1. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb PowerPoint ® Lecture Slides prepared by Vince Austin, University of Kentucky 11 Fundamentals of the Nervous System and Nervous Tissue Part A

2. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Nervous System  The master controlling and communicating system of the body  Functions  Sensory input – monitoring stimuli occurring inside and outside the body  Integration – interpretation of sensory input  Motor output – response to stimuli by activating effector organs

3. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Nervous System Figure 11.1

4. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Organization of the Nervous System  Central nervous system (CNS)  Brain and spinal cord  Integration and command center  Peripheral nervous system (PNS)  Paired spinal and cranial nerves  Carries messages to and from the spinal cord and brain

5. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Sensory (afferent) division  Sensory afferent fibers – carry impulses from skin, skeletal muscles, and joints to the brain  Visceral afferent fibers – transmit impulses from visceral organs to the brain  Motor (efferent) division  Transmits impulses from the CNS to effector organs Peripheral Nervous System (PNS): Two Functional Divisions

6. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Somatic nervous system  Conscious control of skeletal muscles  Autonomic nervous system (ANS)  Regulates smooth muscle, cardiac muscle, and glands  Divisions – sympathetic and parasympathetic Motor Division: Two Main Parts

7. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The two principal cell types of the nervous system are:  Neurons – excitable cells that transmit electrical signals  Supporting cells – cells that surround and wrap neurons Histology of Nerve Tissue

8. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The supporting cells (neuroglia or glial cells):  Provide a supportive scaffolding for neurons  Segregate and insulate neurons  Guide young neurons to the proper connections  Promote health and growth Supporting Cells: Neuroglia

9. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Most abundant, versatile, and highly branched glial cells  They cling to neurons and their synaptic endings, and cover capillaries  Functionally, they:  Support and brace neurons  Anchor neurons to their nutrient supplies  Guide migration of young neurons  Control the chemical environment Astrocytes

10. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Astrocytes Figure 11.3a

11. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Microglia – small, ovoid cells with spiny processes  Phagocytes that monitor the health of neurons  Ependymal cells – range in shape from squamous to columnar  They line the central cavities of the brain and spinal column.  Main function is to help move the fluid that protects the brain and spinal cord. Microglia and Ependymal Cells

12. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Microglia and Ependymal Cells Figure 11.3b, c

13. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Oligodendrocytes – branched cells that wrap CNS nerve fibers  Schwann cells (neurolemmocytes) – surround fibers of the PNS to protect the axon of a nerve fiber.  Satellite cells surround neuron cell bodies with ganglia Oligodendrocytes, Schwann Cells, and Satellite Cells

14. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 11.3d, e Oligodendrocytes, Schwann Cells, and Satellite Cells

15. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Structural units of the nervous system  Composed of a body, axon, and dendrites  Long-lived, amitotic, and have a high metabolic rate  Their plasma membrane functions in:  Electrical signaling  Cell-to-cell signaling during development Neurons (Nerve Cells)

16. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Neurons (Nerve Cells) Figure 11.4b

17. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Contains the nucleus and a nucleolus  Is the major biosynthetic center  Is the focal point for the outgrowth of neuronal processes  Has no centrioles (hence its amitotic nature)  Contains an axon hillock – cone-shaped area from which axons arise Nerve Cell Body (Perikaryon or Soma)

18. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Processes  Processes are the pojections or growths that come off of a cell body.  The cell body is the focal point for the outgrowth of neuronal processes.  The CNS contains both cell bodies and processes, the PNS contains mostly just processes.  Bundles of nuerons in the CNS are called tracts, in the PNS they are called nerves.

19. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Short, tapering, and diffusely branched processes  They are the receptive, or input, regions of the neuron  Electrical signals are conveyed as graded potentials (not action potentials) Dendrites of Motor Neurons

20. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Slender processes of uniform diameter arising from the hillock  Long axons are called nerve fibers  Usually there is only one unbranched axon per neuron  Rare branches, if present, are called axon collaterals  Axonal terminal – branched terminus of an axon Axons: Structure

21. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Generate and transmit action potentials  Secrete neurotransmitters from the axonal terminals  Movement along axons occurs in two ways  Anterograde — toward axonal terminal  Retrograde — away from axonal terminal Axons: Function

22. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Whitish, fatty (protein-lipoid), segmented sheath around most long axons  It functions to:  Protect the axon  Electrically insulate fibers from one another  Increase the speed of nerve impulse transmission Myelin Sheath

23. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Formed by Schwann cells in the PNS  A Schwann cell:  Envelopes an axon in a trough  Encloses the axon with its plasma membrane  Has concentric layers of membrane that make up the myelin sheath  Neurilemma – remaining nucleus and cytoplasm of a Schwann cell Myelin Sheath and Neurilemma: Formation

24. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Myelin Sheath and Neurilemma: Formation Figure 11.5a-c

25. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Gaps in the myelin sheath between adjacent Schwann cells  They are the sites where axon collaterals can emerge Nodes of Ranvier (Neurofibral Nodes) InterActive Physiology ® : Nervous System I: Anatomy Review PLAY

26. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  A Schwann cell surrounds nerve fibers but coiling does not take place  Schwann cells partially enclose 15 or more axons Unmyelinated Axons

27. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Both myelinated and unmyelinated fibers are present  Myelin sheaths are formed by oligodendrocytes  Nodes of Ranvier are widely spaced  There is no neurilemma Axons of the CNS

28. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  White matter – dense collections of myelinated fibers  Gray matter – mostly soma and unmyelinated fibers Regions of the Brain and Spinal Cord

29. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Structural:  Multipolar — three or more processes  Bipolar — two processes (axon and dendrite)  Unipolar — single, short process Neuron Classification

30. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Functional:  Sensory (afferent) — transmit impulses toward the CNS  Motor (efferent) — carry impulses away from the CNS  Interneurons (association neurons) — shuttle signals through CNS pathways Neuron Classification

31. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Comparison of Structural Classes of Neurons Table 11.1.1

32. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Comparison of Structural Classes of Neurons Table 11.1.2

33. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Comparison of Structural Classes of Neurons Table 11.1.3