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What is the time frame for neurodevelopment?
After conception until 10 years of age
Name the 6 progressive events in neurodevelopment:
- cell proliferation
Name the regressive events in neurodevelopment:
In the stages of development archicerebellum -> paleocerebellum -> neocerebellum; what are each parts referring to?
- archicerebellum= floulonobular lobe
- paleocerebellum= vermal region
- neocerebellum= cerebellar region
What regions develop first?
caudal vs. rostral
primitive vs. higher regions
peripheral vs. midline
- primitive regions
True or False:
Time of neurogenesis predicts time of functional maturity.
FALSE- it does NOT predict the time of functional maturity
What are the 4 developmental stages that come before birth?
What are the 5 developmental stages after birth?
- old age
When does the preembryonic stage occur?
conception to two weeks
What is the solid sphere called that forms a cavity in the middle, during the preembryonic stage?
Where does fertilization occur during the preembryonic stage?
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.
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.
When does the embryonic stage of development occur?
during the 3rd-8th week
What does the ectoderm form?
- sensory organs
- nervous system
What does the mesoderm form?
- circulatory systems
What forms the liver, gut, pancreas, and respiratory system?
During the embryonic stage, what is the emphasis on?
When is the fetal stage?
8th week until birth
During what stage of development is the emphasis on growth of existing systems?
When does myelination begin and what is it?
- Begins in fetal stage through 1st-2nd decade of life
- insulation of axons by fatty tissue
About what day does the notochord develop and what are the reminants of it today?
- Day 16
- reminants are nucleus pulposus of intervertebral disc
Follow the development of the nervous system
notochord --> neural plate --> neural groove --> neural tube --> neural crest (lies dorsal/lateral to tube)
How does the neural plate form?
It forms by epidermal cells dividing like crazy
How does the neural groove form?
cells drop down and form it, the edges of the plate fold
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
Where do the cells of the neural crest lie?
dorsal/lateral to the tube
By what day has the nervous system formed?
What are the motor and sensory portions of the neural tube?
- Basal plate: ventral region- motor
- Alar plate: dorsal region- sensory
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
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
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)
- Pancreatic islet cells
- Craniofacial muscles, bone and connective tissuee
What does the hindbrain form?
What does the mylencephalon form?
- Lower medulla
- 4th ventricle
- central canal
What does the metencephalon form?
- Upper medulla
- 4th ventricle
What does the midbrain form?
What does the mesencephalon form?
- cerebral aquaduct
What does the forebrain form?
What does the diencephalon form?
- thalamus region (thalamus and hypothalamus)
- 3rd ventricle
What does the telencephalon form?
- cerebral hemispheres
- lateral ventricles
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
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
What can Arnold Chiari Malformation Type 2 cause?
- death from anacephaly- the cranial end doesn't close
- malformation of brainstem and cerebellum
What is the main problem in spina bifida?
there is a neural tube defect
Describe Spina Bifida Occulata:
- Least dangerous
- protrude through the bony defect, but the spinal cord is still completely functional
Describe Spina Bifida (Cystica) Meningocele:
- meninges protrude through
- may or may not have symptoms
Describe Spina Bifida (Cystica) Meningomylocele:
- neural tissue with meninges protrudes through
- causes abnormal growth and degree of lower extremity dysfunction
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
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