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The patient with acute neurological problems
Published in Peate Ian, Dutton Helen, Acute Nursing Care, 2020
Oligodendrocytes generate myelin within the CNS (see Figure 9.3). Schwann cells, also a type of glial cell, generate myelin in the PNS. Schwann cells wrap around axons, forming a myelin sheath. The outer layer includes the Schwann cell’s cytoplasm and nucleus and is called the neurolemma. The neurolemma is thought to promote axon regeneration in the PNS. When a myelinated axon is examined microscopically, there appear to be gaps in the myelin called nodes of Ranvier. One Schwann cell myelinates the segment of axon between two nodes of Ranvier; myelinated nerves will therefore have several Schwann cells (see Figures 9.3 and 9.4).
The Nervous System and Its Disorders
Published in Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss, Understanding Medical Terms, 2020
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss
Some axons are surrounded by a myelin sheath (neurilemma or neurolemma) consisting of the lipid substance myelin. The myelin sheath is discontinuous approximately every millimeter at the neurofibril nodes, also called the nodes of Ranvier. The myelin serves as an electrical insulator, forcing the impulse to jump from one node to another, which functions to increase the speed of conduction in a myelinated nerve and decrease the energy required for transmission. Further, the larger a nerve is, the more quickly it can conduct impulses. Because of their speed of conduction, large myelinated nerves are the primary conductors of impulses to skeletal muscles, allowing the rapid responses
Experimental Stomatology
Published in Samuel Dreizen, Barnet M. Levy, Handbook of Experimental Stomatology, 2020
Samuel Dreizen, Barnet M. Levy
There were no gross differences in the appearance of the tongue between the test and control animals. Histologically, thiamine deficiency with or without salivary gland duct ligation, precipitated changes in both the nerves and muscles of the tongue. The perineurium was disrupted, many neurilemma tubes were empty of myelin, axis cylinders were fragmented, and Schwann cells manifested dark staining of the nuclei. Striated muscles became atrophied and lost their banding. The sarcolemma was disorganized, and muscle fiber nuclei became pyknotic. In addition to the neuromuscular damage in the tongue, the deficient animals displayed marked growth retardation and a change in fur color.
Effects of Theranekron and alpha-lipoic acid combined treatment on GAP-43 and Krox-20 gene expressions and inflammation markers in peripheral nerve injury
Published in Ultrastructural Pathology, 2021
Leman Sencar, Gülfidan Coşkun, Dilek Şaker, Tuğçe Sapmaz, Samet Kara, Alper Çelenk, Sema Polat, Derviş Mansuri Yılmaz, Y. Kenan Dağlıoğlu, Sait Polat
Following injury, serious histological changes are observed in the distal and proximal part of the peripheral nerve. It is known that during the first 6 hours, the nucleus migrates to the periphery and the Nissl bodies undergo chromatolysis in the neuron cell body. Distal occurs to the damaged area in the axonal cytoskeleton and myelin sheath, and Wallerian degeneration occurs as a result of fragmentation and degeneration.5,9 As a result, in the first 48–96 hours it was determined that the axon continuity disrupted and impulse transmission was impaired. The regeneration process begins after phagocytosis of myelin sheath and axon debris by Schwann cells and macrophages.4,7 As Schwann cells form the Büngner bands that guide the formed axon sprouts, the axon starts growing at a rate of 1–3 mm per day in the neurilemma tube.6 Furthermore, significant structural changes are also observed in the proximal segment of the nerve close to the damaged area.4
The leptin receptor mutation of the obese Zucker rat causes sciatic nerve demyelination with a centripetal pattern defect
Published in Ultrastructural Pathology, 2018
Jacques Gilloteaux, Kritika Subramanian, Nadia Solomon, Charles Nicaise
In these fibers, the neurolemnocyte or SC cytoplasm of some small or large nerve fibers reveals typical indent of the perikaryal areas (not shown here); it contains typical cell organelles. The SC nucleus, with its perikaryon, is in the median internode regions of each peripheral nerve fiber, thus the internodal cytoplasm is most often viewed as a narrow band with the random TEM sections, named Cajal band. This ‘band’ of the SC contains the abaxonal region with its outermost myelin layer and sheaths where, by place, outer mesaxons can be viewed (Figures 1(c) and 2(a,b)). The axoplasms show mitochondria, neurotubules, neurofibrils, and a few adaxonal neuroreticulum cisternae. In the rat tibial branches, most nerve fibers are typically myelinated and organized by SCs in concentric tight layers of neurilemma forming an electron dense Fermat-like spire enclosing the neurites, whether found in cross or oblique, or low-magnification sections (Figure 3(a)).
Development of polypyrrole/collagen/nano-strontium substituted bioactive glass composite for boost sciatic nerve rejuvenation in vivo
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Bo Lin, Guoqing Dun, Dongzhu Jin, Yaowu Du
TEM was utilized to watch the ultra-structural morphology of recovered nerves. Fascicles with various sizes, each comprises of a few layers of axons, fibroblasts and enclosed SCs in the majority of the gatherings (Figure 5(d–f)). Myelin sheath thickness was fundamentally more noteworthy in the fibroblasts and enclosed SCs bunch than in the PPY/Coll/n-Sr@BG gathering. While the thicknesses of the control and PPY/Coll gatherings were comparative, they were unmistakably not exactly those seen in the other two gatherings [39]. To more readily assess the recuperation of harmed nerves, the centre fragment of recovered nerves was coloured with H&E re-coloring 24 weeks after the careful activity. All rodents were healthy and no passings were accounted for; wound disease and extreme tissue responses occurred amid the recuperation. Veins existed in the composite course gatherings (Figure 5(d–f)), which demonstrated that the veins produce and give supplements to harmed nerves amid the procedure of recuperation. Neurilemma cell existed in the three gatherings and advanced the development of harmed nerves. The myelinated fibre in 5 g and 5 h were appropriated in course of action with slender myelin cover in a manner and most unpredictable connective tissues in development. The fibre of recovered nerves in Figure 5(i) is increasingly roundabout fit as a fiddle, better-proportioned in size and orchestrated more thickly than in Figure 5(g,h). There are an expansive number of fascicular structures dispersed all through nerves in Figure 5(i). In light of the structural perception, the myelinated fibres in Figure 5(i) is more prominent in number and more concentrated than those in Figure 5(g,h) 24 weeks after implantation. Nerves were in more prominent extent in Figure 5(g–i), and this extent was near what was available in Figure 5(g–i).