Practice question

Diffuse conduction system termed nerve net characterizes primitive nervous organization in Cnidaria and partially Ctenophora consisting interconnected neurons forming two-dimensional plexus in ectoderm and endoderm without brain ganglia conducting impulses slowly. Enables coordinated retraction tentacle movement feeding responses via radial spread. Epitheliomuscular cells innervated contract. Nerve rings exist around bell margin in medusae associated with rhopalia containing statocysts and ocelli. Such net represents early neural evolution stage before cephalization bilateral symmetry and centralization seen in bilaterians with complex brains and rapid directional conduction needed for active locomotion and sensory integration processes and coordinated behaviors essential.