The intestine is an important part of our body, yet there are many secrets we don’t know about it. For example, the intestine is the only organ in our body that is not controlled by the brain and can still “work” normally. Even in the case of “brain death”, as long as the respiratory and circulatory systems are maintained, the intestine can still function normally and carry out normal nutrient absorption and excretion. Because of its amazing “independence” from the brain, we call the intestine the “second brain” of the human body. Further, the reason why the intestine is called the “second brain” of the human body is that it has the function of subconscious “autonomic nerves”. The autonomic nerves in the human body can be divided into sympathetic nerves and parasympathetic nerves according to their functions: sympathetic nerves are the priority activity when people are tense and excited, while parasympathetic nerves are relatively active when people are relaxed, as shown in the diagram below. When sympathetic nerves are in priority (such as when feeling scared), the human body will experience: dilated pupils, increased heart rate, vasoconstriction of skin and internal organs, dilated coronary arteries, increased blood pressure, small bronchial diastole, reduced gastrointestinal motility, relaxed bladder wall muscles, reduced saliva secretion, sweat secretion from sweat glands, and contraction of the erector spinae. When the parasympathetic nerves are in a priority state, for example, people feel sleepy after eating lunch, this is because the parasympathetic nerves of the autonomic nervous system are in a priority state during the process of promoting digestion in the body. Parasympathetic excitement is manifested by such reactions as narrowed pupils, slowed heartbeat, lowered blood pressure, narrowed bronchioles, increased secretion of digestive glands, dilated genital blood vessels, and constricted bladder. Now let’s take a look at this peculiar phenomenon: when a person is brain dead, the intestine can still perform the functions of digestion, absorption, and even excretion, you must now understand that the intestine is super autonomous and not governed by the brain consciousness. So, in this sense, we can say without exaggeration – the intestine is the second brain of the human body!