One of the reasons the human body is so mysterious is because it is a highly coupled system. A coupled system responds as a whole anytime a single subsystem is changed. Examples of this phenomenon include how psychological stress can lead to problems in other systems of the body such as the digestive system. In physics this often corresponds to how atoms rotate or vibrate together when part of a single molecule. Systems biology has arisen in order to clarify this phenomenon in living organisms. One important case is how multiple feedback loops operate in the brain. For example, serotonin’s presence can shift concentration of other neurotransmitters such as dopamine, enhancing mood and well-being. Conversely, low dopamine can decrease serotonin leading to a prolonged depression. This is a gross oversimplification; in reality the coupling arrangement of the mind is incredibly sophisticated. There are several isoforms of both presynaptic and postsynaptic neurotransmitter transporters. A temporarily pleasant sensation brought on by a dopamine agonist like cocaine can consequently lead to violent and antisocial behavior as the body compensates for its colossal neurotransmitter imbalance. This suggests the true reason for the intricately coupled nature of the body; a highly coupled system is effective at maintaining homeostasis. Anytime one subsystem goes erratic, the other subsystems can compensate for the imbalance. What in lay terms is called being high is more accurately a temporary imbalance of various neurotransmitters caused by a novel compound modifying the homeostatic predisposition of the body. Proteins are ideal for this role as the molecular switches of emotion due to their similarity yet profound difference.
Unfortunately the highly coupled nature of the body is why there are no ethically sound ways to conduct truly scientific experiments on humans. During the lengthy development time of a mature human being too many variables are uncontrollable from a scientific perspective. It would seem there are almost an infinite number of differences between any two human beings. Of course we superficially look similar, speak common languages, share socioeconomic backgrounds, and bear similar religious practices, but in a biomolecular sense the sum of every person’s life experiences is different. In a grander sense, the human body is a coupled system which is a part of the grander system which is Earth, and more indirectly, the universe
