Source Naturals Taurine provides a calming neurotransmitter. 

Taurine is a crystalline, free-form amino acid and supply's a soothing, inhibitory neurotransmitter and plays a major role in stabilizing the heartbeat and electrical activity of the nerves.

Taurine is also necessary for the proper functioning of the "sodium/potassium ATP-ase pump", which regulates the ion balance between the cells and the extracellular fluid that surrounds them.