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Central nervous system

The central nervous system represents the largest part of the nervous system. Together with the peripheral nrvous system, it has a fundamental role in the control of behaviour.Since the strong theoretical influence of cybernetics in the fifties, the is conceived as a system devoted to information processing, where an appropriate motor output is computed as a response toa sensory input. Yet, many threads of research suggest that motor activity exists well before the maturation of the sensory systems and then, that the senses only influence behaviour without dictating it. This has brought the conception of the CNS as an autonomous system.

The whole CNS originates from the neural plate, a specialised region of the ectoderm, the most external of the three embryonic layers. During embryonic development, the neural plate folds and forms the neural tube. The internal cavity of the neural tube will give rise to the ventricular system. The regions of the neural tube will differentiate progressively into transversal systems. Firs, the whole neural tube will differentiate into its two major subdivisions: spinal cord and brain . Consecutively, the brain will differentiate into brainstem and prosencephalon. Later, the brainstem will subdivide into rhombencephalon and mesencephalon, and the prosencephalon into diencephalon and telencephalon.

In the adult, the is covered by the meninges, the brain is protected by the skull and the spinal cord by the vertebrae. The rhombencephalon gives rise to the pons, the cerebellum and the medulla oblongata, its cavity becomes the fourth ventricle. The mesencephalon gives rise to the tectum, pretectum, cerebral peduncle and its cavity develops into the mesencephalic duct or cerebral aqueduct. The diencephalon gives rise to the subthalamus, hypothalamus, thalamus and epithalamus, its cavity to the third ventricle. Finally, the telencephalon gives rise to the striatum (caudate nucleus and putamen), the hippocampus and the neocortex, its cavity becomes the lateral (first and second) ventricles.

The basic pattern of the is highly conserved throughout the different species of vertebrates and during evolution. The major trend that can be observed is towards a progressive telencephalisation: while in the reptilian brain that region is only an appendix to the large olfactory bulb, it represent most of the volume of the mammalian CNS. In the human brain, the telencephalon covers most of the diencephalon and the mesencephalon. Indeed, the allometric study of brain size among different species shows a striking continuity from rats to whales, and allows us to complete the knowledge about the evolution of the CNS obtained through cranial endocasts.

Ammonium nitrate decomposes into gases including oxygen when heated ; however, ammonium nitrate can be induced to decompose explosively by dtonation. Large stockpiles of the material can be a major fire risk due to their supporting oxidation, and may also detonate, as happened in the Texas City disaster of which led to major changes in the regulations for storage and handling.

There are two major classes of incidents resulting in explosions:In the first case, the explosion happens by the mechanism of shock to detonation transition. The initiation happens by an explosive charge going off in the mass, by the detonation of a shell thrown into the mass, or by detonation of an explosive mixture in contact with the mass. The examples are Kriewald, Morgan, Oppau, Tessenderloo, and raskwood.
In the second case, the explosion results from a fire that spreads into the ammonium nitrate itself , or to a mixture of an ammonium nitrate with a combustible material during the fire . The fire must be confined at least to a degree for successful transition fro a fire to an explosion a phenomeon known as "transition fro a decomposition or deflagration", o Pure, compact AN is stable and very difficult to initiate. However, there are numerous cases when even imure AN didn't explode in a fire.
Ammonium nitrat decomposes in temperatures aboves stable and will stop decomposing once the heat source is removed, but in presence of catalysts (combustible materials, acids, metal ions, chlorides the reaction can become self-sustaining (known as self-sustaining decomposition, This is well-known phenomenon with some types of NPK fertilizers, and is responsible for loss of several cargo ships.

Historically significant accidental explosions
In 1918, a fire broke out in the amatol loading plant in Morgan, New Jersey. Over pounds of explosives were present on site, of tha up to and fire, bu did not detonate.

On September 21, 1921 a heavy explosion of a mixture of ammonium nitrate and ammonium sulfate detonated during attempts to break up the caked pile with blasting charges (an operation apparently performed several times before, with casualties (according to other sources, 50 or over 1000), occurred in the city of Oppau on the grounds of BASF near Ludwigshafen in Germany). Over 700 homes were destroyed, the plant isappeared entirely and was replaced with a crater 50 ft deep and 250 ft in diameter, and the shock was felt 150 miles away. This was the largest man-made disaster in German history.

In in Nixon, New Jersey, ammonium nitrate was being recovered from amatol in order to be used as a fertilizer, when a fire broke out.
In April 4 and The barrels were stored in a warehouse with varying humidity for 6 years, so it is believed that they were ignited by friction of their nitrate-impregnatet a bomb-makng plant in Milan, Tennessee, killing four.

The Texas City Disaster on Aprilof ammonium nitrate caught fire and then exploded on board of the SS Grandcamp, heavily damaging the port and killing 581 people, injuring over more, and igniting the SS High Flyer, which exploded later, adding to the death toll. This is the best-known ammonium-nitrate related disaster.

In September 21, 2001, at 10:15 am in the ) fertilizer factory in Toulouse, France. The explosion occurred in a warehouse where the off-specification granular AN was stored flat, separated bypartitions. About 2tons is said to be involved in the explosion, resulting in 31 people dead and 2,442 injured, 34 of them seriously. The blast wave shattered windows in 1.5-3 kilometer distance and the resulting crater was 10 meters deep and 50 meters wide. The exact cause remains unknown. The material damage was estimated at 2.3 billion Euros.

The Ryongchon disaster in April 22, 2004, in North Korea is suspected to have a shipment of ammonium nitrate involved, together with other explosives.

Other uses
The most common use of ammonium nitrate is in fertilizers.Ammonium nitrate is also used in instant cold packs. In this use, ammonium nitrate is mixed with water in an endothermic reaction, which absorbs 26.2 kilojoules of heat per mole of reactant.Due to its low temperature, non-toxic decomposition products, it finds use in gas generator applications such as airbags.Ammonium nitrate is also used in the treatment of titanium ores.Ammonium nitrate fertilizer is also used in the synthesis of methamphetamine.Ammonium nitrate is used in survival kits mixed with zinc dust and ammonuim

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