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Myelination
Myelination, or myelinogenesis, is the formation and development of myelin sheaths in the nervous system, typically initiated in late prenatal neurodevelopment and continuing throughout postnatal development. The term ''myelinogenesis'' is also sometimes used to differentiate the very early stages of embryonic myelination. Myelin is formed by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. Myelination continues throughout the lifespan to support learning and memory via neural circuit plasticity as well as remyelination following injury. Successful myelination of axons increases action potential speed by enabling saltatory conduction, which is essential for timely signal conduction between spatially separate brain regions, as well as provides metabolic support to neurons. Stages Myelin is formed by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. Therefore, the first stage of m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oligodendrocyte
Oligodendrocytes (), also known as oligodendroglia, are a type of neuroglia whose main function is to provide the myelin sheath to neuronal axons in the central nervous system (CNS). Myelination gives metabolic support to, and insulates the axons of most vertebrates. A single oligodendrocyte can extend its Cellular extensions, processes to cover up to 40 axons, that can include multiple adjacent axons. The myelin sheath is segmented along the axon's length at gaps known as the nodes of Ranvier. In the peripheral nervous system the myelination of axons is carried out by Schwann cells. Oligodendrocytes are found exclusively in the CNS, which comprises the brain and spinal cord. They are the most widespread cell lineage, including oligodendrocyte progenitor cells, pre-myelinating cells, and mature myelinating oligodendrocytes in the CNS white matter. Non-myelinating oligodendrocytes are found in the grey matter surrounding and lying next to neuronal cell bodies. They are known as neu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oligodendrocytes
Oligodendrocytes (), also known as oligodendroglia, are a type of neuroglia whose main function is to provide the myelin sheath to neuronal axons in the central nervous system (CNS). Myelination gives metabolic support to, and insulates the axons of most vertebrates. A single oligodendrocyte can extend its processes to cover up to 40 axons, that can include multiple adjacent axons. The myelin sheath is segmented along the axon's length at gaps known as the nodes of Ranvier. In the peripheral nervous system the myelination of axons is carried out by Schwann cells. Oligodendrocytes are found exclusively in the CNS, which comprises the brain and spinal cord. They are the most widespread cell lineage, including oligodendrocyte progenitor cells, pre-myelinating cells, and mature myelinating oligodendrocytes in the CNS white matter. Non-myelinating oligodendrocytes are found in the grey matter surrounding and lying next to neuronal cell bodies. They are known as neuronal satellite ce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myelinated Neuron
Myelin Sheath ( ) is a lipid-rich material that in most vertebrates surrounds the axons of neurons to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. The myelinated axon can be likened to an electrical wire (the axon) with insulating material (myelin) around it. However, unlike the plastic covering on an electrical wire, myelin does not form a single long sheath over the entire length of the axon. Myelin ensheaths part of an axon known as an internodal segment, in multiple myelin layers of a tightly regulated internodal length. The ensheathed segments are separated at regular short unmyelinated intervals, called nodes of Ranvier. Each node of Ranvier is around one micrometre long. Nodes of Ranvier enable a much faster rate of conduction known as saltatory conduction where the action potential recharges at each node to jump over to the next node, and so on till it reaches the axon terminal. At the terminal the actio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Action Potential
An action potential (also known as a nerve impulse or "spike" when in a neuron) is a series of quick changes in voltage across a cell membrane. An action potential occurs when the membrane potential of a specific Cell (biology), cell rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of Membrane potential#Cell excitability, excitable cells, which include animal cells like neurons and myocyte, muscle cells, as well as some plant cells. Certain endocrine cells such as pancreatic beta cells, and certain cells of the anterior pituitary gland are also excitable cells. In neurons, action potentials play a central role in cell–cell interaction, cell–cell communication by providing for—or with regard to saltatory conduction, assisting—the propagation of signals along the neuron's axon toward axon terminal, synaptic boutons situated at the ends of an axon; these signals can then connect wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axon
An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences) is a long, slender cellular extensions, projection of a nerve cell, or neuron, in Vertebrate, vertebrates, that typically conducts electrical impulses known as action potentials away from the Soma (biology), nerve cell body. The function of the axon is to transmit information to different neurons, muscles, and glands. In certain sensory neurons (pseudounipolar neurons), such as those for touch and warmth, the axons are called afferent nerve fibers and the electrical impulse travels along these from the peripheral nervous system, periphery to the cell body and from the cell body to the spinal cord along another branch of the same axon. Axon dysfunction can be the cause of many inherited and acquired neurological disorders that affect both the Peripheral nervous system, peripheral and Central nervous system, central ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saltatory Conduction
In neuroscience, saltatory conduction () is the propagation of action potentials along myelinated axons from one node of Ranvier to the next, increasing the conduction velocity of action potentials. The uninsulated nodes of Ranvier are the only places along the axon where ions are exchanged across the axon membrane, regenerating the action potential between regions of the axon that are insulated by myelin, unlike electrical conduction in a simple circuit. Mechanism Myelinated axons only allow action potentials to occur at the unmyelinated nodes of Ranvier that occur between the myelinated internodes. It is by this restriction that saltatory conduction propagates an action potential along the axon of a neuron at rates significantly higher than would be possible in unmyelinated axons (150 m/s compared from 0.5 to 10 m/s). As sodium rushes into the node it creates an electrical force which pushes on the ions already inside the axon. This rapid conduction of electrical s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Node Of Ranvier
Nodes of Ranvier ( ), also known as myelin-sheath gaps, occur along a myelinated axon where the axolemma is exposed to the extracellular space. Nodes of Ranvier are uninsulated axonal domains that are high in sodium and potassium ion channels complexed with cell adhesion molecules, allowing them to participate in the exchange of ions required to regenerate the action potential. Nerve conduction in myelinated axons is referred to as saltatory conduction () due to the manner in which the action potential seems to "jump" from one node to the next along the axon. This results in faster conduction of the action potential. The nodes of Ranvier are present in both the Peripheral nervous system, peripheral and Central nervous system, central nervous systems. Overview The nodes are primarily composed of sodium and potassium voltage-gated ion channels; Cell adhesion molecule, CAMs such as neurofascin-186 and NRCAM, NrCAM; and cytoskeletal adaptor proteins such as Ankyrin, ankyrin-G and Sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Remyelination
Remyelination is the process of propagating oligodendrocyte precursor cells to form oligodendrocytes to create new myelin sheaths on demyelinated axons in the Central nervous system (CNS). This is a process naturally regulated in the body and tends to be very efficient in a healthy CNS. The process creates a thinner myelin sheath than normal, but it helps to protect the axon from further damage, from overall degeneration, and proves to increase conductance once again. The processes underlying remyelination are under investigation in the hope of finding treatments for demyelinating diseases, such as multiple sclerosis. As of 2022 the status of possible remyelination acceleration is of trials only, with side effects of possible drugs one limiting issue. Function Remyelination is activated and regulated by a variety of factors surrounding lesion sites that control the migration and differentiation of Oligodendrocyte Precursor Cells. Remyelination looks different from developmental ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thyroid Hormone
File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones triiodothyronine, T3 and T4 rect 376 268 820 433 Thyroid-stimulating hormone rect 411 200 849 266 Thyrotropin-releasing hormone rect 297 168 502 200 Hypothalamus rect 66 216 386 256 Anterior pituitary, Anterior pituitary gland rect 66 332 342 374 Negative feedback rect 308 436 510 475 Thyroid, Thyroid gland rect 256 539 563 635 Thyroid hormones rect 357 827 569 856 Catecholamine rect 399 716 591 750 Metabolism desc bottom-left Thyroid hormones are two hormones produced and released by the thyroid gland, triiodothyronine (T3) and thyroxine (T4). They are tyrosine-based hormones that are primarily responsible for regulation of metabolism. T3 and T4 are partially composed of iodine, derived from food. A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid, thyroid tissue and will cause the disease known as simple goitre. The major form of thyroid hormone in the blood ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thyroid Hormone Receptor Alpha
Thyroid hormone receptor alpha (TR-alpha) also known as nuclear receptor subfamily 1, group A, member 1 (NR1A1), is a nuclear receptor protein that in humans is encoded by the ''THRA'' gene. Function The protein encoded by this gene is a nuclear hormone receptor for triiodothyronine. It is one of the several receptors for thyroid hormone, and has been shown to mediate the biological activities of thyroid hormone. Knockout studies in mice suggest that the different receptors, while having certain extent of redundancy, may mediate different functions of thyroid hormone. Alternatively spliced transcript variants encoding distinct isoforms have been reported. Role in pathology Mutations of the THRA gene may cause nongoitrous congenital hypothyroidism-6, a subtype of congenital hypothyroidism. Interactions THR1 has been shown to interact with: * COPS2, * EP300, * ITGB3BP, * MED1, * MED6, * MED12, * MED16, * MEF2A, * NCOA6, * TRIP11, and * UBC The University ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
