It's the same brain. All the nerve cells in your body are part of the overall brain of the system, and the "nerves" are axons and dendrites. The longest neuron in the body is the sciatic nerve. The cerebral cortex, which is the "thinking part of the brain" - is only a couple of millimeters thick at best, and this compares to what has now been discovered about the neurons of the enteric system.
Consideration of the micro biome and influence of metabolites which could shift the action of mind-gut nervous system should be of a prime concern, - as it would likely influence the baseline functioning of the organism.
For examples consider Ergot, chronic microbe infection and subtle "poisoning" such as may be the case in IBS, Arthritis, MS, ALS, Cancer, etc.
Whydening Gyre
May 19, 2017