Abstract
It has been thought that Autonomic nervous system (ANS) originated in lower vertebrate phyla and developed conspicuously in mammals. In accordance with this, the cerebrum which is small in lower vertebrates increased its volume in mammals. Therefore, it seems that the ANS and the cerebrum evolved in a similar time scale. In the previous annual meeting, we presented anovel hypothesis that the basic form of nervous system which plays similar roles to the ANS was molded in the earliest stage of metazoan evolution as early as phylum Cnidaria. According to the scenario, the ANS represents evolutionarily the oldest part of the nervous system whereas the cerebrum represents the newest part of it. A number of cychological diseases are more or less related to the malfunction of the ANS. From the scenario mentioned above, the troubles about the ANS is considered the result of the mismatch of the oldest and the newest part of the brain. If the mismatch continues to grow with the increase of cerebrum in volume, it is a possibility that in the near future the two systems fall apart failing to regulate organ functions properly. [Jpn J Physiol 55 Suppl:S189 (2005)]
