Ch. 5: Development of the Nervous System Flashcards
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
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Ectoderm: Neural
- Sensory organs, epidermis, nervous system
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Mesoderm: Bony
- Dermis, muscles, skeleton, excretory system, circulatory system
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Endoderm: Gut
- Gut, liver, pancreas, respiratory system
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Ectoderm: Neural
- 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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