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Chapter 8.2: The Nervous System
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Neuroglia Astrocytes Largest and most numerous Maintain blood-brain barrier Isolates CNS from circulation Capillaries impermeable Repair damaged neural tissue
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Figure 8.4
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Neuroglia cont… Oligodendrocytes Coats axons with myelin Nodes of Ranvier Parts of axon with no myelin Internodes Parts of axon with myelin Myelin increases speed of action potential
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Figure 8.5
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Neuroglia cont… Microglia Engulf wastes and pathogens
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Figure 8.4
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Neuroglia cont… Ependymal Cells Produces cerebrospinal fluid
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Figure 8.4
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Neuroglia cont… Satellite Cells Support cell bodies Schwann Cells Covers axons—called neurilemma
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Figure 8.5b
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Demyelination Disorders Demyelination Progressive destruction of myelin Inflammation Axon Damage Scarring of neural tissue Gradual loss of sensation and motor control Numbness and paralysis
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Disorders cont… Multiple Sclerosis (MS) Optic nerve, brain and spinal cord affected Partial loss of vision Problems with speech, balance and motor coordination
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Neuron Anatomy Neuron cell bodies—gray matter Located in ganglia of PNS White matter—bundles of axons Called nerves
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Figure 8.6
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Membrane Potential Polarized—resting cell membrane Resting Potential—membrane potential of resting neuron -70mV More negative ions inside than out of neuron
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Figure 8.8 5
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Potential cont… Depolarization Shift membrane potential towards positive Ex: 0 mV
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Figure 8.8 5
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Potential Cont… Hyperpolarization Shift membrane potential towards more negative Ex: - 80 mV
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Figure 8.8 5
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Potential cont… Action Potential Triggered by depolarization Membrane potential must reach threshold -60 mV
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Figure 8.8 5
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Potential cont… Repolarization Return to resting potential
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Figure 8.8 5
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