The Neuromuscular Junction

If such a nerve fiberwere to be directly joined to amuscle fiber of, say, 50μmin diameter, then as the propagating action potential reached the nerve–muscle junction, the local circuit current density set up in the muscle would be considerably reduced from that in the nerve. This reduction would occur because the nerve and muscle must have the same total current, a consequence of current conservation. However, since the muscle fiber/nerve fiber effective membrane area is at least the ratio of their respective radii, namely, (50/1.5) = 33.33, the ratio of their current densities must be in the reciprocal, that is, 0.03.