2. From lecture, we've seen that myelin sheaths in nerve cells can be modelled using RC circuits with switch-activated batteries (Fig 2). Suppose an action potential is propagating from the left to the right, such that the left circuit's switch is closed, and the right is still open. The voltage of an action potential is VAP = IOOmV, the resistance of an axon is R, = 25M (2, and the capacitance of the membrane is C = 4pF. (a) What is the time constant of one of the circuits? (b) The switch activates/closes if the capacitor on the previous circuit has a voltage that is 90% of the of the action potential. Given that voltage over time on a charging capacitor is Vmp(t) = Vimt (ft/ROW, how long does it take for the switch to close? (* This was not explicitly covered in lecture, so don't worry if you haven't seen that equation before.) (c) If it takes an action potential 2ms to cross a nerve cell, and each \"circui \" corresponds to a myelin sheath, appr0ximately how many sheaths are on the nerve cell's axon? Figure 2