Neurodevelopment Flashcards
1
Q
Facts about the brain
A
- Brain weight at birth weighs about 350g whereas in adulthood it is about 1300g.
- There are about 85 billion neurons and trillions of synapses in the mature brain.
- At the peak of neurogenesis, 250,000 neurons are born per minute.
2
Q
Germinal stage
A
- The nuclei of the egg and the sperm fuse to form a zygote.
- Zygote starts to divide at 12h, by a process called cleavage, to form a cluster of homogenous cells - morula.
- The morula continues to divide to form a blastocyst (200-300 cells).
- Once implantation in the uterus takes place, the embryonic stage begins.
3
Q
Embryonic stage - gastrulation
A
- Initially - embryonic disc
- Uneven rate of cell development forms three distinct layers:
1. Ectoderm
2. Mesoderm
3. Endoderm - The ectoderm will fold in itself to form the neural tube which will eventually become the nervous system
- Uneven rate of cell development forms three distinct layers:
4
Q
Neural tube defects
A
- Spina bifida - failure of the closure of the neural fold at the level of the spinal cord.
- 1 in 1000 live births
- Small openings can often be surgically corrected
- Larger opening can lead to paralysis and limb deform
- Can be prevented by folic acid supplements
- Anencephaly - brain fails to develop
- Generally results in stillborn
5
Q
Stages of brain development
A
- Cell birth/proliferation (neurogenesis and gliogenesis)
- Cell migration
- Cell differentiation and maturation
- Synaptogenesis and synaptic pruning
- Cell death
- Myelination (myelogenesis)
6
Q
Impact of experience on synapse formation
A
· Experience expectant (Greenough and Black, 1992)
- Development will not happen unless an experience happens during its critical period (the result of evolution and genes) and it is species-specific.
· Experience dependent are not predetermined but are generated in response to the environment
- Vary between individuals i.e., rats in complex environments have more synapses and more new neurons than the ones in standard conditions.
