Assume the length of an axon membrane of about 0.10 cm is excited by an action potential (length excited = nerve speed x

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Assume The Length Of An Axon Membrane Of About 0 10 Cm Is Excited By An Action Potential Length Excited Nerve Speed X 1 (219.04 KiB) Viewed 42 times

Assume the length of an axon membrane of about 0.10 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 below. Model the axon as a parallel-plate capacitor and take C = KE A/d and Q = CAV to investigate the charge as follows. Use typical values for a cylindrical axon of cell thickness d = 1.6 × 10-8 m, axon radius r = 1.9 x 10¹ μm, and cell-wall dielectric constant x = 2.4. Positive charge layer Negative { charge layer External fluid Axon wall membrane Internal fluid Axon radius = r + + (a) How much energy does it take to restore the inner wall of the axon to -7.0 x 10-² V from +3.0 x 10-² V? (Assume that no energy is required to first restore the potential to 0 V from the excited potential of +3.0 x 10-² V.) (b) Find the average current in the axon wall during this process. (Hint: The time required to return to the resting state is 3.0 ms.) μА