Cells can divide rapid mitosis in tumor formation

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Cells can divide rapid mitosis in tumor formation (gliomas) 4 cell types in CNS astrocytes, oligodendrocytes, microglia & ependymal 2 cell types in PNS schwann and satellite cells Neuroglial Cells
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Astrocytes Star-shaped cells Form blood-brain barrier by covering blood capillaries Provide structural support Most common glial cell type
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Oligodendrocytes – OL-i-go-den-dro-sit Each forms myelin sheath around more than one axon in CNS Analogous to Schwann cells of PNS
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Microglia Small cells found near blood vessels Phagocytic role - clear away dead cells
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Ependymal cells – ep-EN-de-mal Form epithelial membrane lining cerebral cavities & central canal Produce cerebrospinal fluid (CSF)
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Satellite Cells Flat cells surrounding neuronal cell bodies in peripheral ganglia Support neurons in the PNS ganglia
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Schwann Cell Cells encircling PNS axons Each cell produces part of the myelin sheath surrounding an axon in the PNS
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Axon Coverings in PNS All axons surrounded by a lipid & protein covering (myelin sheath) produced by Schwann cells gaps called nodes of Ranvier Myelinated fibers appear white jelly-roll like wrappings made of lipoprotein = myelin acts as electrical insulator speeds conduction of nerve impulses Unmyelinated fibers slow, small diameter fibers only surrounded by neurilemma but no myelin sheath wrapping
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Myelination in PNS Schwann cells myelinate (wrap around) axons in the PNS during fetal development Tube guides growing axons that are repairing themselves
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Myelination in the CNS Oligodendrocytes myelinate axons in the CNS No neurolemma is formed Little regrowth after injury is possible due to the lack of a distinct tube or neurilemma
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Gray and White Matter White matter = myelinated processes (white in color) Gray matter = nerve cell bodies, dendrites, axon terminals, bundles of unmyelinated axons and neuroglia (gray color) In the spinal cord = gray matter forms an H-shaped inner core surrounded by white matter In the brain = a thin outer shell of gray matter covers the surface & is found in clusters called nuclei inside the CNS
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Electrical Signals in Neurons Neurons are electrically excitable due to the voltage difference across their membrane Communicate with 2 types of electric signals action potentials that can travel long distances graded potentials that are local membrane changes only In living cells, a flow of ions occurs through ion channels in the cell membrane
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Structure of Atoms Units of matter of all chemical elements are called atoms . An element is a quantity of matter composed of atoms of the same type. Atoms contain: Nucleus: protons (p+) & neutrons (neutral charge) Electrons (e-) surround the nucleus as a cloud (electron shells are designated regions of the cloud)
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Ions, Molecules, & Compounds Ions an atom that gave up or gained an electron written with its chemical symbol and (+) or (-) Molecule atoms share electrons written as molecular formula showing the number of atoms of each element (H2O)
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