Nervous System Fall 2007

Nervous System Fall 2007 - NERVOUS SYSTEM Nervous System...

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NERVOUS SYSTEM
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Nervous System Figure 11.1
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Divisions of the Nervous System Central Nervous System (CNS) Brain Spinal Cord Peripheral Nervous System (PNS) Cranial Nerves (nerves = collection of axons): nerves connected to brain Spinal Nerves: nerves connected to spinal cord Ganglia (collection of nerve cell soma (cell body) outside the brain or spinal cord)
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Structure of a Neuron Figure 11.4b
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Neuronal Components Dendrites: Receive information from other neurons or the external environment about specific conditions present at that time Soma: Contains organelles necessary for cell survival; Contains the axon hillock (the integration portion of the neuron) that leads into the axon Axon: Transmits information to other neurons, muscles or glands
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Axons and Myelin Sheaths Myelin Sheath: Axons may be surrounded by a sheath comprised of lipids and proteins There are gaps within the myelin sheath that are called Nodes of Ranvier (axon collaterals may occur at these nodes) Oligodendrocytes form the myelin sheath for cells in the CNS Schwann Cells form the myelin sheath for cells in the PNS
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Myelin Sheath and Neurilemma: Formation Figure 11.5a-c
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Figure 11.3d, e Oligodendrocytes, Schwann Cells, and Satellite Cells
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Unmyelinated Axons Occur in both the CNS and PNS In the PNS: Schwann cells still surround the axons but no coiling takes place and the Schwann cells can surround multiple axons
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Saltatory Conduction Figure 11.16
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Nerve Fiber Classification Based on Myelination, Axon Diameter, Speed of Conduction: Type A fibers: Largest diameter-4 to 20 micrometers; fastest conduction-140 meters per second; myelinated Type B fibers: Diameter of 2 to 4 micrometers; conduction speed of 18 meters per second; usually myelinated Type C fibers: Diameter of less than 2 micrometers; conduction speed of 1 meter per second; unmyelinated
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Multiple Sclerosis (MS) An autoimmune disease Affects primarily young adults Nerve fibers sever and the myelin sheath becomes a scleroses (no longer able to function) Symptoms: lack of muscle control, weakness, visual disturbances Short-circuiting of nerve impulses
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Structural Classification of Neurons Based on the number of processes that extend from the soma Types: Multipolar: three or more processes that extend from the soma Bipolar: one axon and one dendrite (2 processes) that extend from the soma Unipolar: one short process that extends from the soma
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Comparison of Structural Classes of Neurons Table 11.1.2
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Neuronal Synapses Synapses are spaces between a neuron and another neuron, a muscle, or a gland Terminology: Pre-synaptic neuron: neuron that is bringing impulses (electrical signals) toward the synapse Post-synaptic cell: cell that transmits impulses away from the synapse Most Synapses are Chemical A Molecule is Released into the Synapse and Signals the Post-Synaptic Cell
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Types of Synapses Most common types:
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This note was uploaded on 04/15/2008 for the course BIOL 310 taught by Professor Kay-nishiyama during the Fall '07 term at CSU Northridge.

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Nervous System Fall 2007 - NERVOUS SYSTEM Nervous System...

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