3. A myelinated nerve fiber has a 4.0-m-diameter cylindrical axon covered by a 1.0-m-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 m The dielectric constant of myelin is assumed to be 5.0, the same as that of the cell membrane

a) What are the capacitance in pF and the resistance in M 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 s of this RC circuit