Chapter 9: Neural Development Flashcards
zygote stage
after conception, cells of the fertilized egg start to multiply. lasts for two weeks
neural plate
primitive neural tissue
formation induced by the underlying organizer tissue
what are the organizer tissues of the neural plate?
ectoderm layer (develops into skin), mesoderm layer (develops into muscle), endoderm layer (develops into internal organs)
neural tube
formed by the neural plate folding over
what does the neural tube become?
central nervous system
what does the neural crest become?
peripheral nervous system
spina bifida
failure of the neural tube to close completely, resulting in a portion of the spinal cord remaining uncovered.
can usually be corrected at birth, in severe cases baby will not walk
anencephaly
front end of the neural tube does not close leading to failure of the forebrain to develop.
baby usually only lives for a few days
when does the embryo stage occur
onward from 14 days until the fetal stage
what can stem cells do?
replicate themselves and differentiate into any one of many types of cells
what is found in the subventricular zone?
lining of neural stem cells surrounding the ventricles
what are progenitor cells?
multi-potent cells
what can a progenitor cell become?
a neuroblast or a glioblast
what are the two types of cell migration out of the subventricular zone?
radial migration (straight outward)
tangential migration (side to side; less defined)
how many layers are there in the neocortex?
6, with the 6th layer being populated first
what do radial glial cells do?
lay a path outward to other parts of the brain, allowing cells to migrate along them
what is the purpose of reelin?
a signalling protein that signals cells to aggregate exactly where they need to be
what are the steps of cell aggregation?
- cells reach where they’re supposed to be and start to tangentially migrate to fit into their exact spot
- differentiate into different cells when they are in their proper spot
what do neuoblasts turn into?
interneurons or pyramidal neurons
what do glialblasts turn into?
oligodendroglia or astrocytes
how do young neurons start to mature?
- axonal growth: extend their axons to nearby targets to initiate synapse formation (develops quickly)
- dendritic growth: sprouts dendrites to provide surface area for synapses with other cells (develops slowly)
what does chemical signalling allow for?
allows growth to occur precisely
synaptogenesis
the genesis of new synapses
growth cones
develop the early pathways (such as the visual pathway)
fasciculation
lay down a signaling pathway for the growth cones to follow and re-enforce
filopodia
extend outward to detect chemical signals
when does the fetal stage occur?
onward from 9 weeks until birth
what occurs during the fetal stage?
new neurons and glia continue to be born, migrate, differentiate, and mature
when does the human brain begin to develop gyri and sulci?
8 months into development
postnatal development
the brain continues to develop after birth in response to environmental stimuli, neurons continue to mature, and myelination is taking place
synaptic pruning
occurs throughout childhood to create stronger pathways and better connections by reducing unnecessary connections
