In my Google days, I believe I read that serotonin was found mostly in the gut- where the SSRI/depression commericals would have you think that it was mainly found in the brain. Maybe this is a component to your intestine "food for thought". Hee hee THAT IS A JOKE PEOPLE!! LAUGH!! OK, maybe a dumb one!!
Zeke, you are not correct on the heart. Yes, the kidney is part of the issue but it is not that cut and dry to say heart problems are not the heart but the kidney. In some instances the kidney does not function appropriately and heart disease will ensue ie diabetes, kidney disease. However sometimes the heart IS the issue and over time the alteration in the heart's ability to function creates dysfunction in the organs that are required to maintain balance. Yes hormones are found in the gut and the process is complicated however GABA is a neurohormone and the cascades are not as simple as in the gut or in the brain. When you are dealing with engineering and math etc things can be measured exactly and the physics is an exact science. Physiology although based on many principles that are physics is far more complex and can not be broken down into the black and white components that you are trying to draw.
Kit