how systems from the endocrine system to the gut microbiome interact with the central nervous system and brain to generate and modify emotions

Our digestive system has a significant neural system of its own called the ‘enteric nervous system’ and given the (perhaps sensationalist) nickname ‘the second brain.’ There’s also the ‘intrinsic cardiac nervous system’ interfacing with our heart. There have been a lot of interesting results showing neuronal reactions to external stimuli. I don’t want to overstate things, as is so often the case with laypeople in the face of scientific mystery, but, at the very least, the brain isn’t entirely isolated when it comes to cognition.