Exo is spitting big things out. endo is pulling big things in. diffusion is molecules moving from an area of high concentration to an area of low concentration until it is balanced
You didn't really provide any possible answers here. However, it's very easy to say that the responsible actors for impulse transmission across the synapses from one nervous cell to another nervous cell is what we call neurotransmitters. These are special molecules that can have different effects when binding onto the required receptor sites.