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					Histology SSN                                                                 October 26, 2004



NERVE
                                                              So Young Kim, sk2298
                                                              Missy Walker, maw2106



The Basics (fill in with presentation)




Nervous System Classifications (specific to this Histo lab)

                                     Nervous System


                Central NS                                    Peripheral NS


Spinal Cord     Cerebellum    Cerebral Cx            ANS          Somatic Enteric (GI)
                                                  (Ganglia) (Peripheral Nerve)



                              (Parasympathetic)      (Sympathetic)




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   Histology SSN                                                                               October 26, 2004


   Functions & Histological Features
                CNS                                                             PNS
                Spinal Cord Cerebellum                      Cerebral Cx         ANS                Peripheral
                                                                                Ganglion           Nerve
Distinguishing *Butterfly              *Purkinje            *Pyramidal          *Site of           *Nerve
Feature          = gray matter         Cells                Cells               neuronal cell      bundles
                    -- dorsal horn –   -    eosinophilic     -- specialized     bodies             -- look for
                   narrow, sensory          pear-flask      motor cortex;       - large, round     axons in cross-
                   -- ventral horn –        shaped;         distinctive         cells; prominent   section (round,
                   wider, motor             UNIQUE          shape, scattered.   nucleoli;          clear/ white
                                       -    dendrites      --very big clear    wreathed in        bodies
                                            mlcr layer      (euchromatic)       satellite cells    (myelin) with
                                       -    f(n):           nucleus with                           central “dot”)
                                            outflow of      dark nucleolus
                                            cerebellum
Functions          Transmits           Motor                Higher              Sympathetic        Somatic
(general;          signals to &        coordination         processing          & Para-            motor &
simplified)        from brain;                                                  sympathetic        sensory
                   site of reflex                                               Note: slide
                   control                                                      19&20 are of
                                                                                sympathetic
                                                                                ganglia
White Matter       *exterior,          *most interior       *interior           N/A                N/A
(axons)            axons               layer – looks
                   traveling to        diffuse, w/in
                   & from brain        granular layer
                    - axons cut in     (don‟t confuse w/
                   cross section in    outer, molecular
                   spinal cord         layer of gray
                   preparation         matter (see
                                       below))
Gray Matter        *butterfly       *molecular +            *exterior           N/A                N/A
(cell bodies)        - processes    granular
                   from cell bodies layers
                   usually exit        - molecular layer
                   gray matter in          = outermost,
                   plane of section        pale staining,
                                           mostly axons
                                           & dendrites
                                       - granular layer
                                           = cellular,
                                           basophilic
                                       - Purkinje cells
                                           separate the
                                           two




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Histology SSN                                                                              October 26, 2004


Extraneuronal Cells
Function                                 Cells in CNS                           Cells in PNS
         Support                   Astroglia                          Satellite Cells
                                   - “star-shaped”                    -    cuboidal cells, surround cell
                                   - structural support                    bodies IN AUTONOMIC
                                   extend processes to wrap                GANGLIA
                                   around capillaries  form          -    Do Not Make Myelin
                                   BBB
    Myelin Production              Oligodendrocytes                   Schwann Cells
                                   -produce & maintain myelin         - form myelin sheath that
                                   sheath in CNS                           insulates axons
    Connective Tissue              None – NO Collagen                 Fibroblasts



Neuronal Supporting Structures
Function                             CNS                                             PNS
Supporting/Surrounding     Meninges:                                      For Peripheral Nerve
Tissues:                                                                  Bundles Only:
               Innermost Pia Mater – thin, direct contact                 Endoneurium – Vascular,
                                   with brain & SC                        arround individual nerve fibers
                       Middle      Arachnoid –“spider-web”;               Perineurium – Arranges axons
                                   sends delicate trabeculae to pia       into „fascicles‟
                                   (subarachnoid space is filled w/
                                   CSF)
                   Outermost       Dura Mater – “hard”; durable           Epineurium – binds „fascicles‟
                                   outer covering                         into „bundles‟


                Figure: Schematic of connective tissue layers in peripheral nerve
                bundle.


                                                                                             Epineurium
                                                                                             binds fascicles 
                                                                                             bundles



            Fascicle



                                                                                                Perineurium
                                                                                                binds nerves 
                                                                                                fascicles
Endoneurium
wraps individual
neurons                              Peripheral Nerve Bundle




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Histology SSN                                                                  October 26, 2004


High-Yield Tips:

   Peripheral Nerve vs. Smooth Muscle:
-   nerve tissue more compact and less eosinophilic
-   ***nerve tissue wavy & bubbly – arises from myelin leaking out upon staining

   Dendrites vs. Axons:
-   with Nissl staining, if see process that stains dark blue, dendrite, not axon. . . axons
    contain no synthetic machinery and therefore do not stain w/ Nissl

   Molecular Layer of Cerebellum vs. White Matter of Cerebellum (cerebellar
    medulla)
-   Look for Purkinje cells. Purkinje cells are very distinct, and they demarcate the
    border b/t molecular & granular layers of the cerebellum. The white matter of the
    cerebellum resides underneath the basophilic granular layer.

   Mnemonic: “Satellites are on the periphery of space.”
-   In other words, satellite cells are found in the peripheral nervous system.

   Mnemonic: “Pyramidal cells are in the Cerebral Cortex.”




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Histology SSN                                                                     October 26, 2004



NERVE QUESTIONS
Questions 1-2 pertain to the structures at the pointers in Figures A and B.

1. Which of the following statements is correct regarding the cells at the pointers in Figures A
and B?
       a. The cells are situated in white matter.
       b. The cells are situated in a ganglion.
       c. The cells are situated in the gray matter.
       d. The cells are situated between the white and gray matter.

2. In Figure B the processes at the arrow are:
        a. myelinated fibers.
        b. axons.
        c. collagen fibers.
        d. dendrites

Question 3:
3. Which figure(s) demonstrates smooth muscle?
       a. Figure A
       b. Figure B
       c. both Figures A and B
       d. neither

Question 4:
4. The region at the pointer is required for: (choose all that apply)
        a. protein synthesis.
        b salutatory conduction.
        c. insulation.
        d. production of endoneurium.

Question 5:
5. All of the following characterize the organ depicted by the slide except:
        a. Microglia
        b. Myelinated axons
        c. Fibroblasts
        d. Oligodendrocytes

Question 6:
6. Which of the following is TRUE of the cell at the pointer?:
       a. maintains stable microenvironment
       b. resides in spinal cord.
       c. is producing myelin.
       d. transmits signals from molecular to granular layers.




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Histology SSN                                                                October 26, 2004



NERVE ANSWERS

1. C. Cerebellum, Pointer A on Purkinje cell, Pointer B on Purkinje cell dendrite. This is
a Purkinje cell in the cerebellum, found at the junction between the molecular and
granular layers. The cell body lies in the granular layer. Its dendrites branch out in the
molecular layer.

2. D. The arrow points to the dendrites of the Purkinje cell in the molecular layer.

3. B. Figure A, peripheral nerve; Figure B, smooth musc. Peripheral nerve and smooth
muscle are hard to tell apart. Here are some distinctions:
       -nerve tissue tends to be more compact, less eosinophilic, wavy and bubbly
       because there are regions where myelin has leaked out.
       -smooth muscle is more diffuse, more intense eosinophilic color.

4. B & C. Peripheral nerve, pointer on myelin sheath. The myelin sheath is layers of
lipid wrapping around the axon. It is required for saltatory conduction. It is also used for
insulation.

5. C. Figure depicts cerebral cortex. There are different support cells in the CNS and
PNS. This is a section from the CNS. There are fibroblasts in the PNS but not the CNS.

6. A. This is a satellite cell, found in autonomic ganglia. These PNS support cells do not
make myelin, while Schwann cells do. (Slide #83)




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