But there's a little bit more to this communication highway: the receptors. They are attached to the oily surface (membrane) of the cells and receive messages from the ligands. The job of the receptor is to receive the incoming update on "Body-Brain News".

There are literally tens of thousands of receptors on a single cell. Each receptor is designed in a very specific way to receive only certain types of ligands. For example, on one cell (cells have different combinations of different receptors) there may be 10 000 opium receptors. That means that any opium or opium-like carrying peptide will be able to transmit its message in these 10 000 receptors. Another 50 000 receptors may be designed to receive some other ligand. It's almost as if each ligand has a specific code and only certain receptors know how to crack it.

The Dance of the Receptor and Peptide
Once a receptor and peptide "get together", they wiggle, shimmy and ultimately bind together so that the message the peptide had been carrying is transferred to the receptor. The peptide, after giving the news, "flies" away to carry on spreading the word, or it may be recycled into our body.

The message received by the receptor changes the cell in a specific way. The message is like a set of instructions for the cell to perform specific physiological activities, and it sets off a cascade of events. For example, the cell might be instructed to manufacture specific proteins and release them into the bloodstream or to divide itself. These activities then set off a chain reaction. The cell, also, can continue the flow of communication by creating its own peptides bearing news or information for the brain, e.g. "Brain, we have a problem."

We used to think that each of the body's systems (e.g. immune, endocrine and nervous systems) worked independently. As a result of research into peptides and receptors, scientists now understand how peptides enable the different systems in the body to communicate with each other.

Peptides and their receptors integrate all the functions of the body so that all systems work together.

Active Feedback Loops
The binding process between peptides and receptors can result in the cell releasing a molecule into the bloodstream. This molecule is picked up by a peptide-producing cell and conveys a message telling this cell which peptides to continue producing, and which peptides to halt production on. This process of message transfer is called feedback loops. They are the mechanism of receiving and responding to information. The body's mechanism for maintaining health and happiness is the ability to have rapid feedback loops throughout the psychosomatic (body and mind) network.