1. Neuronal Function in the Nervous System

2. Learning Objectives 1. Explain parts of a typical nerve cell and describe their functions. 2. Discuss common types of nerve and glia cells. 3. Describe functions of nerve and glia cells. 4. Explain electrical and chemical properties of nerve cells. 5. Describe mechanism of impulse generation and its conduction. 6. Explain nerve cell responses to injuries in the nervous system. 7. Explain differential regenerative processes between central and peripheral nervous system. 8. Discuss common neurotransmitters and their functions.

3. Nerve Cells Basic anatomic and functional unit of the nervous system Primary Function: Two Primary Types

4. Neuron Three Basic Elements General Process

5. Neuron, Myelinated Axon, and Synapse Bhatnagar & Andy, 1995, Figure 5.1.A

6. Nerve Cell Structure of Neurons: Cell Body Two major components 1. Cytoplasm

7. The Cell Body Bhatnagar & Andy, 1995, Figure 5.1.B

8. Nerve Cell Structure of Neurons: Cell Body 2. Nucleus

9. The Cell Body Bhatnagar & Andy, 1995, Figure 5.1.B

10. Nerve Cell Structure of Neurons: Dendritic and Axonal Processes Cytoplasmic extensions Dendrites Nerve fibers

11. Neuron, Myelinated Axon, and Synapse Bhatnagar & Andy, 1995, Figure 5.1.A

12. Nerve Cell Structure of Neurons: Myelin Sheath Speed of nerve conduction is determined by: Myelin

13. Neuron, Myelinated Axon, and Synapse Bhatnagar & Andy, 1995, Figure 5.1.A

14. Nerve Cell Structure of Neurons: Myelin Sheath Myelin

15. Nerve Cell Structure of Neurons: Synapse Connection point between neurons Three Parts: 1. Knob (Synaptic vesicles) 2. Synaptic Cleft 3. Receptive Sites of Connecting Nerve Cells

16. Neuron, Myelinated Axon, and Synapse Bhatnagar & Andy, 1995, Figure 5.1.A

17. Nerve Cell Structure of Neurons: Synapse Process of Nerve Impulses

18. Neuron, Myelinated Axon, and Synapse Bhatnagar & Andy, 1995, Figure 5.1.A

19. Nerve Cell Types Classification: Three Cell Types: 1. Multipolar 2. Bipolar 3. Unipolar

20. Nerve Cell Types Bhatnagar & Andy, 1995, Figure 5.2

21. Neuroglia Cells Function: Location:

22. Neuroglia Cells in the Central Nervous System Four Types of Glia Cells in the CNS 1. Astrocytes Location: Function:

23. Neuroglia Cells in the Central Nervous System 2. Ogliodendroglia 3. Ependymal 4. Microglia

24. Neuroglial Cells in the Peripheral Nervous System Schwann cells Function: Impairments: Demyelinating Neuropathologies Benign Tumors of Schwann Cells

25. Central and Peripheral Nervous Systems Cytological Differences 1. Different myelin forming cells PNS CNS

26. Central and Peripheral Nervous Systems Cytological Differences 2. Presence of endoneurium PNS CNS

27. Nerve Impulse Communication Principles of Process Chemical component Excitability of nerve cells Action potential

28. Nerve Impulse Process Excitability of nerve cells An action potential Activation releasing neurotransmitter Opening of channels in postsynaptic receptors

29. Nerve Impulse Process Resting State Cell is in resting state In this resting state

30. Action Potential: Resting Potential with Polarized Membrane Bhatnagar & Andy, 1995, Figure 5.5A

31. Nerve Impulse Process Resting Membrane Potential Voltage inside the cell membrane Outside the cell membrane Inside the cell membrane Ionic channels

32. Action Potential Bhatnagar & Andy, 1995, Figure 5.5D

33. Membrane Channels Membrane channels are gated Flow of ions through the membrane Depends on: 1. The density of the channels 2. The size of the opening 3. The ion concentration gradient across the membrane

34. Membrane Channels Distribution of sodium and potassium across the cellular membrane Is constantly adjusted by the sodium- potassium pump Because of the membrane pore size

35. Membrane Channels With the attraction of opposite ions and the repulsion of identical ions With this tug of war An electrochemical gradient forms along the membrane

36. Action Potential: Resting Potential with Polarized Membrane Bhatnagar & Andy, 1995, Figure 5.5A

37. Nerve Excitability Excitability Refers to:

38. Nerve Excitability Stimuli can include:

39. Nerve Excitability During the resting state The neuron undergoes several short changes in the intracellular potentials Triggering an action potential

40. Action Potential Bhatnagar & Andy, 1995, Figure 5.5D

41. Action Potential: Generation of Action Potential with Depolarized Membrane Bhatnagar & Andy, 1995, Figure 5.5B

42. Nerve Excitability In membrane depolarization

43. Action Potential Bhatnagar & Andy, 1995, Figure 5.5D

44. Nerve Excitability Membrane potential from this peak returns to the absolute refractive period

45. Action Potential Bhatnagar & Andy, 1995, Figure 5.5D

46. Nerve Excitability Not all stimuli Are strong enough to change the membrane potentials to 10 mV Many weak stimuli with subthreshold strength If temporally and spatially summated Can initiate a nerve impulse Each weak stimulus arrives in a sequence and their cumulative effect is strong enough to initiate an impulse

47. Impulse Conduction Nerve impulse is passively conducted a short distance in the axon

48. Action Potential: Generation of Action Potential with Depolarized Membrane Bhatnagar & Andy, 1995, Figure 5.5B

49. Impulse Conduction This gradually changes the membrane potential in the neighboring area

50. Action Potential: Conduction of Action Potential Along Membrane Bhatnagar & Andy, 1995, Figure 5.5C

51. Impulse Conduction Saltatory Conduction in Myelinated Axons

52. Impulse Conduction Action potential or nerve impulse Excitatory Postsynaptic Potential (EPSP) Inhibitory Postsynaptic Potential (IPSP)

53. Neuronal Responses to Brain Injuries Nerve Cells in the Human Brain Are incapable of further cell division and regeneration Synapses serve as good points of reference for discovering the impact of cellular injuries

54. Neuronal Responses to Brain Injuries Understanding the Processes of Spontaneous Recovery Two Types of Degenerative Changes Occur After Axonal Sectioning 1. Axonal or Retrograde Reaction 2. Wallerian (Anterograde) Degeneration

55. Types of Neuronal Response to Injury Bhatnagar & Andy, 1995, Figure 5.6A

56. Neuronal Response to Injury: Axonal Retrograde Reaction Bhatnagar & Andy, 1995, Figure 5.6B

57. Neuronal Response to Injury: Wallerian Degeneration Bhatnagar & Andy, 1995, Figure 5.6C

58. Axonal Regeneration in Peripheral Nervous System Regeneration of Fibers in the PNS

59. Neuronal Response to Injury: Peripheral Nerve Regeneration Bhatnagar & Andy, 1995, Figure 5.6D

60. Axonal Regeneration in Central Nervous System Axons severed in the CNS

61. Neurotransmitters Along with projections from the reticular formation Regulate brain mechanisms that control: Cognition Language Speech Hearing Brain Tuning Moods Attention Memory Personality Motivation

62. Neurotransmitters Two types of transmitters in the nervous system: 1. Small molecules Include: Acetylcholine Dopamine Norepinephrine Serotonin Glutamate y -aminobutyric acid (GABA) 2. Larger molecules Peptides

63. Neurotransmitters: Acetylcholine Synthesis and Dissolution Acetylcoenzyme A and choline Acetylcholinesterase

64. Neurotransmitters: Acetylcholine in the PNS Location of Cells in PNS: Function: Impairments:

65. Neurotransmitters: Acetylcholine in the CNS Location of Cells In CNS: Function: Impairments:

66. Sites of Cell Bodies and Their Projections in the Brain: Acetylcholine Bhatnagar & Andy, 1995, Figure 5.7A

67. Neurotransmitters: Dopamine Location of Cells: Two Important Dopaminergic Projections 1. Mesostriatal System (Midbrain and Striatum) Pathways: Impairments:

68. Neurotransmitters: Dopamine Two Important Dopaminergic Projections 2. Mesocortical System (Midbrain and Cortical) Pathways: Function: Impairments:

69. Sites of Cell Bodies and Their Projections in the Brain: Dopamine Bhatnagar & Andy, 1995, Figure 5.7B

70. Neurotransmitters: Norepinephrine Location of Cells: Pathways: Ascending Fibers: Descending Fibers Function: Impairments:

71. Sites of Cell Bodies and Their Projections in the Brain: Norepinephrine Bhatnagar & Andy, 1995, Figure 5.7C

72. Neurotransmitters: Serotonin Location of Cells: Pathways: Function: Impairment:

73. Sites of Cell Bodies and Their Projections in the Brain: Serotonin Bhatnagar & Andy, 1995, Figure 5.7D

74. Neurotransmitter: y -Aminobutyric Acid (GABA) Location of Cells: Location of Projections: Function: Impairment:

75. Sites of Cell Bodies and Their Projections in the Brain: GABA Bhatnagar & Andy, 1995, Figure 5.7E

76. Neurotransmitters: Peptides Characteristics: Function:

77. Bhatnagar & Andy Figure 5.7 Abbreviations AmygAmygdala DBDiagonal Band of Broca HABHabenula HypoHypothalamus IPNInterpeduncular Nucleus NNNerves NUCNucleus Nuc. aac.Nucleus Accumbens SubSubstantia ThalThalamus VTAVentral Tegmental Area

78. Define the Following Technical Terms: Action potential Astrocytes Autoimmune Axon Axonal reaction Chromatolysis Cytological Cytoplasm Dendrites Depolarization Endoneurium Excitatory postsynaptic potential Glia cells Hyperplasia Hypertrophy Inhibitory postsynaptic potentials Macrophage Microglia Myelin Nerve cell Neurilemma Nissl bodies Node of Ranvier Oligodendroglia Permeability Phagocyte Polarization Schwann cells Synapse Wallerian degeneration

79. Review Questions 1. With a diagram of a typical nerve cell, identify the major structures and describe their functions. 2. List the major glia cells and describe their functions. 3. Explain how the following terms are related to impulse generation: Action potential Depolarization Membrane excitability Polarized membrane Repolarized membrane Resting potential Subthreshold stimulus Summation

80. Review Questions 4. Describe chemical and electrical events that are related to impulse transmission beginning with resting potentials and ending in generation of action potentials. 5. Describe the effects of inhibitory and excitatory postsynaptic potentials on a postsynaptic neuron. 6. Discuss how nerve and glia cells respond to injuries. Specifically discuss chromatolysis, wallerian degeneration, axonal reaction, and regeneration of axonal fibers.

81. Review Questions 7. Describe how axonal growth in the CNS is different from that in the PNS. 8. Name primary neurotransmitters in the central nervous system and briefly discuss their functions. 9. Describe the pathophysiology of multiple sclerosis and myasthenia gravis.

82. Neuronal Function in the Nervous System Graphics

83. THINGS TO DO BEFORE LECTURE Reticular Formation Cytological