Of course, the neural connections between the brain and the body are not directly "crossed" together, otherwise "control confusion" will occur; Therefore, nerve cells are connected one by one, and there is only a small gap between them for some neurotransmitters to pass through.
Such a structure is the optimal structure; Because this can accurately control the corresponding body before the brain is injured; But once the brain is injured, through the action of various "neurotransmitters", especially "adrenaline", those nerves that are not controlled by the brain will break and grow, and finally reconnect with healthy brain nerves.
● At this time, you may also think: If it is parallel, isn't it good to grow into a cross after brain injury? However, in contrast, the recovery of "crossing" is still fast, after all, the distance is different; So since there is a better recovery method, the process of evolution will naturally choose it.
However, there are different recovery periods of nerve reconnection according to age; It is best to recover in childhood, but it is more difficult in adulthood.
● Medical practice cases: There are several cases in the world of people who have only "half a brain" but their lives have not been greatly affected (usually having brain surgery in childhood); There are also cases of adult brain injury gradually recovering; You can find the video of DISCOVERY's cranial nerves on the Internet.
● Brain injury, gradual recovery is the instinct of the brain (subconscious).
● Consciousness controls the brain, uses the brain to control the trunk, and consciousness is divided into two. This is schizophrenia.
Answer the landlord's supplementary question: Parallelism means that the nerve conduction processes do not cross and the transmission between signals is independent. Once damaged, the signals of the left and right brains have no chance to control the previously uncontrolled parts. If there is an intersection, the signal can be transmitted and controlled. For example, if the left brain is injured, the right brain can also send signals to the parts of the body that were originally controlled by the left brain.