Nervous System and Senses
Ctenophores have no brain or central nervous system, but instead have a nerve net (rather like a cobweb) that forms a ring round the mouth and is densest near structures such as the comb rows, pharynx, tentacles (if present) and the sensory complex furthest from the mouth.
The largest single sensory feature is the aboral organ (at the opposite end from the mouth). Its main component is a statocyst, a balance sensor consisting of a statolith, a solid particle supported on four bundles of cilia, called "balancers", that sense its orientation. The statocyst is protected by a transparent dome made of long, immobile cilia. A ctenophore does not automatically try to keep the statolith resting equally on all the balancers. Instead its response is determined by the animal's "mood", in other words the overall state of the nervous system. For example if a ctenophore with trailing tentacles captures prey, it will often put some comb rows into reverse, spinning the mouth towards the prey.
Read more about this topic: Ctenophores, Description, Common Features
Famous quotes containing the words nervous, system and/or senses:
“He was the finest of our happy men;
He had all joys, he never thought of death;
He fiddled sometimes with his mind, and then
Shook off the tremor like a nervous wren....”
—Allen Tate (1899–1979)
“Intimately concerned as we are with the system of Europe, it does not follow that we are therefore called upon to mix ourselves on every occasion, with a restless and meddling activity, in the concerns of the nations which surround us.”
—George Canning (1770–1827)
“The damned are in the abyss of Hell, as within a woeful city, where they suffer unspeakable torments, in all their senses and members, because as they have employed all their senses and their members in sinning, so shall they suffer in each of them the punishment due to sin.”
—St. Francis De Sales (1567–1622)