It turns out that in addition to the brain on the top of our head, there is another organ hidden in our body that can control various emotional changes in the brain, which is the "gut".
The number of nerve cells in the intestine is second only to the brain. Generally speaking, the key to controlling intestinal nerves lies in the thousands of bacteria in the intestine.
If the brain is an "iPhone" that can handle all kinds of things, the intestines are the "Apple Watch" that connects to the iPhone and helps process peripheral information.
Different microorganisms (Gut Microbiome) in the intestines may stimulate other nerves, and the nerves will prompt the body to secrete different substances to stimulate the body.
For example, when we are nervous, the brain may release hormones to the intestines, speeding up their secretion and peristalsis, which may cause diarrhea. No wonder I always want to go to the toilet before every exam.
However, different microorganisms in the intestines can also improve physiological metabolism and even secrete "happy probiotics" (Serotonin, Dopamine) to improve our mood and reduce depression, autism, and other neurological-related diseases caused by stress or tension.