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Fundamentals of the Nervous System and Neural Tissue Part A

Fundamentals of the Nervous System and Neural Tissue Part A. 11. Nervous System. Figure 11.1. Divisions of the Nervous System. Efferent (motor) neurons. Afferent (sensory) neurons. Sympathetic. ANS. Somatic. Parasympathetic. Divisions of the Nervous System. CNS. PNS.

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Fundamentals of the Nervous System and Neural Tissue Part A

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  1. Fundamentals of the Nervous System and Neural Tissue Part A 11

  2. Nervous System Figure 11.1

  3. Divisions of the Nervous System

  4. Efferent (motor) neurons Afferent (sensory) neurons Sympathetic ANS Somatic Parasympathetic Divisions of the Nervous System CNS PNS

  5. Neuroglia – Supporting Cells • Provide scaffolding for neurons • Segregate & insulate neurons • Guide growing neurons to proper connections • Promote health & growth of neurons • Cell types • Astrocytes • Microglial cells • Ependymal cells • Oligodentrocytes • Schwann cells • Satellite cells

  6. Astrocytes • Abundant, versatile, and highly branched CNS cell • Cover capillaries • Support & brace neurons • Anchor neurons to their nutrient supplies • Guide migration of young neurons • Control the chemical environment

  7. Microglial Cells • Microglia – small, ovoid cells with spiny processes • Phagocytic • Monitor health of neurons

  8. Ependymal Cells • Squamous or columnar cells lining ventricles of brain and spinal cord

  9. Oligodendrocytes • Branched cells that wrap CNS nerve fibers (axons)

  10. Schwann Cells and Satellite Cells • Schwann cells surround axons of PNS neurons • Satellite cells surround bipolar neuron cell bodies in ganglia

  11. Myelin Sheath and Neurilemma Formation • Whitish, fatty (protein-lipid), segmented sheath around most long axons sphingomyelin • Formed by: • Schwann cells in the PNS • Oligodendrocytes in CNS • Functions to: • Protect axons • Electrically insulate fibers • Increases speed of impulse transmission

  12. Myelin Sheath and Neurilemma Formation • A Schwann cell: • Encloses the axon with its plasma membrane • Concentric layers of membrane make up the myelin sheath • Neurilemma • Nucleus and cytoplasm of a Schwann cell

  13. Neurons (Nerve Cells) • Functional units of neurons • Composed of a body, axon, and dendrites • Long-lived, amitotic, and have a high metabolic rate • Plasma membrane functions in: • Electrical signaling • Cell-to-cell signaling during development

  14. Axon Function • Generate and transmit action potentials • Secrete neurotransmitters from termini • Intracellular movement along axons • Anterograde — toward terminus • Retrograde — away from terminus, toward soma

  15. Axons of the CNS • Both myelinated and unmyelinated fibers are present • Myelin sheaths are formed by oligodendrocytes • Nodes of Ranvier are widely spaced • There is no neurilemma

  16. Regions of the Brain and Spinal Cord • White matter – dense collections of myelinated fibers • Gray matter – mostly soma and unmyelinated fibers

  17. Neuron Classification • Structural: • Multipolar - three or more processes • Bipolar - two processes (axon and dendrite) • Unipolar - single process diverges into 2 conductive regions • Functional: • Sensory (afferent) — transmit impulses toward the CNS • Motor (efferent) — carry impulses away from the CNS • Interneurons (association neurons) — shuttle signals through CNS pathways

  18. Structural Classes of Neurons

  19. Structural Classes of Neurons

  20. Structural Classes of Neurons

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