Difference between revisions of "Nervous system"
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| − | The '''nervous system''' is a network of specialized [[cells]] that coordinate the [[actions]] of an [[animal]] and send signals from one part of its [[body]] to another. These cells send signals either as electrochemical [[waves]] traveling along thin fibers called [ | + | The '''nervous system''' is a network of specialized [[cells]] that coordinate the [[actions]] of an [[animal]] and send signals from one part of its [[body]] to another. These cells send signals either as electrochemical [[waves]] traveling along thin fibers called [https://en.wikipedia.org/wiki/Axon axons], or as [[chemicals]] released onto other cells. The nervous system is composed of [https://en.wikipedia.org/wiki/Neuron neurons] and other specialized cells called [https://en.wikipedia.org/wiki/Glial_cells glial cells] (plural form glia). |
| − | In most [[animals]] the nervous system consists of two parts, central and peripheral. The [ | + | In most [[animals]] the nervous system consists of two parts, central and peripheral. The [https://en.wikipedia.org/wiki/Central_nervous_system central nervous system] contains the [[brain]] and spinal cord. The neurons of the central nervous system are interconnected in [[complex]] arrangements and [[transmit]] electrochemical signals from one to another. The [https://en.wikipedia.org/wiki/Peripheral_nervous_system peripheral nervous system] consists of sensory neurons, clusters of neurons called [https://en.wikipedia.org/wiki/Ganglia ganglia], and [https://en.wikipedia.org/wiki/Nerves nerves] connecting them to each other and to the central nervous system. Sensory neurons are activated by inputs impinging on them from outside or inside the [[body]], and send signals that inform the central nervous system of ongoing [[events]]. Motor neurons, situated either in the central nervous system or in peripheral ganglia, connect neurons to muscles or other effector organs. The interaction of the different neurons form neural circuits that regulate an [[organism]]'s [[perception]] of the world and its [[body]] and [[behavior]]. |
| − | Nervous systems are found in most multicellular [[animals]], but vary greatly in [[complexity]].[1] [ | + | Nervous systems are found in most multicellular [[animals]], but vary greatly in [[complexity]].[1] [https://en.wikipedia.org/wiki/Porifera Sponges] have no nervous system, although they have homologs of many genes that play crucial roles in nervous system function, and are capable of several whole-body responses, including a primitive form of locomotion. [https://en.wikipedia.org/wiki/Radiata Radiata], including jellyfish, have a nervous system consisting of a simple nerve net. [https://en.wikipedia.org/wiki/Bilaterian Bilaterian] animals, which include the great majority of vertebrates and invertebrates, all have a nervous system containing a brain, spinal cord, and peripheral nerves.[https://en.wikipedia.org/wiki/Nervous_system] |
==Function== | ==Function== | ||
At the most fundamental level, the [[function]] of the nervous system is to send [[signals]] from one part of the [[body]] to another. There are two basic ways that a cell can send signals to cells in other parts of the body. The simplest is by releasing [[chemicals]] called [[hormones]] into the internal circulation, so that they can diffuse to distant sites. In contrast to this "[[broadcast]]" mode of signaling, the nervous system provides "point-to-point" signals—neurons project their axons to specific target areas and make synaptic connections with specific target cells. Thus, neural signaling is in principle capable of a much higher level of [[precision]] than hormonal signaling. It is also much faster: the fastest nerve signals travel at speeds that can exceed 100 meters per second. | At the most fundamental level, the [[function]] of the nervous system is to send [[signals]] from one part of the [[body]] to another. There are two basic ways that a cell can send signals to cells in other parts of the body. The simplest is by releasing [[chemicals]] called [[hormones]] into the internal circulation, so that they can diffuse to distant sites. In contrast to this "[[broadcast]]" mode of signaling, the nervous system provides "point-to-point" signals—neurons project their axons to specific target areas and make synaptic connections with specific target cells. Thus, neural signaling is in principle capable of a much higher level of [[precision]] than hormonal signaling. It is also much faster: the fastest nerve signals travel at speeds that can exceed 100 meters per second. | ||
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Viewed at a higher level, the primary function of the nervous system is to control the [[body]]. One of the most important ways it does this is by extracting [[information]] from the environment using sensory receptors, sending signals that encode this information into the central nervous system, processing the information to determine an appropriate response, and finally sending signals via the peripheral nervous system to muscles or glands, in order to activate the response. | Viewed at a higher level, the primary function of the nervous system is to control the [[body]]. One of the most important ways it does this is by extracting [[information]] from the environment using sensory receptors, sending signals that encode this information into the central nervous system, processing the information to determine an appropriate response, and finally sending signals via the peripheral nervous system to muscles or glands, in order to activate the response. | ||
| − | The nervous system enables basic motor skills and [[Senses|sensing]]. The five classical senses (touch, taste, sight, smell, and hearing) are powered by the nervous system as are others such as [ | + | The nervous system enables basic motor skills and [[Senses|sensing]]. The five classical senses (touch, taste, sight, smell, and hearing) are powered by the nervous system as are others such as [https://en.wikipedia.org/wiki/Equilibrioception equilibrioception] (the sensing of [[gravity]]), [https://en.wikipedia.org/wiki/Nociception nociception] (the sensing of [[pain]]), and [https://en.wikipedia.org/wiki/Proprioception proprioception] (the sensing of [[relative]] limb location and [[motion]], as when [[touching]] the nose with closed eyes). Inhibition of these senses would retard basic motor skills. |
==See also== | ==See also== | ||
*'''''[[Neural Network]] | *'''''[[Neural Network]] | ||
== External links == | == External links == | ||
| − | * [ | + | * [https://faculty.washington.edu/chudler/introb.html Neuroscience for Kids] |
| − | * [ | + | * [https://www.thehumanbrainproject.org The Human Brain Project Homepage] |
| − | * [ | + | * [https://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CNS.html Kimball's Biology Pages, CNS] |
| − | * [ | + | * [https://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/PNS.html Kimball's Biology Pages, PNS] |
[[Category: Health]] | [[Category: Health]] | ||
[[Category: Biology]] | [[Category: Biology]] | ||
Latest revision as of 01:22, 13 December 2020
The nervous system is a network of specialized cells that coordinate the actions of an animal and send signals from one part of its body to another. These cells send signals either as electrochemical waves traveling along thin fibers called axons, or as chemicals released onto other cells. The nervous system is composed of neurons and other specialized cells called glial cells (plural form glia).
In most animals the nervous system consists of two parts, central and peripheral. The central nervous system contains the brain and spinal cord. The neurons of the central nervous system are interconnected in complex arrangements and transmit electrochemical signals from one to another. The peripheral nervous system consists of sensory neurons, clusters of neurons called ganglia, and nerves connecting them to each other and to the central nervous system. Sensory neurons are activated by inputs impinging on them from outside or inside the body, and send signals that inform the central nervous system of ongoing events. Motor neurons, situated either in the central nervous system or in peripheral ganglia, connect neurons to muscles or other effector organs. The interaction of the different neurons form neural circuits that regulate an organism's perception of the world and its body and behavior.
Nervous systems are found in most multicellular animals, but vary greatly in complexity.[1] Sponges have no nervous system, although they have homologs of many genes that play crucial roles in nervous system function, and are capable of several whole-body responses, including a primitive form of locomotion. Radiata, including jellyfish, have a nervous system consisting of a simple nerve net. Bilaterian animals, which include the great majority of vertebrates and invertebrates, all have a nervous system containing a brain, spinal cord, and peripheral nerves.[1]
Function
At the most fundamental level, the function of the nervous system is to send signals from one part of the body to another. There are two basic ways that a cell can send signals to cells in other parts of the body. The simplest is by releasing chemicals called hormones into the internal circulation, so that they can diffuse to distant sites. In contrast to this "broadcast" mode of signaling, the nervous system provides "point-to-point" signals—neurons project their axons to specific target areas and make synaptic connections with specific target cells. Thus, neural signaling is in principle capable of a much higher level of precision than hormonal signaling. It is also much faster: the fastest nerve signals travel at speeds that can exceed 100 meters per second.
Viewed at a higher level, the primary function of the nervous system is to control the body. One of the most important ways it does this is by extracting information from the environment using sensory receptors, sending signals that encode this information into the central nervous system, processing the information to determine an appropriate response, and finally sending signals via the peripheral nervous system to muscles or glands, in order to activate the response.
The nervous system enables basic motor skills and sensing. The five classical senses (touch, taste, sight, smell, and hearing) are powered by the nervous system as are others such as equilibrioception (the sensing of gravity), nociception (the sensing of pain), and proprioception (the sensing of relative limb location and motion, as when touching the nose with closed eyes). Inhibition of these senses would retard basic motor skills.
