Editing Crinoid (section)

===Nervous system===
The crinoid nervous system is divided into three parts, with numerous connections between them. The oral or uppermost portion is the only one [[homology (biology)|homologous]] with the nervous systems of other echinoderms. It consists of a central nerve ring surrounding the mouth, and radial nerves branching into the arms and is sensory in function. Below this lies an intermediate nerve ring, giving off radial nerves supplying the arms and pinnules. These nerves are motor in nature, and control the musculature of the tube feet. The third portion of the nervous system lies aborally, and is responsible for the flexing and movement actions of the arms, pinnules and cirri. This is centred on a mass of neural tissue near the base of the calyx, and provides a single nerve to each arm and a number of nerves to the stalk.<ref name=Ruppert/>