1 of or relating to the nervous system; "nervous disease"; "neural disorder" [syn: nervous]
The nervous system is a highly specialized network whose principal components are nerves called neurons. Neurons are interconnected to each other in complex arrangements and have the property of conducting, using electrochemical signals, and a great variety of stimuli both within the nervous tissue as well as from and towards most of the other tissues. Thus, neurons coordinate multiple functions in organisms. Nervous systems are found in many multicellular animals but differ greatly in complexity between species.
Nervous system in humansThe human nervous system can be grouped into both with gross anatomy, (which describes the parts that are large enough to be seen with the naked eye,) and microanatomy, (which describes the system at a cellular level.) At gross anatomy, the nervous system can be grouped in distinct organs, these being actually stations which the neural pathways cross through. Thus, with a didactical purpose, these organs, according to their ubication, can be divided in two parts: the central nervous system (CNS) and the peripheral nervous system (PNS).
Central nervous systemThe central nervous system (CNS) represents the largest part of the nervous system, including the brain and the spinal cord. The CNS is contained within the dorsal cavity, with the brain within the cranial cavity, and the spinal cord in the spinal cavity. The CNS is covered by the meninges. The brain is also protected by the skull, and the spinal cord is also protected by the vertebrae. The nervous system can be connected into many systems that can function together. The two systems are central nervous system (CNS) and the peripheral nervous system (PNS).
Central nervous system Brain Prosencephalon Telencephalon Rhinencephalon, Amygdala, Hippocampus, Neocortex, Lateral ventricles
Diencephalon Epithalamus, Thalamus, Hypothalamus, Subthalamus, Pituitary gland, Pineal gland, Third ventricle
Peripheral nervous systemThe PNS consists of all the other nervous structures that do not lie in the CNS. The large majority of what are commonly called nerves (which are actually axonal processes of nerve cells) are considered to be PNS.
MicroanatomyThe nervous system is, on a small scale, primarily made up of neurons. However, glial cells also play a major role.
NeuronsThey are the core components of both the central nervous system & peripheral nervous system. Neurons are sensors that send electric messages to the Central Nervous System which send the electric messages back to the neurons telling them how to react, where the messages are finally sent back directly to the brain. These messages travel at a usual pace of 100 meters per second.
Glial cellsGlial cells are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin, and participate in signal transmission in the nervous system. In the human brain, glia are estimated to outnumber neurons by about 10 to 1.
Glial cells provide support and protection for neurons. They are thus known as the "glue" of the nervous system. The four main functions of glial cells are to surround neurons and hold them in place, to supply nutrients and oxygen to neurons, to insulate one neuron from another, and to destroy pathogens and remove dead neurons.
A less anatomical but much more functional division of the human nervous system is that classifying it according to the role that the different neural pathways play, regardless whether these cross through the CNS or the PNS:
The somatic nervous system is responsible for coordinating the body's movements, and also for receiving external stimuli. It is the system that regulates activities that are under conscious control.
Of digestion, it regulates from the esophagus to the stomach, small intestine and colon.
In turn, these pathways can be divided according to the direction in which they conduct stimuli:
However, there are relay neurons in the CNS as well.
The junction between two neurones is called a synapse. There is a very narrow gap (about 20nm in width) between the neurons - the synaptic cleft, where an action potential is transmitted from one neuron to a neighboring one. They do this by relaying the message with the use of neurotransmitters which the next neuron then receives the electrical signal, known as a nerve impulse. The nerve impulse is determined by the neurotransmitter to then carry the message to its appropriate destination. These nerve impulses are a change in ion balance in the nerve cell, which the central nervous system can then interpret. The fact that the nervous system uses a mixture of electrical and chemical signals makes it incredibly fast, which is necessary to acknowledge the presence of danger. For example, a hand touching a hot stove. If the nervous system was only comprised of chemical signals, the body would not tell the arm to move fast enough to escape dangerous burns. So the speed of the nervous system is a necessity for life.
DevelopmentSome landmarks of embryonic neural development include the birth and differentiation of neurons from stem cell precursors, the migration of immature neurons from their birthplaces in the embryo to their final positions, outgrowth of axons from neurons and guidance of the motile growth cone through the embryo towards postsynaptic partners, the generation of synapses between these axons and their postsynaptic partners, and finally the lifelong changes in synapses which are thought to underlie learning and memory.
ImportanceMany people have lost basic motor skills and other skills because of spinal cord injuries. If this portion is damaged, the biggest nerve and the most important one gets damaged. This leads to paralysis or other permanent damage.
AbilitiesThe nervous system is able to make basic motor skills and other skills possible. The basic 5 senses of texture, taste, sight, smell, and hearing are powered by the nervous system. If disabled, basic motor skills may be lost.
VertebratesThe nervous system of all vertebrate animals, is often divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord.
WormsPlanaria, a type of flatworm, have dual nerve cords running along the length of the body and merging at the tail and the mouth. These nerve cords are connected by transverse nerves like the rungs of a ladder. These transverse nerves help coordinate the two sides of the animal. Two large ganglia at the head end function similar to a simple brain. Photoreceptors on the animal's eyespots provide sensory information on light and dark.
The nervous system of the roundworm Caenorhabditis elegans has been mapped out to the cellular level. Every neuron and its cellular lineage has been recorded and most, if not all, of the neural connections are known. In this species, the nervous system is sexually dimorphic; the nervous systems of the two sexes, males and hermaphrodites, have different numbers of neurons and groups of neurons that perform sex-specific functions. In C. elegans, males have exactly 383 neurons, while hermaphrodites have exactly 302 neurons http://www.wormbook.org/chapters/www_specnervsys/specnervsys.html
Arthropods, such as insects and crustaceans, have a nervous system made up of a series of ganglia, connected by a ventral nerve cord made up of two parallel connectives running along the length of the belly http://www.entomology.umn.edu/cues/4015/morpology/. Typically, each body segment has one ganglion on each side, though some ganglia are fused to form the brain and other large ganglia http://www.cals.ncsu.edu/course/ent425/tutorial/nerves.html.
The head segment contains the brain, also known as the supraesophageal ganglion. In the insect nervous system, the brain is anatomically divided into the protocerebrum, deutocerebrum, and tritocerebrum. Immediately behind the brain is the subesophageal ganglion, which is composed of three pairs of fused ganglia. It controls the mouthparts, the salivary glands and certain muscles.
Many arthropods have well-developed sensory organs, including compound eyes for vision and antennae for olfaction and pheromone sensation. The sensory information from these organs is processed by the brain.
DevelopmentNeural development in most species have many similarities neural development in humans.
neural in Arabic: جهاز عصبي
neural in Bulgarian: Нервна система
neural in Catalan: Sistema nerviós
neural in Czech: Nervová soustava
neural in Danish: Nervesystemet
neural in German: Nervensystem
neural in Dhivehi: ނާރުތަކުގެ ނިޒާމް
neural in Estonian: Närvisüsteem
neural in Modern Greek (1453-): Νευρικό σύστημα
neural in English: Nervous system
neural in Spanish: Sistema nervioso
neural in Esperanto: Nerva sistemo
neural in Basque: Nerbio-sistema
neural in Persian: دستگاه عصبی
neural in French: Système nerveux
neural in Galician: Sistema nervioso
neural in Croatian: Živčani sustav
neural in Ido: Nervaro
neural in Indonesian: Sistem saraf
neural in Icelandic: Taugakerfið
neural in Italian: Sistema nervoso
neural in Hebrew: מערכת העצבים
neural in Pampanga: Sistema nerviosa
neural in Latvian: Nervu sistēma
neural in Lithuanian: Nervų sistema
neural in Macedonian: Нервен систем
neural in Dutch: Zenuwstelsel
neural in Japanese: 神経系
neural in Norwegian: Nervesystemet
neural in Norwegian Nynorsk: Nervesystemet
neural in Polish: Układ nerwowy człowieka
neural in Portuguese: Sistema nervoso
neural in Romanian: Sistem nervos
neural in Quechua: Ankucha llika
neural in Russian: Нервная система
neural in Albanian: Sistemi nervor
neural in Simple English: Nervous system
neural in Slovak: Nervové tkanivo
neural in Slovenian: Živčni sistem
neural in Serbian: Нервни систем
neural in Finnish: Hermosto
neural in Swedish: Nervsystemet
neural in Tagalog: Sistemang nerbiyos
neural in Thai: ระบบประสาท
neural in Turkish: Sinir sistemi
neural in Ukrainian: Нервова система
neural in Urdu: عصبی نظام
neural in Chinese: 神经系统