Conduction velocity in nonmyelinated axons

The conduction velocity (θ), the speed with which the nerve impulses are propagated, is fairly slow in nonmyelinated axons. It varies ranges between 0.5 and 2 ms^-1 depending on the diameter of the axon. The Small axons offer a very high resistance to the flow of currents through their cores than larger ones, merely as thin wires have a higher electrical resistance than thick ones. Therefore, local circuit currents in the axoplasm of small axons spread less well than in larger axons and this is the reason for the slower speed. Very roughly the relationship is shown as:

                 θ= ka^1/2

here a is the axon diameter and k is a constant that depends on the internal resistance of the axon and its membrane capacitance.