8. Morphology of Typical Motor Neuron 1. nucleus 2. perikaryon 3. cell body 4. axon 5. dendrite 6. Nissl body 7. axon hillock 8. myelin sheath 9. oligodendrocyte 10. Schwann cell 11. skeletal muscle cell 12. neuromuscular junction
9. Neuron Neuronal Function Communication Receptor - Neuron - Effector - Excitability (Irritability) - Conductivity through membrane in intraneuronal conduction via synapse in interneuronal conduction neurotransmitters
10. Neuronal Cell Body (Soma) NUCLEUS Ÿ Chromatin Pattern: Euchromatic euchromatin >>> heterochromatin active mRNA transcription cf. Barr body (facultative heterochromatin) inactive X chromosome in female Ÿ Conspicuous Nucleolus NOR (nucleolar organizing region) active rRNA transcription -- ribosome
11. NB: neuronal cell body NS: Nissl substance NL: nucleolus BB: Barr body
14. Neuronal Cell Body (Soma) Cytoplasmic Organelles Ÿ Nissl substance: rER abundant, parallally arranged rER cisterna active site of protein (polypeptide) synthesis - transport vesicle Ÿ Golgi complex complex of perinuclear Golgi substance glycosylation, sulfation & phosphorylation packing and condensation protein to transport
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17. Camilio Golgi (1843-1926) Golgi apparatus Golgi method (Golgi’s metallic impregnation) Golgi type I & II cell Golgi tendon organ Golgi-Mazzoni corpuscle
18. Neuronal Cell Body (Soma) Protein Synthesizing Assembly Ÿ Euchromatic Nucleus ------- mRNA transcription Ÿ Prominent Nucleolus ------- rRNA (ribosome) synthesis Ÿ Nissl substance: rER ------- polypeptide chain Ÿ Golgi complex ----- destined to transport - no protein synthesizing assembly in axon - neurotransmitters, enzymes, membrane proteins - transport via axonal (axoplasmic) transport
19. Neuronal Cell Body (Soma) Other Cytoplasmic Organelles Ÿ Mitochondria - energy source for ion exchange (Na + -K + exchange pump) and axonal transport Ÿ Lysosome - hydrolytic enzymes --- waste products - lysosomal storage disease (mental retardation, seizure) Pigment Granules Lipofuscin granule , Melanin granule
27. Distinction between Axon and Dendrites Axon Dendrite Dimension number 1 multiple (0, 1, or more) length 200 m – 1 m less than 700 m diameter constant throughout gradually tapered Branching pattern angle almost right angle acute angle site distant from cell body near cell body Structural components Nissl substance absent could be present dendritic spine absent could be present myelin sheath could be associated not associated
34. Distinction between Axon and Dendrites Axon Dendrite Staining property Golgi hard to impregnate well delineated impregnation (except rapid Golgi method) reduced silver more darkly stained less darkly stained Functional direction of efferent afferent conduction (soma -> axon terminal) (dendrite -> soma) exception: pseudounipolar neuron
40. Components of Axonal (Axoplasmic) Transport Components Velocity (mm/day) Transporting Substances Anterograde Axonal Transport Fast Transport 200-400 synaptic vesicle, enzymes neurotransmitters Mitochondrial Transport 50-100 mitochondria Slow Transport Slow Components a (SCa) 0.1 - 1.0 tubulin, neurofilament protein Slow Comnponent b (SCb) 2 - 6 actin, clathrine, calmodulins spectrin, cytoplasmic enzymes Retrograde Axonal Transport 100-200 prelysosomal vesicles, recycled proteins, HRP, WGA neurotrophic viruses Axonal (Axoplasmic) Transport
41. Mechanism of Axonal Transport Fast Anterograde Axonal transport and Retrograde Axonal transport
42. Degeneration and Regeneration of Nervous System 1. Wallerian Degeneration - changes distal to the injury site - myelin breakdown - von B ü ngner’s band - Schwann cell - neuroma formation 2. Axon Reaction (Chromatolysis, Nissl Reaction) - displacement of nucleus - chromatolysis - regenerative processes
51. Nauta method Reduced silver method after axon transection neurofilament transport continues after axon transection Nauta-Gygax method Fink-Heimer method
52. 3 H-labeled amino acid Autoradiography Amino acid is incorporated to protein in neuronal cell bodies Proteins are slowly transported to axonal endings
53. Classification of Neurons (1) by the Number of Processes 1. unipolar neuron 2. pseudounipolar neuron 3. bipolar neuron 4. multipolar neuron (2) by the Length of Axon 1. Golgi type I neuron 2. Golgi type II neuron (3) by the Morphology of Dendrites (Topognostic Value) 1. isodendritic neuron 2. allodendritic neuron 3. idiodendritic neuron
54. 1. unipolar neuron 2. bipolar neuron 3. pseudounipolar neuron 4. multipolar neuron a. axon d. dendrite
55. Pseudounipolar Neuron DRG (dorsal root ganglion) neuron pseudounipolar cell peripheral process central process telodendron cell body in DRG
56. Neuroglia (Neuroglial Cells) Central Neuroglia Astrocyte protoplasmic astrocyte fibrous astrocyte Oligodendrocyte perineuronal satellite cell interfascicular cell Microglia Ependymal Cell Peripheral Neuroglia Schwann Cell in peripheral nerve and ganglion Capsular (Satellite) Cell in ganglion
57. Astrocyte Oligodendrocyte Microglia Central Neuroglia
69. Satellite (Capsular) Cell Squamous Cell encircles neuronal cell body in Ganglion - completely encircles pseudounipolar neuron in spinal and cranial ganglion - neurons of autonomic ganglia were less completely surrounded by satellite cell
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72. Myelin Node of Ranvier - Internodal segment Schmidt-Lantermann’s cleft
77. Giant squid axon 0.5-1 mm in diameter conduction velocity 25 m/s
78. Myelin Conduction velocity is proportional to 1. The Length of Internodal Segment 2. Thickness of Myelin 3. Diameter of Nerve Fiber
79. Conduction velocity of mammalian nerve fiber Group I A 10 - 20 70 -120 Group II A 5 - 12 30 - 70 A γ 3 - 6 15 - 30 Group III A δ 2 - 5 12 - 30 B < 3 3 - 15 Group IV C 0.1 - 1.5 0.5 - 2 Myelinated fiber Unmyelinated fiber
82. MYELIN - Fusion of Plasma Membrane Major Dense Line - fusion of inner leaflet ---- Myelin Basic Protein (MBP) Intraperiod Line - fusion of outer leaflet ---- Proteolipid Protein (PLP) in oligodendrocyte ---- Protein Zero (P 0 ) in Schwann Cell Myelin
83. Myelin 1. trilaminar unit membrane 2. major dense line 3. intraperiod line 4. Cytoplasm of Schwann cell
84. Multiple Slerosis – disease of the myelin Jacqueline Du Pre oligodendrocyte
85. LEPROSY: Mycobactrium leprae infection of Schwann cell Rembrandt. The King Uzziah Stricken with Leprosy.
86. Organization of Nervous System Central Nervous System Gray Matter Nucleus and Cortex White Matter Tracts Peripheral Nervous System Nerve (Peripheral Nerve) Ganglion
90. Peripheral Nerve Endings: Afferent Endings R eceptor Neurons of Craniospinal Ganglion Ÿ pseudounipolar neurons of dorsal root ganglia Ÿ trigeminal (semilunar, Gasserian ganglion), geniculate (VII), superior IX, superior X ganglia (GSA) Ÿ geniculate (VII), inferior IX, inferior X ganglia (VA) Morphological Classification Ÿ free nerve endings Ÿ expanded tip endings Ÿ encapsulated endings ----- CT envestment
91. Afferent Endings Free Nerve Endings - Nerve endings without special structural organization - pain and temperature receptor Expanded Tip Endings - Merkel’s Touch Corpuscle Merkel cells in basal layer of epidermis - Type I Hair cells of Vestibular Labyrinth
94. Merkel’s Touch Corpuscle Ÿ expanded tip ending Ÿ Merkel cell - clear cell located in the basal layer of epidermis - membrane bound electron dense granules resembles synaptic vesicle
