For the myelinated nerve the axon radius is 21 mu m the resi

For the myelinated nerve, the axon radius is 21 mu m, the resistivity of the membrane is rho_m = 1.0 times 10^7 ohm m, the axoplasm resistivity is r_a = 0.5 Ohm m. Assume that the myelin sheath thickness b is related to the axon race us a as a + b = 1.4a. What is the electro tonus spread decay length l (in cm) for this nerve? (Enter your answer to at least 2 decimal places.) Using D = 180a to quantify the distance D between nodes of Ranvier for this nerve, how many nodes of Ranvier are triggered along the nerve as a result of a certain node being stimulated? Use a potential difference of AV = 105 mV for the maximum potential change in the node that is Initially stimulated, and allow other nodes of Ranvier to be triggered if electro tonus spread at their site causes at least a change from -70 mV to -56 mV.

Solution

number of nodes= the distance D/ the total difference between potential

=180a/(70+26)-105

=180/126-105=180/21=8.5=>9

the answer is 9 nodes.