Chapter 12: Fundamentals of theNervous System and Nervous Tissue Overview of the NS     PNS (Peripheral Nervous System)  ...
Functional Overview of NS                     PNSCNS = Brain and                     1. Sensory or afferent division Spina...
Made up of neuronsand neuroglia
Similar to fig 12.3
Cellular Organization of Neural TissueTwo cell types:1. Neurons  1.   “Excitable” cells2. Neuroglia (mostly not excitable)...
1. Typical Neuron Structure Cell body or Soma with Perikaryon Dendrites Axon with axon hillock Synaptic terminals         ...
Cell body = Soma
The “signal,” or ActionPotential is carriedalong the neurilemmaFaster if axon ismyelinated
Nerve structure•A nerve is USUALLY both sensoryand motor (axons transmit only in onedirection).    •Some significant excep...
Synapse Site of communication between two nerve cells or nerve cell and effector cell     Presynaptic and postsynaptic   ...
Chemical Synapse vs. Electrical SynapseSpace between two cellsSignal transduction via a  neurotransmitter, usually AChMost...
Chem.SynapseStructure 1.   Axon terminal of presynaptic cell, with vesicles of      neurotransmitter(NT) 2.   Synaptic cle...
Color enhancedTEMx 186,480
Structural Neuron ClassificationAnaxonic  In CNS and Sense OrgansUnipolar  Also called pseudounipolar  Sensory neurons    ...
Structural Neuron Classification cont. . .Bipolar  Unmyelinated  Rare, but important in    special sensesMultipolar  Most ...
Functional Neuron Classification                         1)      Sensory (Afferent)                              1)   Soma...
Neuron OrganizationDivergence - One neuron synapses with several, effectively"spreading the word".Convergence - Several ne...
2. Neuroglia (glue)AKA Glial Cells10-50 X more glial cells than neuronsSupporting Cells Structural and nutritionalEnhance ...
2. Neuroglia (glue), cont’d In the CNS:             In the PNS:     Astrocytes             Satellite Cells     Microgli...
Astrocytes: largest & most numerous  BBB,  control of environment  structural framework & repairs  regulation of ions,and ...
Microglial cellsSmallestPhagocytosis  # during infection orinjuryDerived from white bloodcells
Ependymal cellsLining of ventricles & central canalSome regions ciliatedSome specialized to produce and monitor   CSF
OligodendrocytesSmaller than astrocyteCover neurons with myelin in CNS (white matter vs.  gray matter!)  Myelin improves t...
The Myelin Sheath              p 357 The lipoprotein “myelin” is wrapped around and around   the axon in “myelinated nerve...
Schwann Cells: AKA neurolemmocytes                     Surround all peripheral axons!                     Responsible for ...
Schwann Cells (in the PNS)                                Nonmyelinated Myelinated                 Refer to Fig           ...
Demyelination Multiple sclerosis (p 365)       Guillain-Barré Syndrome     Autoimmune destruction of      Autoimmune des...
Some TerminologyCollections of cell bodies –  ganglion in PNS  nucleus in CNSBundles of axons (or fibers) –  tracts in CNS...
The circuit fig 12.9
Chapter12 neuraltissuemarieb
Chapter12 neuraltissuemarieb
Chapter12 neuraltissuemarieb
Chapter12 neuraltissuemarieb
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Chapter12 neuraltissuemarieb

  1. 1. Chapter 12: Fundamentals of theNervous System and Nervous Tissue Overview of the NS  PNS (Peripheral Nervous System)  CNS (Central Nervous System) Neurons Neuroglia Synapse Some nomenclature Developed by John Gallagher, MS, DVM
  2. 2. Functional Overview of NS PNSCNS = Brain and 1. Sensory or afferent division Spinal Cord with sensory neurons. Integration, Brings sensory info from processing and PNS to CNS. coordination of Begins at receptors sensory data and motor commands 2. Motor or efferent division with motor neurons. Higher functions Brings motor commands to peripheral tissue. Ends at effector cells.
  3. 3. Made up of neuronsand neuroglia
  4. 4. Similar to fig 12.3
  5. 5. Cellular Organization of Neural TissueTwo cell types:1. Neurons 1. “Excitable” cells2. Neuroglia (mostly not excitable)  Schwann cells  Satellite cells  Astrocytes  Oligodendrocytes  Microglial cells  Ependymal cells
  6. 6. 1. Typical Neuron Structure Cell body or Soma with Perikaryon Dendrites Axon with axon hillock Synaptic terminals Fig 12.4
  7. 7. Cell body = Soma
  8. 8. The “signal,” or ActionPotential is carriedalong the neurilemmaFaster if axon ismyelinated
  9. 9. Nerve structure•A nerve is USUALLY both sensoryand motor (axons transmit only in onedirection). •Some significant exceptions in cranial nerves•Similar to muscle terminology •Epineurium •Covers the nerve •Perineurium •Covers a fascicle •Endoneurium •Covers an axon Fig 12.16, p 333
  10. 10. Synapse Site of communication between two nerve cells or nerve cell and effector cell  Presynaptic and postsynaptic neurons neuro-effector junctions, e.g., Motor End Plate Electrical vs. chemical synapses
  11. 11. Chemical Synapse vs. Electrical SynapseSpace between two cellsSignal transduction via a neurotransmitter, usually AChMost common Direct physical contact between cells = gap junctions Direct signal transduction Rare, but occurs in CNS and HEART
  12. 12. Chem.SynapseStructure 1. Axon terminal of presynaptic cell, with vesicles of neurotransmitter(NT) 2. Synaptic cleft 3. Dendrite or cell body of postsynaptic cell 4. Unidirectional
  13. 13. Color enhancedTEMx 186,480
  14. 14. Structural Neuron ClassificationAnaxonic In CNS and Sense OrgansUnipolar Also called pseudounipolar Sensory neurons See fig. 12.2
  15. 15. Structural Neuron Classification cont. . .Bipolar Unmyelinated Rare, but important in special sensesMultipolar Most common All motor neurons
  16. 16. Functional Neuron Classification 1) Sensory (Afferent) 1) Somatic 2) Visceral 2) Motor (Efferent) 1) Somatic 2) Visceral 3) Interneurons
  17. 17. Neuron OrganizationDivergence - One neuron synapses with several, effectively"spreading the word".Convergence - Several neurons synapse with a single neuron,concentrating the input.Serial processing - step-wise, sequentialParallel processing - simultaneous processing of differentinformation
  18. 18. 2. Neuroglia (glue)AKA Glial Cells10-50 X more glial cells than neuronsSupporting Cells Structural and nutritionalEnhance conduction  Schwann cells (neurolemmocytes)Ability to divide  Think about tumors (malignant glioma)  New Information: Some glial cells are excitable
  19. 19. 2. Neuroglia (glue), cont’d In the CNS: In the PNS:  Astrocytes  Satellite Cells  Microglia  Schwann Cells  Ependymal Cells  Oligodendrocytes
  20. 20. Astrocytes: largest & most numerous BBB, control of environment structural framework & repairs regulation of ions,and nutrients, gases
  21. 21. Microglial cellsSmallestPhagocytosis  # during infection orinjuryDerived from white bloodcells
  22. 22. Ependymal cellsLining of ventricles & central canalSome regions ciliatedSome specialized to produce and monitor CSF
  23. 23. OligodendrocytesSmaller than astrocyteCover neurons with myelin in CNS (white matter vs. gray matter!) Myelin improves the rate of impulse conduction
  24. 24. The Myelin Sheath p 357 The lipoprotein “myelin” is wrapped around and around the axon in “myelinated nerves.” Node of Ranvier = gap between neurolemmocytesIn CNS:  Called oligodendrocytesIn PNS:  Called neurolemmocytes or Schwann Cells
  25. 25. Schwann Cells: AKA neurolemmocytes Surround all peripheral axons! Responsible for myelination of PNS Involved in repair mechanism after injury Wallerian Degeneration myelinated
  26. 26. Schwann Cells (in the PNS) Nonmyelinated Myelinated Refer to Fig 12.7
  27. 27. Demyelination Multiple sclerosis (p 365) Guillain-Barré Syndrome  Autoimmune destruction of  Autoimmune destruction of myelin sheath in the CNS myelin sheath in the PNS  Young adult women  Usually a consequence of  Usually idiopathic an infectious disease  Genetic?  Leg weakness
  28. 28. Some TerminologyCollections of cell bodies – ganglion in PNS nucleus in CNSBundles of axons (or fibers) – tracts in CNS nerves in PNS“White matter” = myelinated axons, both nerves and tracts“Gray matter” = non-myelinated material, dendrites, synapses and cell bodies as well as nonmyelinated axons. In CNS – nucleus; in PNS - ganglia
  29. 29. The circuit fig 12.9

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