Nerve Net

A nerve net is a type of simple nervous system that is found in members of the cnidaria, ctenophora, and echinodermata phyla. Nerve nets consist of interconnected neurons lacking a brain or any form of cephalization. While organisms with bilateral body symmetry are normally associated with a central nervous system, organisms with radial body symmetry are associated with nerve nets.

The nerve net is the simplest form of a nervous system found in multicellular organisms. Unlike central nervous systems where neurons are typically grouped together, neurons found in nerve nets are found spread apart. This nervous system allows cnidarians to respond to physical contact. They may then detect food and other chemicals in a rudimentary way. Although the nerve net allows the animal to respond to its environment, it has trouble alerting the animal from where the stimulus is coming. For this reason, simple animals with nerve nets, such as hydra, will typically respond in the same way to contact with an object, regardless of where the contact occurs.

The anatomy and positioning of nerve nets can vary from organism to organism. Hydra, which are cnidarians, have a nerve net throughout their body. On the other hand, sea stars, which are echinoderms, have a nerve net in each arm, connected by a central radial nerve ring at the center. This is better suited to controlling more complex movements than a diffuse nerve net.