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This organization demands a tight developmental control and the formation of a variety of specialized zones of contact between different areas of the myelinating cell membrane. Each node of Ranvier is flanked by paranodal regions where helicoidally wrapped glial loops are attached to the axonal membrane by a septate-like junction.
Myelin is formed by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system.Therefore, the first stage of myelinogenesis is often defined as the differentiation of oligodendrocyte progenitor cells (OPCs) or Schwann cell progenitors into their mature counterparts, [4] followed by myelin formation around axons.
The process of generating myelin is called myelination or myelinogenesis. In the CNS, oligodendrocyte progenitor cells (OPCs) differentiate into mature oligodendrocytes, which form myelin. In humans, myelination begins early in the 3rd trimester, [ 11 ] although only little myelin is present in either the CNS or the PNS at the time of birth.
Following terminal differentiation in vivo, mature oligodendrocytes wrap around and myelinate axons. In vitro , oligodendrocytes create an extensive network of myelin-like sheets. The process of differentiation can be observed both through morphological changes and cell surface markers specific to the discrete stage of differentiation, though ...
There are four subdivisions of group A nerve fibers: alpha (α) Aα; beta (β) Aβ; , gamma (γ) Aγ, and delta (δ) Aδ. These subdivisions have different amounts of myelination and axon thickness and therefore transmit signals at different speeds. Larger diameter axons and more myelin insulation lead to faster signal propagation.
The onset is gradual and uniform. The pathological findings of subacute combined degeneration consist of patchy losses of myelin in the dorsal and lateral columns. Patients present with weakness of the legs, arms, and trunk, and tingling and numbness that progressively worsens.
Protein shakes offer a simple way to boost protein intake, but not everyone needs to include them in their diets. Dietitians explain.
After hip replacement, hip prosthesis zones are regions in the interface between prosthesis material and the surrounding bone. These are used as reference regions when describing for example complications including hip prosthesis loosening on medical imaging .