3. A myelinated nerve fiber has a 4.0-um-diameter cylindrical axon covered by a 1.0-um-thick layer of myelin. No ions pass through the axon membrane, which is sealed by the myelin, but an action potential at a node causes an ion current to flow along the axis of the axon. The axon is filled with cytosol, whose resistivity was given in Chapter 24 as 0.50 0.m The dielectric constant of myelin is assumed to be 5.0, the same as that of the cell membrane (8 pts) Show your work. a) What are the capacitance in pF and the resistance in MQ of a 1.0-mm-long segment of a myelinated nerve fiber? Use the average radius of the myelin sheath for calculating capacitance. b) What is the time constant in us of this RC circuit