THE NERVOUS SYSTEM NEURAL TISSUE Cells in Nervous Tissue...

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THE NERVOUS SYSTEM: NEURAL TISSUE
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Neurons Neuroglia Cells in Nervous Tissue
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about half the volume of cells in the CNS smaller than neurons 5 to 50 times more numerous do NOT generate electrical impulses divide by mitosis 2 types in PNS Schwann cells Satellite cells 4 types in the CNS Astrocytes Oligodendrocytes Microglia Ependymal cells Neuroglia (Glia)
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Largest of glial cells Star shaped with many processes projecting from the cell body Help form and maintain blood-brain barrier Provide structural support for neurons Regulate the chemical/ion environment for generation of nerve impulse Regulate nutrient & ion concentrations for neuron survival Take up excess neurotransmitters Astrocyte places itself in.. Regulate levels (concentrations) Of neurotransmitters Protect neuoron Astrocytes (star cells)
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Oligodendrocytes Most common glial cell type Each forms myelin sheath around the axons of neurons in CNS Analogous to Schwann cells of PNS Form a supportive network around CNS neurons
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Microglia Small cells found near blood vessels Phagocytic role - clear away dead cells protect CNS from disease through phagocytosis of microbes migrate to areas of injury where they clear away debris of injured cells - may also kill healthy cells Ability to eat, clear away dead cells & sometimes living cells few processes derived from mesodermal cells that also give rise to monocytes and macrophages
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Ependymal Cells line ventricles of the brain & central canal of spinal cord produce & circulate the cerebrospinal fluid (CSF) CSF = colorless liquid that protects the brain and SC against chemical & physical injuries, carries oxygen, glucose and other necessary chemicals from the blood to neurons and neuroglia Filters & creates CSF “blood of nervous tissue” epithelial cells arranged in a single layer range in shape from cuboidal to columnar
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Cells of the CNS
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Flat cells surrounding PNS neuronal bodies hold the cell bodies together to form a ganglion PNS: Satellite Cells
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PNS: Schwann Cells produces part of the myelin sheath surrounding an axon in the PNS contributes regeneration of PNS axons Neurilemma – outermost layer***
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Cells of the PNS In PNS, cells can regrow Each blue correspond with schwann cell & myelin sheath Gaps between blue = nodes of ranvier
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Neurons have the property of electrical excitability - ability to produce action potentials or nerve impulses in response to stimuli Muscles also generate action potentials, although different
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Representative Neuron 1. cell body or soma
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