Answer:
The human cell system has a pretty advanced and effective way of communication. This communication between cells, whether it be of a single system, or between systems, is carried out by chemical reactions and gradients, and also through the intercession of molecules known as neurotransmitters. This is the case of the nervous system and its means of communication.
When we talk about neurotransmitters (the messengers) and neuroreceptors (the gatekeepers that receive the message and produce a reaction), we are literally talking about communication in the nervous system.
There are two types of neuroreceptors for trasmitters: the ionotropic (ligand-gated ion channels) and the metabotropic (second-messenger gated receptors, or G-protein coupled receptors). While the first type depends entirely on the availability of a ligand that binds to the receptor to open up the influx of ions from outside and inside of the cell to create a gradient that will ensure a cell response, the second does not open any ion channels and literaly what it does is receive the message from a neurotransmitter, and through the G-protein bound to the receptor, once it gets the necessary message, detaches and carries out the information to the cell. This is broadly how neurotransmittion can be carried out in the nervous system.
