Editing Sea cucumber (section)

===Nervous system===
Sea cucumbers have no true [[brain]]. A ring of neural tissue surrounds the oral cavity, and sends nerves to the tentacles and the [[pharynx]]. The animal is, however, quite capable of functioning and moving about if the nerve ring is surgically removed, demonstrating that it does not have a central role in nervous coordination. In addition, five major nerves run from the nerve ring down the length of the body beneath each of the ambulacral areas.<ref name=IZ/>

Most sea cucumbers have no distinct sensory organs, although there are various nerve endings scattered through the skin, giving the animal a sense of touch and a sensitivity to the presence of light. There are, however, a few exceptions: members of the Apodida order are known to possess [[statocyst]]s, while some species possess small eye-spots near the bases of their tentacles.<ref name=IZ/>