Stress is thought to be among the most important stimuli discussed by the brain and the gut. When the brain senses a major problem (such as time pressure or anger), it naturally wants to solve it. To do so, it needs energy, which it borrows mainly from the gut. The gut is informed of the emergency situation via the sympathetic nerve fibers, and is instructed to obey the brain in this exceptional period. It is kind enough to save energy on digestion, producing less mucus and reducing the blood supply.
