In eukaryotes possibly the most rapid and complex signaling is mediated through nerve impulses.  The Nerve  cells  (neurons)  consist  of  a cell  body  with  numerous projections  of  the  plasma  membrane,  called as  dendrites.  These  interact with  other  cells  and  receive  information   from  them  in  the  form  of  nerve impulses. Cell body then assimilates the information derived from a number of dendritric contacts and passes on the information as another nerve impulse down the huge axon.  The axon ends at the synapse  where  it makes contact with the post-synaptic  (target) cell. The axon is covered  in places by a membranous  myelin  sheath,  made  up commonly  of the lipid sphingomyelin, that acts as an electrical insulator and enabling the nerve impulses to be trnasferred  over  long  distances  sometimes  more  than  1 m in larger  animals.

             figure:   Schematic diagram of a typical nerve cell.