Which Would Be Present In An Animal With A Nerve Net?
Learning Outcomes
- Differentiate betwixt the nervous systems of different animals
Nervous systems throughout the animal kingdom vary in structure and complexity, as illustrated by the multifariousness of animals shown in Effigy 1. Some organisms, like sea sponges, lack a true nervous system. Others, similar jellyfish, lack a truthful brain and instead have a arrangement of dissever but connected nerve cells (neurons) chosen a "nerve internet." Echinoderms such as ocean stars accept nerve cells that are bundled into fibers called nerves.
Flatworms of the phylum Platyhelminthes have both a central nervous system (CNS), made upwards of a pocket-size "brain" and two nervus cords, and a peripheral nervous system (PNS) containing a organization of nerves that extend throughout the body. The insect nervous organization is more than complex simply also fairly decentralized. It contains a encephalon, ventral nervus string, and ganglia (clusters of connected neurons). These ganglia can control movements and behaviors without input from the encephalon. Octopi may take the most complicated of invertebrate nervous systems—they take neurons that are organized in specialized lobes and eyes that are structurally similar to vertebrate species.
Figure i. Nervous systems vary in structure and complication. In (a) cnidarians, nerve cells form a decentralized nerve net. In (b) echinoderms, nervus cells are bundled into fibers called nerves. In animals exhibiting bilateral symmetry such as (c) planarians, neurons cluster into an anterior encephalon that processes information. In addition to a brain, (d) arthropods have clusters of nerve cell bodies, called peripheral ganglia, located along the ventral nervus string. Mollusks such equally squid and (e) octopi, which must chase to survive, have complex brains containing millions of neurons. In (f) vertebrates, the encephalon and spinal cord incorporate the key nervous system, while neurons extending into the balance of the trunk comprise the peripheral nervous system. (credit eastward: modification of work past Michael Vecchione, Clyde F.Due east. Roper, and Michael J. Sweeney, NOAA; credit f: modification of piece of work past NIH)
Compared to invertebrates, vertebrate nervous systems are more than circuitous, centralized, and specialized. While there is great diversity amongst different vertebrate nervous systems, they all share a basic construction: a CNS that contains a brain and spinal cord and a PNS made up of peripheral sensory and motor fretfulness. One interesting difference between the nervous systems of invertebrates and vertebrates is that the nervus cords of many invertebrates are located ventrally whereas the vertebrate spinal cords are located dorsally. There is debate amidst evolutionary biologists as to whether these dissimilar nervous system plans evolved separately or whether the invertebrate body program arrangement somehow "flipped" during the evolution of vertebrates.
Sentry this video of biologist Mark Kirschner discussing the "flipping" phenomenon of vertebrate evolution.
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Source: https://courses.lumenlearning.com/wm-biology2/chapter/diversity-of-nervous-systems/
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