Nervous System of Echinoderms

Previous to studying the nervous system of echinoderms, you have to bear in mind the peculiar organization of these animals. Here as well, the nervous system is primitive, retaining the nature of the network pattern below the surface epithelium. The epithelium itself is strewn with sensory cells. Though, the network is, concentrated into ganglionated nerve cords. These retain the common radiate pattern of the group. You will see three systems here:

(i) The oral or the ectoneural system under the oral epidermis, made up of a ring around the oesophagus and a ganglionated strand extending from this ring along - each arm. Every cord is made up of tracts of fibers. This is the main system in most echinoderms.

(ii) The deeper Hyponeural system and

(iii) The aboral or apical system are much weak but organized on the same pattern as the, ectoneural system. So it is simple in structure and with close relationship with the epidermis, lacking ganglia or brain. Though, it has gone through certain amount of concentration, with circular and longitudinal cords. This marks the starting of a central nervous system.