Many sea stars can regenerate body parts. If a detached portion of a sea star contains part of the central disc, that portion can grow into a brand new star. Regeneration usually takes up to one year to complete. Not a bad survival trait to have, if you ask me. A nerve ring encircles the mouth.
Radial nerves extend into each arm and coordinate the functions of the tube feet.
A nerve net in the body wall coordinates other parts of the sea star's brainless nervous system. Sea stars sense light with red eyespots on each arm. Sensory tentacles at the end of each arm sense chemicals and vibrations in the water. But these animals are more than decoration. They are living creatures precious to the ocean and freshwater ecosystems.