Ch. 5: Development of the Nervous System Flashcards Preview

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Flashcards in Ch. 5: Development of the Nervous System Deck (21):

When does the Preembryonic stage take place?

What do you look like during this time?

  • Conception to 2nd week of gestation
  • A disk that will become you

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When does the Embryonic stage take place?

2nd to 8th week of gestation


What transformations happen in the Embryonic Phase?

  • Organs begin to form from embryonic disk
    • Ectoderm: Neural
      • Sensory organs, epidermis, nervous system
    • Mesoderm: Bony
      • Dermis, muscles, skeleton, excretory system, circulatory system
    • Endoderm: Gut
      • Gut, liver, pancreas, respiratory system
  • Neural tube forms and closes
  • Brain begins to form


When is the Fetal Phase?

8th week gestation until birth


What happens in the Fetal Phase?

  • Brain formation continues
  • Myelination begins

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What are the phases of Nervous System Formation?

  • Phase 1: Neural Tube Formation
  • Phase 2: Initial Brain Formation


What is the Neural Plate?

Neural cells, flat - needs to round out to form

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What is the Neural Groove?

Forms as outside of disk begins to mound up

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What is the Neural Tube?

What was flat has now rounded up to form a circle

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What are Neuropores?

  • Rostral and Caudal openings of neural tube (not yet closed)
  • Failure to close: can cause Spinabifida or Anencephaly

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What is the Neural Crest?

  • Pockets of cells at edgs where disk mounds up
  • Form outside of closed tube & dorsal root ganglion
  • Morphology: pseudo-unipolar

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What is the Mantle Layer?

  • Inner Ring
  • Nervous System cell bodies

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What is the Marginal Layer?

  • Outer ring
  • Axons and glia


  • Non-neural support cells when tube closes
  • Protective ring around neurons

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What is a Somite?

What develops from it?

  • Somite (mesoderm): small balls, 31 on each side, becomes:
    • Sclerotome: vertebrae & skull
    • Myotome: skeletal muscle
    • Dermatome: skin

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What 2 plates form from the Mantle Layer Divisions?

What do these plates control?

  • Motor Plate → motor neurons → ventral horn → becomes Myotome (innervated by 1 segmental spinal nerve)


  • Association Plate → interneurons and sensory neurons → dorsal horn → Dermatome

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What 4 things does the neural crest diversify into?

  1. Peripheral sensory neurons
  2. Myelin cells (Shwann cells)
  3. Autonomic neurons
  4. Endocrine organs


In initial brain formation, what are the 3 part of the brain?

What do those 3 part develop into?

  1. Hindbrain - medulla, pons, cerebellum
  2. Midbrain - stays midbrain
  3. Forebrain - forms everything else (cerebral cortex, cerebellum, basil ganglia, etc)


As the brain develops, where does the mantle layer (or cell bodies) migrate to?


  • Migrate to outside of brain
    • more surface area from folding


What is differentiation?

When do neurons differentiate in the brain?

  • Specialization
    • once they arrive at their final location


How long does it take Myelination to develop in the brain?

What is the result of undeveloped Myelination?

  • Up to 3 years!!
    • Result: born uncoordinated 


Why do some neural deficits take years to develop?

  • Will not notice symptoms until use of that part of the brain is needed.
  • "Grow into defecits"