Brain Development Flashcards
Germinal Stage
first 2 weeks
- repeated cell division
- attaches to mother’s uterus about 10-14 days after conception
Prenatal Stage: Germinal period
- zygote divides forming a blastocyst, a hollow ball of 150 cells
- week 2, fully embedded in uterine wall and 250 cells
Embryonic Stage
2-8 weeks
- organogenesis from differentiated layers of blastocyst
- amnion and chorion form from outer layer of blastocyst
- cells from interior of blastocyst: ectoderm, mesoderm, endoderm
ectoderm
brain and spinal cord
mesoderm
muscles, bone, cartilage
endoderm
gastrointestinal tract
placenta
contains membranes that allow nutrients to pass from the mother to the umbilical cord
umbilical cord
contains blood vessels that carry nutrients and oxygen to the embryo, carries waste from embryo back to mother
28 day embryo
- recognisable head
- first formulation of a spinal cord (neural tube)
32 day embryo
brain is developing fast
44 day embryo
started to sprout arms and legs
Fetal stage
- 9 weeks to birth
- from parts of first trimester to last trimester
- muscles strengthen, bodily systems develop
age of viability
23 weeks
When survival outside the uterus is possible if the brain and respiratory system are sufficiently developed
cell body
the cell’s life centre
dendrites
receive messages from other cells
axon
passes messages away from the cell body to other neurons, muscles or glands
myelin sheath
covers the axon of some neurons and helps speed neural impulses
when do sulci and gyri develop
7 months
prenatal development and CNS
structural formation of CNS
-Interruptions, via genetic mechanisms or interuterine trauma or infections, likely to have significant impact on cerebral structure, so that brain’s morphology appears abnormal even at a macroscopic level
Postnatal development of the CNS
with elaboration of the CNS, in particular, dendritic arborisation, myelination, and synaptogenesis. Although still largely genetically regulated, these processes are thought to be more susceptible to the impact of neuronal activity and thus to environmental and experiential influences
sequence of brain development
- Hierarchical progression
- Cerebellar / brain stem areas mature first
- Posterior —> anterior
stages of brain development
- Formation of the neural tube (neurulation)
- Cell birth (neurogenesis; gliogenesis)
- Cell migration
- Cell differentiation
- Cell maturation (dendrite & axon growth)
- Synaptogenesis (formation of synapses)
- Cell death & synaptic pruning
- Myelogenesis
Formation of the neural tube
- The neural tube forms soon after conception: during the third week of gestation (embryonic period)
- Formation of a hollow tube that develops into CNS (i.e. spine and brain)
- Tube slowly closes over
- Inside tube neurons and glia develop and migrate