Information about Nervous System

The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. Prominent parts of a nervous system include neurons and nerves, which are used in coordination. All parts of the nervous system are made of nervous tissue. The classification of the nervous system is mostly similar in humans as in other vertebrates.

Humans

The nervous system of humans is often divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord.

Central nervous system

Main article: Central nervous system

See also:

The central nervous system (CNS) represents the largest part of the nervous system, including the brain and the spinal cord. Together with the peripheral nervous system, it has a fundamental role in the control of behavior. The CNS is contained within the dorsal cavity, with the brain within the cranial subcavity, 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.

Central nervous system	Brain	Prosencephalon	Telencephalon	Rhinencephalon, Amygdala, Hippocampus, Neocortex, Lateral ventricles
			Diencephalon	Epithalamus, Thalamus, Hypothalamus, Subthalamus, Pituitary gland, Pineal gland, Third ventricle
		Brain stem	Mesencephalon	Tectum, Cerebral peduncle, Pretectum, Mesencephalic duct
			Rhombencephalon	Metencephalon	Pons, Cerebellum,
				Myelencephalon	Medulla oblongata
	Spinal cord

Peripheral nervous system

Main article: Peripheral nervous system

The PNS consists of all other nerves and neurons that do not lie within the CNS. The large majority of what are commonly called nerves (which are actually axonal processes of nerve cells) are considered to be PNS. The peripheral nervous system can be further classified either by direction of neurons and by function.

By direction

There are three types of directions of the neurones:

• Sensory system by sensory neurons, which carry impulses from a receptor to the CNS
• Efferent system by motor neurons, which carry impulses from the CNS to an effector
• Relay system by relay neurons (also called interneurons), which transmit impulses between the sensory and motor neurones. 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 between the neurones - the synaptic cleft.

By function

By function, the peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system.

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.

The autonomic nervous system is then split into the sympathetic division, parasympathetic division, and enteric division. The sympathetic nervous system responds to impending danger or stress, and is responsible for the increase of one's heartbeat and blood pressure, among other physiological changes, along with the sense of excitement one feels due to the increase of adrenaline in the system. The parasympathetic nervous system, on the other hand, is evident when a person is resting and feels relaxed, and is responsible for such things as the constriction of the pupil, the slowing of the heart, the dilation of the blood vessels, and the stimulation of the digestive and genitourinary systems. The role of the enteric nervous system is to manage every aspect of digestion, from the esophagus to the stomach, small intestine and colon.

Peripheral nervous system	by direction	sensory system
		efferent system
	By function	Somatic
		Autonomic	Sympathetic
			Parasympathetic
			Enteric

Vertebrates

The 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.

Worms

Planaria, 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 [1]

Arthropoda

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 [2]. Typically, each body segment has one ganglion on each side, though some ganglia are fused to form the brain and other large ganglia [3].

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.

See also

• Major systems of the human body
• Neural tissue
• Neural network
• Neuroendocrinology
• Neuroscience
• Neurotoxin
• Neural ensemble
• Somatic sensation

External links

• Neuroscience for Kids

Reference:

• Kimball's Biology Pages, CNS
• Kimball's Biology Pages, PNS

•  • [ e] Human organ systems
Cardiovascular system • Digestive system • Endocrine system • Immune system • Integumentary system • Lymphatic system • Muscular system • Nervous system • Reproductive system • Respiratory system • Skeletal system • Urinary system

•  • [ e] Nervous system
Central nervous system (Brain, Spinal cord) • Peripheral nervous system • Somatic nervous system • Autonomic nervous system (Sympathetic, Parasympathetic) • Enteric nervous system • Sensory system

•  • [ e] Nervous system, receptors: somatosensory system
Medial lemniscus	Touch/mechanoreceptors: Pacinian corpuscles • Meissner's corpuscles • Merkel's discs • Ruffini endings • Free nerve endings • Hair cells • Baroreceptor Proprioception: Golgi organ • Muscle spindle (Intrafusal muscle fiber • Nuclear chain fiber • Nuclear bag fiber)
Spinothalamic tract	Pain: Nociceptors Temperature: Thermoreceptors

•  • [ e] Prenatal development/Mammalian development of nervous system
General neural development/Neurulation	Neurula - Notochord - Neural folds - Neuroectoderm - Neural plate - Neural groove Neural crest - Neural tube (Neuromere/Rhombomere, Cephalic flexure)
Eye development	Optic vesicles - Optic stalk - Optic cup
Auditory development	Auditory vesicle - Auditory pit

•  • [ e] Histology: nervous tissue
Neurons (gray matter)	soma, axon (axon hillock, axoplasm, axolemma, neurofibril/neurofilament), dendrite (Nissl body, dendritic spine) types (bipolar, pseudounipolar, multipolar, pyramidal, Purkinje, granule)
Afferent nerve/Sensory nerve/Sensory neuron	GSA, GVA, SSA, SVA, fibers Ia, Ib or Golgi, II or Aβ, III or Aδ or fast pain, IV or C or slow pain
Efferent nerve/Motor nerve/Motor neuron	GSE, GVE, SVE, Upper motor neuron, Lower motor neuron (Aα motorneuron, Aγ motorneuron)
Synapses	neuropil, synaptic vesicle, neuromuscular junction, electrical synapse - Interneuron (Renshaw)
Sensory receptors	Free nerve ending, Meissner's corpuscle, Merkel nerve ending, Muscle spindle, Pacinian corpuscle, Ruffini ending, Olfactory receptor neuron, Photoreceptor cell, Hair cell, Taste bud
Glial cells	astrocyte, oligodendrocyte, ependymal cells, microglia, radial glia
Myelination (white matter)	Schwann cell, oligodendrocyte, nodes of Ranvier, internode, Schmidt-Lanterman incisures, neurolemma
Related connective tissues	epineurium, perineurium, endoneurium, nerve fascicle, meninges

•  • [ e] Nervous system pathology, primarily CNS (, )
Inflammatory diseases of the CNS	Meningitis (Arachnoiditis) - Encephalitis - Myelitis - Encephalomyelitis (Acute disseminated) - Tropical spastic paraparesis
Systemic atrophies primarily affecting the CNS	Huntington's disease - Spinocerebellar ataxia (Friedreich's ataxia, Ataxia telangiectasia, Hereditary spastic paraplegia) Spinal muscular atrophy: Werdnig-Hoffman disease - Kugelberg-Welander disease - Fazio Londe syndrome - MND (Amyotrophic lateral sclerosis (ALS), Progressive muscular atrophy (PMA), Progressive bulbar, Pseudobulbar, PLS)
Extrapyramidal and movement disorders	Parkinson's disease - Neuroleptic malignant syndrome - Postencephalitic parkinsonism - Pantothenate kinase-associated neurodegeneration - Progressive supranuclear palsy - Striatonigral degeneration - Dystonia (Spasmodic torticollis, Meige's syndrome, Blepharospasm) - Essential tremor - Myoclonus - Chorea - Restless legs syndrome - Stiff person syndrome
Other degenerative / demyelinating diseases	Alzheimer's disease - Pick's disease - Alpers' disease - Dementia with Lewy bodies - Leigh's disease - Multiple sclerosis - Devic's disease - Central pontine myelinolysis - Transverse myelitis
Seizure/epilepsy	Focal (Simple partial, Complex partial) - Generalised (Tonic-clonic, Absence, Atonic, Benign familial neonatal) - Lennox-Gastaut - West - Epilepsia partialis continua - Status epilepticus (Complex partial status epilepticus)
Headache	Migraine (Familial hemiplegic) - Cluster - Vascular - Tension
Vascular	Transient ischemic attack (Amaurosis fugax, Transient global amnesia) - Cerebrovascular disease (MCA, ACA, PCA, Foville's syndrome, Millard-Gubler syndrome, Lateral medullary syndrome, Weber's syndrome, Lacunar stroke)
Sleep disorders	Insomnia - Hypersomnia - Sleep apnea (Ondine's curse) - Narcolepsy - Cataplexy - Kleine-Levin syndrome
Other	Hydrocephalus (Normal pressure) - Idiopathic intracranial hypertension - Encephalopathy - Brain herniation - Cerebral edema - Reye's syndrome - Syringomyelia - Syringobulbia - Spinal cord compression

•  • [ e] Global structure in Systems, Systems sciences and Systems scientists
Categories
Systems	Biological system Complex system Complex adaptive system Conceptual system Cultural system Dynamical system Economic system Ecosystem Formal system Global Positioning System Human organ systems Information systems Legal system Metric system Nervous system Non-linear system Operating system Physical system Political system Sensory system Social system Solar System System Systems of measurement
Fields of theory	Chaos theory Complex systems Control theory Cybernetics Holism in science Sociotechnical systems theory Systems biology Systems dynamics Systems ecology Systems engineering Systems theory Systems science
Systems scientists	Russell L. Ackoff William Ross Ashby Gregory Bateson Ludwig von Bertalanffy Kenneth E. Boulding C. West Churchman Heinz von Foerster Charles Franois Jay Wright Forrester Ralph W. Gerard Debora Hammond George Klir Niklas Luhmann Humberto Maturana Donella Meadows Mihajlo D. Mesarovic Howard T. Odum Talcott Parsons Ilya Prigogine Anatol Rapoport Francisco Varela John N. Warfield Norbert Wiener