1. Nervous System Notes Part 3

2. EVEN MORE INTERESTING NERVOUS SYSTEM FACTS The human brain alone consists of about 100 billion neurons. If all these neurons were to be lined up, it would form a 600 mile long line. At any given point in time, only four percent of the cells in the brain are active, the rest are kept in reserve.

3. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Neurons Figure 7.4

4. NOTES – CELLS OF THE NERVOUS SYSTEM NEURONS 3 basic parts 1. Cell Body 1 nucleus 2. Dendrites carry information TOWARD the cell body

5. 3. Axon carries information AWAY from the cell body many neurons are surrounded by a MYELIN SHEATH fatty tissue that speeds up the nerve impulse

6. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Classification Figure 7.6

7. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.8a Structural Classification of Neurons  Multipolar neurons—many extensions from the cell body

8. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structural Classification of Neurons  Bipolar neurons—one axon and one dendrite Figure 7.8b

9. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structural Classification of Neurons  Unipolar neurons—have a short single process leaving the cell body Figure 7.8c

10. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Support Cells  Support cells in the CNS are grouped together as “neuroglia”  Function: to support, insulate, and protect neurons

11. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Support Cells  Astrocytes  Abundant, star-shaped cells  Brace neurons  Form barrier between capillaries and neurons  Control the chemical environment of the brain

12. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Support Cells Figure 7.3a

13. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Support Cells  Microglia  Spiderlike phagocytes  Dispose of debris

14. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Support Cells Figure 7.3b

15. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Support Cells  Ependymal cells  Line cavities of the brain and spinal cord  Circulate cerebrospinal fluid

16. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Support Cells Figure 7.3c

17. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Support Cells  Oligodendrocytes  Wrap around nerve fibers in the central nervous system  Produce myelin sheaths

18. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Support Cells Figure 7.3d

19. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Support Cells  Satellite cells  Protect neuron cell bodies  Schwann cells  Form myelin sheath in the peripheral nervous system

20. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Support Cells Figure 7.3e

21. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Protection of the Central Nervous System  Scalp and skin  Skull and vertebral column  Meninges  Cerebrospinal fluid (CSF)  Blood-brain barrier

22. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Protection of the Central Nervous System Figure 7.17a

23. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Meninges  Dura mater  Double-layered external covering  Periosteum—attached to inner surface of the skull  Meningeal layer—outer covering of the brain  Folds inward in several areas

24. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Meninges  Arachnoid layer  Middle layer  Web-like  Pia mater  Internal layer  Clings to the surface of the brain

25. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Meninges Figure 7.17b

26. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cerebrospinal Fluid (CSF)  Similar to blood plasma composition  Formed by the choroid plexus  Forms a watery cushion to protect the brain  Circulated in arachnoid space, ventricles, and central canal of the spinal cord

27. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.18a–b Ventricles and Location of the Cerebrospinal Fluid

28. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ventricles and Location of the Cerebrospinal Fluid Figure 7.18c