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Case 1.14
Published in Monica Fawzy, Plastic Surgery Vivas for the FRCS(Plast), 2023
Saltatory conduction allows the action potentials to transmit along the only uninsulated areas along the axon, termed the nodes of Ranvier, to speed transmission from 10 m/s in an unmyelinated nerve to 150 m/s in a myelinated nerve.
Diseases of the Peripheral Nerve and Mononeuropathies
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Diana Mnatsakanova, Charles K. Abrams
Myelinated fibers: Schwann cells produce myelin. Their membranes wrap around the axon to form the myelin sheath.Nodes of Ranvier – interruptions in the myelin sheath. Action potentials propagate from one node to the next with the rate roughly proportional to the fiber diameter.> 1 μm in diameter in the PNS.Largest and fastest conducting fibers.Motor and sensory nerves have myelinated fibers. The sensory modalities include proprioception, position sense, and touch sensation.
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 therapeutic effect of nano-zinc on the optic nerve of offspring rats and their mothers treated with lipopolysaccharides
Published in Egyptian Journal of Basic and Applied Sciences, 2023
Eman Mohammed Emara, Hassan Ih El-Sayyad, Amr M Mowafy, Heba a El-Ghaweet
The optic nerve (cranial nerve II) is a central nervous system (CNS) tract that passes through the optic canal to leave the orbit. It is made up of the retinal ganglion cells (RGCs) axons. It allows vision by transmitting neural impulses from the retina to the brain. It is divided into four sections: the intraocular nerve head, the intraorbital, the intracanalicular and the intracranial [6]. The types of glial cells in the optic nerve are oligodendrocytes, astrocytes and microglia. Oligodendrocytes are responsible for producing the myelin sheaths that protect the CNS axons and contact nodes of Ranvier as well as they are the locations where action potentials are propagated and axonal integrity. Astrocytes are responsible for numerous physiological and pathological activities such as potassium homeostasis and metabolism as well as reactive astrogliosis in response to CNS trauma. Microglia are immune cells in CNS and have a significant impact on inflammation and infections [7].
Regenerative replacement of neural cells for treatment of spinal cord injury
Published in Expert Opinion on Biological Therapy, 2021
William Brett McIntyre, Katarzyna Pieczonka, Mohamad Khazaei, Michael G. Fehlings
The compressive forces that accompany spinal cord insults are also responsible for oligodendrocyte necrosis and necroptosis within days of the injury, eventually contributing to myelin damage [10,11]. As the injury progresses, accumulation of cytotoxic factors in the microenvironment causes oligodendrocytes to undergo apoptosis in a similar manner to neurons. This ultimately eradicates the associated myelin sheath [11,12]. ROS in the microenvironment can react with the lipids in the cell membrane of myelinating oligodendrocytes and results in the oxidative degradation and peroxidation of lipids (reviewed by Plemel et al. [12]). The products of lipid peroxidation interact with membrane receptors and transcription factors/repressors to induce signaling for apoptosis. This can stimulate the activation of both the intrinsic and extrinsic apoptotic signaling pathways [13]. Moreover, disorganization of the nodes of Ranvier occurs through the diffusion of nodal, paranodal and juxtaparanodal ion channels within hours of the injury, and is found to persist at 6 weeks following injury, ultimately disrupting signal transduction [14,15]. The denuded axons that have lost their metabolic and protective support from the associated myelin sheath are also vulnerable to Wallerian degeneration, which degenerates the neurons that had otherwise been spared during the initial traumatic mechanical insult [16].
A blend containing docosahexaenoic acid, arachidonic acid, vitamin B12, vitamin B9, iron and sphingomyelin promotes myelination in an in vitro model
Published in Nutritional Neuroscience, 2020
Jonas Hauser, Sébastien Sultan, Andreas Rytz, Pascal Steiner, Nora Schneider
In the CNS, each step of myelination, including proliferation of OPCs, differentiation and maturation of OPCs into myelinating OLs as well as myelin sheath formation is highly regulated by extrinsic and intrinsic factors. Neuronal activity modulates the thickness of the myelin sheaths as well as the number of nodes of Ranvier [14]. Neuronal and astrocytic derived factors (e.g. growth factors, signalling molecules and neurotransmitters) actively participate to control each step of myelination [6,15]. Additionally, environmental factors might influence developmental myelination in the human brain. In particular, varied available infant nutritional compositions exhibited differing effects on myelination, suggesting that early life nutrition may be of importance for the regulation of myelination [7]. Therefore, identifying early life nutritional factors that support myelination is of critical importance for optimal brain and cognitive development.