#Id: 5457
                                                        #Unit 7. System Physiology – Animal
                                                        The number of Na + channels per square micrometer of membrane in myelinated mammalian neurons has been estimated: 
50–75 in the cell body, 350–500 in initial segment, less than 25 on the surface of the myelin, 2000–12,000 at the nodes of Ranvier & 20–75 at the axon terminals