Normal Brain Histology & Basic Neuropathologic Reactions Flashcards Preview

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Flashcards in Normal Brain Histology & Basic Neuropathologic Reactions Deck (30):
1

What is unique about the CNS? (3)

Selective vulnerability of neuronal systems

Mature neurons are post-mitotic cells

Unique anatomic/physiologic characteristics 

2

What are some unique anatomic/physiolgic characteristics of the CNS? (6)

  • Bony enclosure
  • Metabolic substrate requirements (glucose, O2)
  • No lymphatic system
  • Presence of CSF
  • Limited immune surveillance
    • Physical barrier – BBB
  • Distinctive response to injury & healing (astrocytic reaction) 

3

Normal neurons are integrating & transmitting cells of the CNS, using _______ & _______ means. 

Morphology varies by ______. 

chemical & electrical 

location 

4

What is unique about the nucleus of normal neurons?

  • Most have large nucleus w/ prominent nucleolus
  • Well-defined cytoplasm containing Nissl substance
    • Nissl substance = rER
  • Branching processes (dendrites) & longer cell process (axon)
    • Axons have terminal synapses for chemical transmission to another neuron 

5

Where are these neurons located?

  • Pyramidal & granular neurons
  • Betz cells
  • Granular neurons
  • Purkinje cells
  • Anterior horn cells
  • Globoid shaped cells 
  • Melanin containing cells 

  • Pyramidal & granular neurons
    • Cerebral cortex 
  • Betz cells
    • Primary motor cortex 
  • Granular neurons
    • Hippocampus & cerebellum
  • Purkinje cells
    • Cerebellum
  • Anterior horn cells
    • Spinal cord 
  • Globoid shaped cells 
    • Deep gray nuclei 
    • Basal ganglia, thalamus, brainstem
  • Melanin containing cells 
    • Brainstem
    • Substantia nigra, locus ceruleus 

6

What type of cell is this? 

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Anterior horn cells (motor neuron)

7

What type of cell is this? 

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Cerebral cortex neurons

Pyramidal shape 

8

What type of cell is this?

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Neuromelanin-containing neurons in brainstem

Substantia nigra, locus ceruleus, motor nucleus of vagus 

9

What type of cell is this?

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Granular neurons of the dentate fascia of the hippocampal formation 

10

What type of cell is this? 

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Purkinje cells & granular cells of the cerebellar cortex 

11

_______ accumulates in neuronal cytoplasm w/ age. 

Lipofuscin

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12

Cerebral neocortex (isocortex) contains ____ layers, numbered sequentially from ______ to _______. 

6 layers

superficial to deep 

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13

What is this?

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  • Cerebellum
  • ML = molecular layer
  • PCL = Purkinje cell layer 
  • GCL = granular cell layer
  • WM = white matter 

14

What are the reactions of neurons to injury? (3)

  • Eosinophilic changes (ischemia/hypoxia)
  • Central chromatolysis (axonal damage)
  • Intraneuronal inclusion formation

15

Eosinophilic Degeneration

Definition

Morphologic criteria 

  • Indicated lethal ischemia, hypoxia or hypoglycemia
  • 12-24 hrs to manifest (light microscope level)
  • Morphologic criteria
    • Shrinkage of neuronal cell body
    • Loss of Nissl w/ cytoplasmic eosinophilia
    • Loss of nucleolus w/ nuclear pyknosis 

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16

What is this? 

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Scattered acutely hypoxic/ischemic neurons 

(Eosinophilic Degeneration)

17

Central Chromatolysis

Definition

Reversible or Irreversible? 

Histology 

  • Manifestation of switch from manufacture of synaptic to structural proteins in response to axonal damage
  • Reversible, if axonal repair is successful
  • Cellular swelling w/ margination of Nissl substance & nucleus 
  • Accumulation of filaments & organelles 

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18

What are the 2 types of glial cells of the CNS?

  • “Macroglia”
    • All derived from neuroectoderm
    • 90% of CNS cells
      • Astrocytes
      • Oligodendrocytes
      • Ependymal cells
  • Microglia
    • Derived from bone marrow

19

Astrocytes

Characteristics 

Components

  • Primary replicating cell w/i CNS
  • Round to oval nucleus (10 μm) w/ radiating cytoplasmic processes
  • Star-shaped cytoplasm, normally invisible on H&E staining (unless reacting to injury)
  • Glial fibrillary acidic protein (GFAP) – major cytoplasmic structural protein
  • Ab to GFAP help visualization of astrocytes 

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20

Astrocytes 

Function (4)

  • Contribute to BBB
    • Cytoplasmic processes (end-feet) on blood vessel walls
    • Control flow of macromolecules btwn blood, CSF & brain
  • Responsible for repair & scar formation
  • Maintain extracellular environment
    • Metabolic buffers or detoxifiers & supply nutrients
  • Structural support 

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21

What are reactive astrocytes?

  • Astrocytes activate in response to various pathologic conditions
  • Provides evidence of disease process
  • Astrocytes divide & become larger
    • Increase in GFAP filaments reflected in visible eosinophilic cytoplasm
    • GFAP Ab will help identify the reactive astrocytes
    • Cytoplasm may appear starlike (fibrillary) or large & round (“gemistocytic”) 

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22

Oligodendroglia

Definition

Characteristics 

  • Responsible for myelination in CNS
  • White matter >> gray matter
  • Smaller nucleus & fewer processes than astrocytes
    • Round dense nucleus
    • Peri-nuclear halo (artifact)
  • Do NOT synthesize GFAP
  • Lethal injury --> demyelination

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23

What are 3 important diseases involving oligodendrocytes? 

  • Multiple Sclerosis
  • Progressive Multifocal Leukoencephalopathy
  • Oligodendrogliomas 

24

Ependymal cells (Ependyma)

Characteristics 

  • Cuboidal to columnar glial ciliated cells that line vestibular surfaces
  • Lateral surfaces have cell junctions forming CSF-brain barrier 

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25

Choroid Plexus

Characteristics 

  • Tufts of epithelium projecting into ventricles
  • Secrete CSF
  • Papillary architecture
  • Cell junctions btwn cells ensure CSF-brain barrier 

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26

Microglia 

Definition

Histology 

  • Monocyte/macrophage-derived cells that reside in the CNS
  • Normally inconspicuous, sparse, rod-shaped nuclei w/o visible cytoplasm

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27

What happens to microglia w/ CNS injury?

With CNS injury, may become activated

  • Migrate to site of injury
  • Proliferate
  • May differentiate into tissue MΦ
    • Foamy clear cytoplasm

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28

What happens to microglia w/ viral infections?

HIV?

  • In viral infections, astrocytes & microglia form microglia nodules at sites of neuronal injury
  • HIV infection stimulates cellular fusion resulting in multinucleated giant cells in microglial nodules 

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29

What is the Virchow-Robin space?

What is a Neuropil?

  • Virchow-Robin Space
    • Large arteries w/i the subarachnoid space supply the brain by penetrating into the parenchyma
    • Initially maintain a perivascular space
  • Neuropil
    • Network of dendrites & axons in the gray matter
    • In btwn the cell bodies 

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30

What are Meningothelial Cells?

  • Present throughout the arachnoid membranes covering the brain & spinal cord 

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