At what time after conception does neurodevelopment begin?
Begins AT conception (zygote)
List the 4 dev. processes
In what order do they occur?
Proliferation
Differentiation
Migration
Organization
Not sequential: they happen more or less simultaneously, as in proliferation still happening as the other three occur
What is proliferation as dev. process?
Cells divide
Differentiation?
Cells become specific cell types (neurons, glia, muscle cells, skin cells, blood cells, …)
Migration as a dev. process
Cells migrate/ move to the correct location, eg. skin cells move to the outside
Organization as dev. process
Cells organize into functional units, eg. Motor unit, cardiac system, brain circuit
When does induction begin?
After 2 weeks (organism bow called embryo)
What is induction? Name 2 processes and say which layer of cells in embryo is most important
Primary and secondary neurulation
Ectoderm
Describe primary neurulation
- in mesoderm, notochord forms
- part of ectoderm is induced by notochord to become the neural plate; neural fold forms
-> ectoderm defaults to neural cells; chem. signals from notochord inhibit: BMPs (bone morphogenic proteins)
Chem signals (eg. proteins noggin or chordin) inhibit BMPs in sone places -> neural plate
Describe secondary neurulation
Neural plate grows, forms neural groove; neural fold closes, forming neural tube (future CNS) and around/ on top of it neural crest (future PNS, eg neurons with mechanoreceptors)
Outer layer ectoderm becomes skin
How common are neural tube defects? When do they usually occur (temporally)?
2 per 1000 births globally
During 2nd neurulation
What factors into etiology of spina bifida?
Genetics (10% of cases, eg Trisomy 13)
Other risk factors:
deficit in folic acid/ Vit. B9 (high deficit almost guaranteed NTD)
Maternal diabetes, obesity, hyperthermia, drugs (eg. A Med for epilepsy), nutritional deficiencies
What happens in spina bifida?
Neural tissue protrudes more or less severely into skin tissue
List the 5 phases of neurodevelopment in order
-Induction
-Proliferation
-Migration and Aggregation
-Axonal Growth and Synapse Formation
-Maturation
What is occulta spina bifida?
Neural tissue protrudes into skin but is still covered by skin
Usually asymptomatic or very mild symptoms,
Hardly noticeable, often patch of hair on the back
Meningiocele?
Form of spina bifida, closed defect
Neural tissue protrudes into skin and forms a bulge on back where meninges push out into skin; bulge usually just fluid filled
Symptoms can be pain, sensitivity, sensory and motor symptoms
Myelomeningiocele?
Spina bifida open defect
Bulge on skin and neural tissue protrudes into bulge
Symptoms can include paralysis/ paresis, chiari malformations (cerebellum protrudes into/ towards spinal cord outside skull); 80% have hydrocephalus (enlarged head);
Impacts the development of the brain stem (functions: arousal, critical functions) -> can be fatal
