My group and I researched how cells “communicate” in the brain neurons to create long-term memory. What we found is that, depending on how strong of a shock is sent, a certain amount of ligands, called glutamates, is released due to the shock. The glutamates will insert itself into a receptor, which in turn allows sodium (Na+) to enter the now open receptor. In the event of a strong shock, more sodium flows into the receptor. This positively charged sodium causes the positively charged magnesium (Mg+) to repel away from the other receptor which allows calcium (Ca+2) to enter. This strong shock is how long-term memory works in cells.
The video: https://drive.google.com/file/d/0B5Sihv4gNfm_ME9fZmlkdVRteWM/view