So this neurotransmitter in this type of pathway is known as the first messenger or the primary messenger molecule. Now, also notice that this neurotransmitter doesn't actually go inside the cell of the muscle cell. Instead, it stays on the outside. It attaches onto the receptor of the protein membrane found on the extracellular side of that membrane. And in most cases, this is what takes place. In most cases, our first messenger doesn't actually go into our cell and create that response.