Cells of the Nervous System
18 Cards in this Set
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Neurons
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- conduct electrical impulses in the nervous system
-carry information in the form of action potentials over long distances
-amitotic; division of cell nucleus w/o mitotic apparatus
**once mature never divide again
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Neuron structure
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-input region; receptive or dendritic region
-conducting region; carry action potentials (long distance communication part of the cell)
-secretory/output region; neurotransmitter is released
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Dendrite
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-input region
-NEVER myelinated
-DO NOT conduct action potentials; instead they conduct potentials that are graded
-graded potentials --> toward neuronal cell body
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Cell body
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-protein factor of the neuron
-contains nucleus
-most of the protein synthesis in the neuron occurs in the cell body
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Nissl substance
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-characteristic of neurons and is an elaborated form of rough endoplasmic reticulum
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Axon/conducting region
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-extends from cell body
-end of action potential; axons branch extensively to innervate other neurons, muscle fibers, or glands (telodendria)
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Action potentials
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-all or none electrical signals that provide rapid communication in neurons over long distance
**trigger zone is the site of action potential initiation
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Telodendria
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forms the axon terminals
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Axon terminals
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-secretory regions of the neuron; form the presynaptic portions of the neuron which release neurotransmitter onto the postsynaptic cell
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Sensory neurons (afferent)
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-Found in both peripheral and CNS
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Motor neurons (efferent)
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-Can be found in both peripheral and CNS
-carry information toward the effector organs
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Associative (interneurons)
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-confined to CNS
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3 types of glial cells in CNS
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**All neuronal and glial cells originated embryologically as neuroectodermal cells; except for microglial cells
1. Astrocytes, cells with many processes giving them a star-like appearance
2. Oligodendrocytes, cells with few (oligo) branches (dendro)
3. Microglial cells;
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Ependymal cells
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**supporting cells in CNS, not usually glial cells
-form an epithelium that lines the ventricles of the brain
-responsible for moving the cerebrospinal fluid with beating cilia
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Astrocytes
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-regulates the concentration of ions, particularly K+ by pumping ions
-regulates the concentration of neurotransmitters in the extracellular space since neuronal activity can also lead to increases in the extracellular concentration of neurotransmitters
- wrapped around capillaries;…
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Extracellular space
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-space between the cells
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Oligodendrocytes
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-in CNS
-responsible for forming the myelin sheaths around axons; Myelin forms the insulating layers around neurons so that the action potentials can conduct more rapidly
-responsible for forming the white matter in the CNS
-can envelope several axons and wrap them with myelin
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Myelination
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-proceeds when processes of oliogodendrocytes wraps around the axon forming layer upon concentric layer of myelin
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Muscle System