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What is the time frame for neurodevelopment?
After conception until 10 years of age
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Name the 6 progressive events in neurodevelopment:
- cell proliferation
- growth
- migration
- extension
- connection
- myelination
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Name the regressive events in neurodevelopment:
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In the stages of development archicerebellum -> paleocerebellum -> neocerebellum; what are each parts referring to?
- archicerebellum= floulonobular lobe
- paleocerebellum= vermal region
- neocerebellum= cerebellar region
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What regions develop first?
caudal vs. rostral
primitive vs. higher regions
peripheral vs. midline
- rostral
- primitive regions
- midline
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True or False:
Time of neurogenesis predicts time of functional maturity.
FALSE- it does NOT predict the time of functional maturity
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What are the 4 developmental stages that come before birth?
- preembryonic
- embryonic
- fetal
- perinatal
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What are the 5 developmental stages after birth?
- infancy
- childhood
- adolescence
- adulthood
- old age
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When does the preembryonic stage occur?
conception to two weeks
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What is the solid sphere called that forms a cavity in the middle, during the preembryonic stage?
blastocyte
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Where does fertilization occur during the preembryonic stage?
uterine tube
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When does the embryonic disk form in preembryonic development?
The blastocyte implants in the endometrium, and the inner cells of that become the embryonic disk.
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What are the bilaminar and trilaminar disc?
- The bilaminar disc forms from the embryonic disc. It is 2 layers, the ectoderm and endoderm.
- The trilaminar disc forms from the bilaminar disc, it adds another layer the mesoderm.
- From the mesoderm the notochord forms, and then the ectoderm proliferates to form the neural plate.
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When does the embryonic stage of development occur?
during the 3rd-8th week
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What does the ectoderm form?
- sensory organs
- epidermis
- nervous system
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What does the mesoderm form?
- dermis
- muscles
- skeleton
- excretory
- circulatory systems
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What forms the liver, gut, pancreas, and respiratory system?
endoderm
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During the embryonic stage, what is the emphasis on?
development
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When is the fetal stage?
8th week until birth
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During what stage of development is the emphasis on growth of existing systems?
fetal stage
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When does myelination begin and what is it?
- Begins in fetal stage through 1st-2nd decade of life
- insulation of axons by fatty tissue
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About what day does the notochord develop and what are the reminants of it today?
- Day 16
- reminants are nucleus pulposus of intervertebral disc
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Follow the development of the nervous system
notochord --> neural plate --> neural groove --> neural tube --> neural crest (lies dorsal/lateral to tube)
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How does the neural plate form?
It forms by epidermal cells dividing like crazy
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How does the neural groove form?
cells drop down and form it, the edges of the plate fold
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When and how does the neural tube form?
- 18-24 days
- It forms when the neural groove detaches and the sides of the groove come together
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Where do the cells of the neural crest lie?
dorsal/lateral to the tube
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By what day has the nervous system formed?
Day 30
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What are the motor and sensory portions of the neural tube?
- Basal plate: ventral region- motor
- Alar plate: dorsal region- sensory
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What are the three layers of the neural tube and their significance?
- Ependymal layer: inner layer, line the ventricle
- Mantle layer: become gray matter, make up basal and alar plate
- Marginal layer: outer wall, develops into white matter, consist of axon and glial cells
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What do the three different aspects of the somite form?
- anteromedial part: sclerotome- becomes skull and vertebrae
- posteromedial part: myotome- becomes skeletal muscle
- lateral part: dermatome- becomes dermis
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What are the 8 things the neural crest forms?
- dorsal root ganglion
- post-ganglionic cells of ANS
- Schwann cells (myelinated cells of nervous system)
- Chromaffin cells of adrenal medulla
- Meninges (pia and arachnoid)
- Melanocytes
- Pancreatic islet cells
- Craniofacial muscles, bone and connective tissuee
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What does the hindbrain form?
- mylencephalon
- metencephalon
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What does the mylencephalon form?
- Lower medulla
- 4th ventricle
- central canal
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What does the metencephalon form?
- Upper medulla
- pons
- cerebellum
- 4th ventricle
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What does the midbrain form?
mesencephalon
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What does the mesencephalon form?
- midbrain
- cerebral aquaduct
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What does the forebrain form?
- diencephalon
- telencephalon
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What does the diencephalon form?
- thalamus region (thalamus and hypothalamus)
- 3rd ventricle
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What does the telencephalon form?
- cerebral hemispheres
- lateral ventricles
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What do trophic factors do? (basic)
- Find the right chemical attractions between pre and post synaptic cells. If any part because damaged, connections won't be able to be made
- function of the neurons not determined until connections are made
- myelination must occur for neurons with long axons to be functional- myelination occurs in 4th fetal month till age 10ish
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What is the main problem in Arnold Chiari Malformation Type 1?
- herniation of the cerebellar tonsils through the foramen magnum into the vertebral canal
- symptoms often: headache, nausea, the 4D's
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What can Arnold Chiari Malformation Type 2 cause?
- death from anacephaly- the cranial end doesn't close
- malformation of brainstem and cerebellum
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What is the main problem in spina bifida?
there is a neural tube defect
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Describe Spina Bifida Occulata:
- Least dangerous
- protrude through the bony defect, but the spinal cord is still completely functional
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Describe Spina Bifida (Cystica) Meningocele:
- meninges protrude through
- may or may not have symptoms
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Describe Spina Bifida (Cystica) Meningomylocele:
- neural tissue with meninges protrudes through
- causes abnormal growth and degree of lower extremity dysfunction
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Describe Spina Bifida (Cystica) Myeloschis:
- Malformed spinal cord is open to surface of the body
- neural tube fails to close
- no motor function below level of damage
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What are 5 of the critical periods
- Neural tube formation (3-4 wk utero): anacephaly, Arnold, Spina
- Brain Enlargments (2-3 mth utero): holoprosencephaly
- Cellular Proliferation (3-4 mth utero): FAS
- Neural Migration (3-5 mth utero): heterotopia, seizure
- Organization (5 mth utero-childhood): mental retardation, trisomy 21, cerebral palsy
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