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Chapter 8.2: The Nervous System

Chapter 8.2: The Nervous System. Neuroglia. Astrocytes Largest and most numerous Maintain blood-brain barrier Isolates CNS from circulation Capillaries impermeable Repair damaged neural tissue. Figure 8.4. Neuroglia cont…. Oligodendrocytes Coats axons with myelin Nodes of Ranvier

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Chapter 8.2: The Nervous System

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  1. Chapter 8.2: The Nervous System

  2. Neuroglia • Astrocytes • Largest and most numerous • Maintain blood-brain barrier • Isolates CNS from circulation • Capillaries impermeable • Repair damaged neural tissue

  3. Figure 8.4

  4. 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

  5. Figure 8.5

  6. Neuroglia cont… • Microglia • Engulf wastes and pathogens

  7. Figure 8.4

  8. Neuroglia cont… • Ependymal Cells • Produces cerebrospinal fluid

  9. Figure 8.4

  10. Neuroglia cont… • Satellite Cells • Support cell bodies • Schwann Cells • Covers axons—called neurilemma

  11. Figure 8.5b

  12. Demyelination Disorders • Demyelination • Progressive destruction of myelin • Inflammation • Axon Damage • Scarring of neural tissue • Gradual loss of sensation and motor control • Numbness and paralysis

  13. Disorders cont… • Multiple Sclerosis (MS) • Optic nerve, brain and spinal cord affected • Partial loss of vision • Problems with speech, balance and motor coordination

  14. Neuron Anatomy • Neuron cell bodies—gray matter • Located in ganglia of PNS • White matter—bundles of axons • Called nerves

  15. Figure 8.6

  16. Membrane Potential • Polarized—resting cell membrane • Resting Potential—membrane potential of resting neuron • -70mV • More negative ions inside than out of neuron

  17. Figure 8.8 5

  18. Potential cont… • Depolarization • Shift membrane potential towards positive • Ex: 0 mV

  19. Figure 8.8 5

  20. Potential Cont… • Hyperpolarization • Shift membrane potential towards more negative • Ex: - 80 mV

  21. Figure 8.8 5

  22. Potential cont… • Action Potential • Triggered by depolarization • Membrane potential must reach threshold • -60 mV

  23. Figure 8.8 5

  24. Potential cont… • Repolarization • Return to resting potential

  25. Figure 8.8 5

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