Fundamentals of the Nervous System and Neural Tissue Part A

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