One of the components of the nervous system of low-energy organisms (such as flatworms) is the area where nerve cells of such organisms are relatively concentrated, which is relative to the brain and spinal cord of higher organisms.
The nerve cord of this kind of organism has a higher position in its nervous system. For example, the "brain" of the planarian is just a transit station, and the stimulation received by the receptor passes through the "brain" and is transmitted to the nerve cord, and then to all parts of the body
