12 week fetus is 90mm
3-week embryo: 3mm
5- week embryo: 10mm
8-week: 22mm
Neural Tube Closure
early neerous develop poses challenges
takes place before women knows she is pregnant
- day 18 and 21
- Ventricular system and spinal cord in adult brain
Differentiation of Neural Tube Week 4-5
Cell division at high rate
- bulges
- Rhombencephalon - Metencephalon and Myelencephalon
- Mesencephalon- no division
- Prosencephalon - Telencephalon and Diencephalon
- Bulk of cerebral hemispheres
- Thalamus, Hypothalamus, and retina (D)
neuruogenesis
brith of new nervous ystem cells
week 8
human looking embryo, diffeentiated spine, fore,mid,hindbrain
developing ventricles
ventricular zone, microglia san cap between and pia mater
between weeks 4-8 clevage lines perpendicular to ventricular zone
7 weeks - parllele ventricular lines
migrates after
migration
11 weeks - fetus for 3
cells migrate away from ventricular xone for cebrebral cortex
- travel in 2 ways
- travel away from ventriuclar zone, releasing glutamate and excitatory, radioglia migration
- tangent to ventricularzone, produce gaba
- some go between both
- Radioglia retract processes, but serve as progneratve sells
Differentiation
- some become more constricted in their paths
- interactions between extracelluar singanlling and genetics
Synaptogenesis: find target
- After differentiation, wiring begins
- intranerous develop neurites tht can sense environment. not official axons yet
- At the end we find a growth cone
- Many factors guide growth cone to cell.
- Pesticulation: adhears to nearby axons going in same direction
- Guidepost cells release chemics that either guide or repel the moving cell.
- Cytoskeleton components develpp stronger structure
Begin a conversation
- Begin communicating chemically, creating a synapse
- first, evenly spaced out, they converge and dip in muscle fiber to form a very strong structure
- kill cells to make sure brai nstays at reasonable size
- prunes chemicals
- Lamellipodia: webbing
- Filapodia: spike
Myelination
Begins prenatally
takes 25 years to complete
makes connections faster and more efficient
forms basis of most motar milestones in childhood
25 y/o+ have better ability to read social environment
frontal lobes myelinated last
Neural Tube Closure: Spina Bifida
Have mobility problems
lump near spine
need folic acid to help prevent
Brain tissue grows outside of skull
Genetic Disorders
Heritable or Parental Age (Mother)
Down Syndrome - related to age of mother
21-29 good age for mother
mid 30s - bad rates for genetic disorder
Toxins
- 0 safe levels of alcohol exposure during pregnancy
- watch out for lead and mercury
- watch out for self introduced toxins