Really interesting thought, Lula! Maybe, in the spells, our Merlinians use? I could imagine, that, of course, the element fire is represented by the Merlin Circel and the Fire balls and, of course, as you mentioned, the electro-magnetical energy of the nervous system, the element water in the spell, Balthazar use, when he first rescues the 20 year old Dave, by throwing water into Horvath`face, to prevent him from casting his spell at Dave, the element air could be represented by the "eagle", Balthazar brings to live, and the "biometric pressure spell", he uses, to  displace the atmosphere above the doll, to locate the grimhold, and the element earth could, maybe, represented by the magic device/spell, Balthazar uses, to hide from Horvath, before rescuing the empty grimhold, at Battery park, in the last scene! (Although, you can maybe, also call that a gate). And, of course, the Merlin Circel itself had the alchemistic and elemental symbols within it! Well, that is, what I would imagine, could be the merlinian elements in the movie!