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


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


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


What is the Neural Groove?

Forms as outside of disk begins to mound up


What is the Neural Tube?

What was flat has now rounded up to form a circle


What are Neuropores?

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


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


What is the Mantle Layer?

  • Inner Ring
  • Nervous System cell bodies


What is the Marginal Layer?

  • Outer ring
  • Axons and glia


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


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


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


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"