Preganglionic Nerve Fibers

Preganglionic nerve fibers

Preganglionic Nerve Fibers 1

In the autonomic nervous system, fibers from the CNS to the ganglion are known as preganglionic fibers. All preganglionic fibers, whether they are in the sympathetic division or in the parasympathetic division, are cholinergic (that is, these fibers use acetylcholine as their neurotransmitter) and they are myelinated. Sympathetic preganglionic fibers tend to be shorter than parasympathetic preganglionic fibers because sympathetic ganglia are often closer to the spinal cord than are the parasympathetic ganglia. Another major difference between the two ANS (autonomic nervous systems) is divergence. Whereas in the parasympathetic division there is a divergence factor of roughly 1:4, in the sympathetic division there can be a divergence of up to 1:20. This is due to the number of synapses formed by the preganglionic fibers with ganglionic neurons.

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Frontopontine fibers

The frontopontine fibers are situated in the medial fifth of the base of the cerebral peduncles; they arise from the cells of the frontal lobe and then pass through the anterior limb of internal capsule at last end in the nuclei of the pons. The frontopontine tract (tractus frontopontinus) refers to the combination of the fibers.

Preganglionic Nerve Fibers 2

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Special finishes for synthetic fibers

Heat-setting of synthetic fabrics eliminates the internal tensions within the fiber, generated during manufacturing, and the new state can be fixed by rapid cooling. This heat setting fixes the fabrics in the relaxed state, and thus avoids subsequent shrinkage or creasing of the fabric. Presetting of goods makes it possible to use higher temperature for setting without considering the sublimation properties of dyes and also has a favorable effect on dyeing behavior and the running properties of the fabric. On the other hand, post-setting can be combined with some other operations such as Thermasol dyeing or optical brightening of polyester. Post-setting as a final finish is useful to achieve high dimensional stability, along with desired handle. Heat-setting is an important part in textile finishing. Stiffening and filling process: A stiffening effect is desirable in certain polyamides and polyester materials (e.g. petticoats, collar inner linings), which can be done by reducing the mutual independence of structural elements of fabric by polymer deposition on coating as a fine film. Certain products, based on modified (oxy-ethylated) polyamides, make the fabric more pleasant by reducing the cohesion of water so that it spreads over a larger area and thus evaporates more readily. Anti-pilling finish alleviates pilling, an unpleasant phenomenon associated with spun yarn fabrics, especially when they contain synthetics. Synthetic fibers are more readily brought to the surface of a fabric due to their smooth surface and circular cross-section, and due to their higher tensile strength and abrasion resistance. With knit "picking" also occurs: by abrasion, individual fibers work themselves out of yarn loops onto the surface, and the garment catches on a pointed or rough object. Knitting is susceptible to these effects due to the open weave and bulky yarn. Anti-static finish prevents dust from clinging to the fabric. Anti-static effective chemicals are largely chemically inert and require Thermasol or heat treatment for fixing on polyester fabrics. Polyether agents have been found to be useful but should not affect the dye-equilibrium on fiber, lest they impair the rubbing fastness. In general, Thermasol anti-static agents also have a good soil release action, which is as permanent as the anti-static effect. Anti-static finishes may also be of polyamide type, being curable at moderate temperatures. Non-slip finishes give the filaments a rougher surface. Synthetic warp and weft threads in loosely woven fabrics are particularly prone to slip because of their surface smoothness when the structure of fabric is disturbed and appearance is no longer attractive. Silica gel dispersions or silicic acid colloidal solutions are used in combination with latex polymer or acrylates dispersions to get more permanent effect, along with simultaneous improvement in resistance to pilling or snagging. These polymer finishes are also capable of imparting a soft and smooth handle to synthetic fabric without making it water repellent. Fire Resistant or Flame Retardant finish: to reduce flammability. Anti-microbial finish: with the increasing use of synthetic fibers for carpets and other materials in public places, anti-microbial finishes have gained importance. Products which are commonly applied are brominated phenols, quaternary ammonium compounds, organo-silver and tin compounds, which can be applied as solutions or dispersions. They can also be incorporated in a polymeric film deposited on the surface to achieve controlled release.

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