astrocytosis or sclerosis when a neuron is damaged astrocytes will form

Astrocytosis or sclerosis when a neuron is damaged

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astrocytosis or sclerosis – when a neuron is damaged, astrocytes will form hardened scar tissue and fill the space formerly occupied by the neuron
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Six Types of Neuroglial Cells two types occur only in the PNS 1) schwann cells wrap repeatedly around nerve fibers in the PNS to produce a myelin sheath similar to the one produced by oligodendrocytes in CNS assist in the regeneration of damaged PNS nerve fibers 2) satellite cells surround the somas in ganglia of the PNS provide electrical insulation around the soma regulate the chemical environment of the neurons
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Myelin myelin sheath – an insulating lipoprotein layer around a nerve fiber myelin sheath insulates a nerve fiber from the ECF formed by oligodendrocytes in CNS and Schwann cells in PNS myelin is the plasma membrane of glial cells 80 % lipid and 20% protein (lipoprotein) myelination – production of the myelin sheath
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Myelin CNS oligodendrocytes myelinate several nerve fibers in their immediate vicinity An oligodendrocyte of the CNS wrapping around the axons of multiple neurons. Here, the myelin spirals inward toward the axon as it is laid down. These contrasting modes of myelination are called centrifugal myelination (“away from the center”) in the PNS and centripetal myelination (“toward the center”) in the CNS anchored to multiple nerve fibers cannot spiral around a nerve fiber like Schwann cells do instead, oligodendrocytes push newer layers of myelin under the older ones myelination spirals inward toward nerve fiber nerve fibers in CNS have no neurilemma or endoneurium protected by bone
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Myelination of a Neuron many Schwann cells or oligodendrocytes are needed to cover one nerve fiber, therefore, the myelin sheath is segmented with nodes of Ranvier and internodes nodes of Ranvier – gaps between the myelin segments internodes – the myelin covered segments between the nodes of Ranvier initial segment – short section of nerve fiber between the axon hillock and the first glial cell trigger zone – the axon hillock and the initial segment combined trigger zone is responsible for initiating a nerve signal
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  • Spring '13
  • ToddPfander
  • myelin sheath, nerve fiber

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