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, nervous, system and/or senses:
“A car can massage organs which no masseur can reach. It is the one remedy for the disorders of the great sympathetic nervous system.”
—Jean Cocteau (1889–1963)
“The knocking out of a pipe can be made almost as important as the smoking of it, especially if there are nervous people in the room. A good, smart knock of a pipe against a tin wastebasket and you will have a neurasthenic out of his chair and into the window sash in no time.”
—Robert Benchley (1889–1945)
“It is not easy to construct by mere scientific synthesis a foolproof system which will lead our children in a desired direction and avoid an undesirable one. Obviously, good can come only from a continuing interplay between that which we, as students, are gradually learning and that which we believe in, as people.”
—Erik H. Erikson (20th century)
“Let me obtain forgiveness of thee, Samson,
Afford me place to shew what recompence
Towards thee I intend for what I have misdone,
Misguided; only what remains past cure
Bear not too sensibly, nor still insist
To afflict thy self in vain: though sight be lost,
Life yet hath many solaces, enjoy’d
Where other senses want not their delights
At home in leisure and domestic ease,”
—John Milton (1608–1674)