Search results
Results from the WOW.Com Content Network
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 basic protein (MBP) is a protein believed [weasel words] to be important in the process of myelination of nerves in the nervous system. The myelin sheath is a multi-layered membrane, unique to the nervous system, that functions as an insulator to greatly increase the velocity of axonal impulse conduction . [ 5 ]
In the brain, the processes of astrocytes form terminal endfeet, foot processes that help to form protective barriers in the brain. In the kidneys specialised cells called podocytes extend processes that terminate in podocyte foot processes that cover capillaries in the nephron .
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.
Myelination gives metabolic support to, and insulates the axons of most vertebrates. [1] A single oligodendrocyte can extend its processes to cover up to 40 axons, that can include multiple adjacent axons. [2] The myelin sheath is not continuous but is segmented along the axon's length at gaps known as the nodes of Ranvier.
Spontaneous myelin repair was first observed in cat models. [49] It was later discovered to occur in the human CNS as well, specifically in cases of multiple sclerosis (MS). [50] Spontaneous myelin repair does not result in morphologically normal oligodendrocytes and is associated with thinner myelin compared to axonal diameter than normal ...
Myelin sheath reduces membrane capacitance and increases membrane resistance in the inter-node intervals, thus allowing a fast, saltatory movement of action potentials from node to node. [l] [m] [n] Myelination is found mainly in vertebrates, but an analogous system has been discovered in a few invertebrates, such as some species of shrimp.