and Q = C?V to investigate the charge as follows: Use typical values for a cylindrical axon of cell wall thickness d = 1.9 x 10^-8 m, axon radius r = 15.0 m, and cell-wall dielectric constant ? = 2.3. (a) Calculate the positive charge on the outside of a 10 cm piece of axon when it is not conducting an electric pulse. [Hint: calculate the charge per unit area in terms of the number of square angstroms ( A 2) per electronic charge. An atom has a cross-section of about 1 A 2 (1 A = 10^-10 m)]. C How many K^+ ions are on the outside of the axon? K^+ ions (b) How much positive charge must flow through the cell membrane to reach the excited state of +30 mV from the resting state of -70 mV? C How many sodium ions (Na+) is this? Na^+ ions (c) If it takes 2.0 ms for the Na+ ions to enter the axon, what is the average current in the axon wall in this process? A (d) How much energy does it take to raise the potential of the inner axon wall to +30 mV, starting from the resting potential of - 70 mV? J

Explanation / Answer

hope this link helps. http://www.jca.umbc.edu/~george/html/courses/phys112/2004fall/homework/04fall_phys112_hk4.pdf See Chapt18, Problem-41 for the solution .ThanQ

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