Q: What exactly are urban legends? A: Urban legends are popular stories alleged to be true and passed from individual to individual via oral or written (e.g. forwarded email) communication.: What exactly are urban legends? A: Urban legends are popular stories alleged to be true and passed from individual to individual via oral or written (e.g. forwarded email) communication.
When a person gets injured, their brains release chemicals called opioids into the space between neurons that acts to dull the pain signals. The effect is seen the most in the brain regions called the ventral striatum, amygdala, midline thalamus, and periaqueductal gray.
I started... Serotonin while not a brain chemical is released by repetitive motion. Repetitive motion such as suckling or chewing gum releases the chemical which is a blood chemical most of which resides in the gastrointestinal tract. It is no surprise that people who are in stressful situations resort to repetitive motion to deal with it.