sea urchin nervous system?
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Here you go! Hope this helps.\n\nhttp://web.uvic.ca/~rburke/burkelab/neuraldevelopment.htm
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water vascular system helps the echinoderms in circulating the food & waste materials.....moreover it helps in their locomotion....
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Yes they are poisonous. As a diver I have been punctured and stung by sea urchins many times and have never experienced anything more than mild pain. Sea urchins have both spines which will puncture your skin, and some have Pedicellariea, which is an organ that delivers toxin, even after it breaks off from the sea urchin. Some species of sea urchins have been known to cause death. By the way, sea urchins are also good to eat. The edible part is the yellow roe inside their hollow body. This roe is called 'uni' on the sushi menu.
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The three answers above me only give you half of the answer.  There are muscarinic and choloinergic acetylcholine (Ache) receptors in the body.  \n\nI could give you what I know about Ach, but here is a complete list from wikipedia.com.  I even learned a few things about Ach from this information, and I have a PhD in neuroscience.\n\nAcetylcholine is released by:\n\nCNS neurons arising from 3 key areas:\n\nDorsolateral pons, which have broad targets through the brain, and are involved in REM sleep \n\nBasal Forebrain, the major source of cholinergic innervation throughout the cortex, implicated in the facilitation of learning \n\nmedial septum, which projects largely to the limbic system, and may induce rhythmic firing in the hippocampus critical to learning \n\nmany interneurons of the basal ganglia are also cholinergic \nsome PNS neurons, including \n\nmotor neurons (of the somatic nervous system), causing muscle contraction of striated muscle \n\nthe autonomic nervous system: \n\npre- and post-ganglionic parasympathetic neurons \n\npreganglionic sympathetic neurons (and also postganglionic pseudomotor neurons, i.e., the ones that control sweating) \n\nHope this is what you need.
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try this link and it should answer your question it is with diagram!\n\nhttp://en.wikipedia.org/wiki/Central_nervous_system
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Bipolar neurons \nPseudounipolar cells\nMultipolar neurons \nIs that it?
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There are no special organs regulating breathing in Sea Anemones, They breathe through their general body surface.\n\nAt each end of the mouth there is a permanent pore which opens into a siphonoglyph (ciliated groove) in the side of the gullet. A continuous current of water flows through here carrying oxygen and removing waste matter from the tissues.
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the motor neurons in the peripheral nervous system.
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Nervous system is the control center which consists of Brain, Spinal Cord and an enormous network of nerves that spread throughout your body. These nerves are responsible for the information flow between nervous system and other systems [ digestive, respiratory, circulatory etc etc ] in the entire body. Nervous system controls and coordinates the functioning of all other systems that exists in a body.
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Elasmobranchs (sharks, skates, and rays) indeed have an interesting sensory physiology enabling them to sense a variety of physical stimuli.  But fear is not one of them. That said, it is true though that fear may be associated with either the release of particular chemical compounds, but far more importantly and likey in regards to your question, with particular behavior.  And in that sharks are not very different from any other predator.\n\nThe sense of smell is indeed very well established in almost all elasmobranchs; if you ever take a look at a shark's brain note the extremely large bulbi olfactorii, the areas of the brain where smell is first analyzed.  The sentivity of shark noses for blood is often emphasized, but you must not imagine sharks to be "swimming noses."  Rather, they rely on different senses for different environmental conditions, prey, etc. The priority assigned to either one of the possible sensory modes is largely dependent on the life-style of the animal.  Given that there are over 400 different species, there are a few variations.\n\nLike many other aquatic animals (e.g., teleosts, but also amphibians) sharks rely on their lateral line organ for detecting objects in greater distances.  The lateral line organ is a tiny canal running along the side of the animal underneath the skin.  it is open to the environment through a set of pores, through which the shark can sense pressure differences in the water, as they are being produced for example by a fish in distress.  This can of course be misunderstood as "smelling fear," when in fact it is more like "sensing the panicked movements of a potential prey."\n\nThe electromagnetic sense of elasmobranchs is perhaps most amazing from a human point of view, since it is so very different from anything we have.  All elasmobranchs have Ampullae of Lorentzi, with which the animals can indeed sense bioelectric fields.  These organs are so sensitive that a dogfish can sense the bioelectric field induced by the beating heart of a flounder covered by sand.  Sharks also use this organ for a magnetic compass.  By swimming through the earth's magnetic field, a shark will induce an electric current that will either run from its back to its belly (when the animal swims in an eastern direction), or from its belly to its back (in western direction).  with its own electromagnetic sensores, the animal can sense the induced electric current and its direction and can thus orient itself along the magnetic field of the earth.  Again, very sexy and very helpful, but no detector of fear!\n\nNow, some sharks use their eyes when they hunt prey, and this may an important point in regards to your question.  Great white sharks (Carcharodon carcharias) often attack their prey (e.g., seals) from far below, orienting themselves visually in their attack and going for the tell-tale silhoutte of the pinniped.  Some sharks, like the lemon shark (Negaprion brevirostris), have an interesting eye, where the sensitivity of the retina changes from light of one particular wavelength during day time to one of a different wavelength during night time.  This Purkinje-shift allows the animals to see optimally during day and night.  Now, many animals (or humans) in distress show a particular behavior.  Sometimes, a flight response is what is initiated when faced with a predator.  This behavior can signal the shark that the fleeing animal (or human) is afraid and therefore not a danger but rather a potential prey.  Consequently, fear in humans that cause a flight response may cause sharks to respond accordingly.  This may also be misunderstood as "smelling fear."  This, by the way, is the same kind of behavior a cougar, dog, or bear will dislay.\n\nThat said, there is always the possibility that during fear a human may release certain chemical compounds that the shark can smell.  But I doubt that this is something really significant in a real-life encounter.\n\n
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echinoderms, chordates, hemichordates, protostomes, Ecdysozoa \nLophotrochozoa \nPlatyzoa
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Parasympathetic autonomic nervous system originates craniosacrally. Sympathetic nervous system orginates as a thoraco-lumbar outflow.
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Neuro-motor system, no way.  That would involve neurons and neurotransmitters.  None of these have been found in plants.\n\nHowever, there is definite physiologic responses that could be defined as behaviour in plants.  These responses and stimuli are much simpler than we can appreciate.
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Tasting, smelling, seeing, hearing, thinking, dreaming, breathing, heart beating, moving, running, sleeping, laughing, singing, remembering, feeling pain or pleasure, painting, writing...you couldn't do any of these things without your central nervous system! \n\nWhat is the nervous system? \nMade up of your brain, your spinal cord, and an enormous network of nerves that thread throughout your body, it's the control center for your entire body. Your brain uses information it receives from your nerves to coordinate all of your actions and reactions. Without it, you couldn't exist! \n\nWhat are nerves? \nThey're the thin threads of nerve cells, called neurons that run throughout your body. Bundled together, they carry messages back and forth just the way that telephone wires do. Sensory nerves send messages to the brain and generally connect to the brain through the spinal cord inside your backbone. Motor nerves carry messages back from the brain to all the muscles and glands in your body. \n\nSo how do they they pass along messages? \nThrough the marvels of chemistry and a kind of electricity! Neurons are thin. Some are very small, and some can be three feet long! All are shaped somewhat like flat stars which have, to varying degrees, been pulled at each end so that they have long fingers. The fingers of one neuron almost reach to the next neuron. \n\nWhen a neuron is stimulated -- by heat, cold, touch, sound vibrations or some other message -- it begins to actually generate a tiny electrical pulse. This electricity and chemical change travels the full length of the neuron. But when it gets to the end of finger-like points at the end of the neuron, it needs help getting across to the next extended finger. That's where chemicals come in. The electrical pulse in the cells triggers the release of chemicals that carry the pulse to the next cell. And so on and so on and so on. \n\nSource(s):\n\nsearch engine: ask.com\nkey words: The Nervous System\n(This is pretty broad in nature, is there a specific question related to an answer you need that I can help you with?\nohhhhhh...nurse?????
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Richard Dawkins has two wonderful chapters on cnidarians (jellyfish) and poriferans (sponges) in 'The Ancestor's Tale.'\n\nCnidarians have two body plans, the medusa (jellyfish) and the polyp (sea anemones and hydras).  Polyps often reproduce by budding and can make huge colonies of organisms.  The portuguese-man-of-war is actually a complex colony of medusa and polyp forms.  (BTW, he has a great discussion about how the stinger cell in jellyfish may be the most complex structure in any cell anywhere in the animal and plant kingdoms. Way cool!)\n\nPoriferans (sponges) are even simpler organisms.  Although they are ostensibly multicellular organisms, with several types of cells, these cells don't organize themselves into specialized tissues and organs. Sponges are able to reproduce both asexually and sexually.\n\nSo the evolutionary significance is that an individual is basically a colony.  As such they are right at the boundary between single-celled and multi-celled creatures.  They demonstrate how multi-celled organisms could arise as a colony of cooperating single-cells.
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http://en.wikipedia.org/wiki/Neurons
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The study of the nervous systems of organisms. Man included