Neurodevelopment Flashcards
what are the 5 events of neurodevelopment
neuralation, vesiculation, migration, cytodifferentiation, synaptic connections
how many days after conception does the pre-embyronic stage begin/last
1-14
what is the main purpose of the pre-embryonic stage
cell division
is the highway that cells migrate along in the neural tube
radial glial cells
what is the timeline for the embryonic stage
day 15 - 8th week
formation of 3 primary germinal layers
gastrulation
what are the 3 germinal layers that are formed during embryonic stage
ectoderm (outer), mesoderm (middle), endoderm (inner)
what structures does ectoderm form
epidermis, nervous system, pharyngeal arches, muscles of mastication and swallowing, structures of inner ear
what structures does mesoderm form
dermis, connective tissue, vascular structures, bone marrow, internal organs (heart and kidneys), myotomes, dermatomes, sclerotomes, urogenital system
what structures does endoderm form
respiratory, gut, liver, pancreas
formation of neural tube
neuralation
what days does neuralation occur
18-26
what starts the process of neulation
notocord
the notocord comes from which layer
mesoderm
development in which the neural tube forms after notocord has signaled for the start of this process, what is the order of formation of the structures
neural plate plate, neural grove, neural tube, neuropores
development in which the neural tube forms after notocord has signaled for the start of this process, what is the order of formation of the structures
neural plate plate, neural grove, neural tube, neuropores
neural crest forms CNS or PNS
PNS
neural tube forms CNS or PNS
CNS
which neuropore begins brain formation/precursor brain
superior
formation of the brain
vesciluation
around what day does vesiculation occur
28
what are the 3 enlargements called during vesiculation
vesciles
what are each of the 3 ventricles called during vesiculation
hindbrain, midbrain, forebrain
what structures will form from the hindbrain
medulla, pons, cerebellum
what structures will form from the forebrain
cerebral hemispheres, thalamus
openings at either end of the neural tube
neuropores
what day does the superior neuropore typically close at
25
what day does the inferior neuropore typically close at
27
failure of neuropores to close at all or at the appropriate time can lead to
neural deficits (hydrocephalus, anencephaly, myelomenigocele)
what layer do neural crest cells arise from
ectoderm (neuroectoderm)
segmentation of body regions
somites
what layer do somites come from
mesoderm
are somites related to CNS or PNS structures
PNS
precursor brain forms from which end of neuropore
superior neuropore
spinal cord develops from which end of neural tube
inferior neuropore
vesiculation of the neural tube results in the development of CNS structures (brain and spinal cord) during which weeks
3-5
why do the names of the brain change during vesiculation week 3-5
changes in structure and function
telencephalon and diencephalon
forebrain
olfactory (smell), hippocampus (memory storage), cerebrum (association/intelligence0)
forebrain (Telencephalon)
optic vessel (vision/retina), epithalmus (pineal gland), thalamus (relay center for optin and auditory neurons), hypothalamus (temp, breathing regluation, sleep)
forebrain (diencephalon)
fiber tracts between anterior and posterior brain, optic lobes, and tectum
midbrain
metencephalon and myelencephalon
hind brain
cerebellum (coordination of complex muscular movements), pons (fiber tracts between cerebrum and cerebellum)
Hindbrain (metencephalon)
medulla (reflex center of involuntary activities
hindbrain (myelencephelon)
what weeks does the fetal stage occur
8-40
Supporting cells of the peripheral nervous system responsible for the formation of myelin
schwann cells
Type of glial cell in the CNS that wrap axons in a myelin sheath
oligodendrocytes
what are the 5 things that occur during fetal stage
cell proliferation, migration, cell aggregation, cell differentiation, synaptic connections
dependent on DNA coding, growth factors, hormones, cell-to-cell interactions
cell proliferation
cells develop further into their function; neurons and glial cells develop from neuroblasts inside the neural tube
cell proliferation
what drives cell proliferation to form neurons and glial cells
DNA
when do most neurons develop (85-100 billion)
5th week and 5th month
support cells
glial cells
differentiated functions of various CNS structures is dependent of proper acquisition of the right position for each neuron
cell migration
help neurons migrate from germinal layer of neuroepithelium to their target locations
radial glial cells
what do radial glial cells degenerate/transform into after migration is complete
astrocytes
what is the speed of cell migration
tens of micrometers per hour
somites differentiate into these three layers
sclerotome, myotome, dermatome
vertebrae and skull
sclerotome
skeletal muscle
myotome
dermis
dermatome
what cells migrate via cell adhesion molecules in extracellular matrix/”piggy back” on cell walls of other migrating cells
neural crest
the predetermined blueprint that guides neurodevelopment
DNA encoding
where does DNA encoding occur in each cell
nucleus
what two intra and extracellular factors cause activation/suppresion of genes that guide DNA encoding
homeobax genes (HOX genes) and growth factors
control time sequence of development events by switching other genes on/off; “windows of opportunity” that allow development to proceed normally at specific time period, signaling cells release signaling molecules that tell other cells how to proceed; target cells receive these enzymes and encoded message
homeobox genes
signaling molecules
growth factors
proteins and enzymes that bind with specific receptor molecules on designated target cells
growth factors
growth factors direct what two processes
induction and apoptosis
target cell differentiation into different types of cells
induction
programmed cell death
apoptosis
during what processes does the brain make more synaptic connections than needed
cell migration and synaptogenesis
once cells have migrated to their proper DNA encoded position they form nuclear or laminar arrangements called
functional aggregates
in the spinal cord and brainstem cells aggregate into vertical columns known as _____ in a somatotopical organization
fiber tracts
cortical structures also aggregate into somatotopical arrangements (2 names)
motor and sensory homunculus
formation of synapses
Synaptogenesis
insures the main function of the nervous system can occur which is communication
Synaptogenesis
what things drive synaptogenesis (path finding)
DNA, mechanical routing, protein, chemicals, electrical
mechanical routing (ex: radial glial cells)
sterotropism
via protein mediators on axonal membranes (ex: piggy backing)
contact guidance
chemical attraction between axon and target membranes
chemotropism
electrical activity along axonal and target membranes steer axons in desired directions
galvanotropism
selective apoptosis weeds out weaker synapses in order to make room for more complex ones to develop
synaptic pruning
during what time period does myelination occur
fetal 4th month until 2 y/o (and beyond)
axons will not be fully functions until they are fully _____
myelinated
times in development when axons are competing for synaptic sites
critical periods
example of critical period
language
nervous system damage that occurred perinatally may not be evident until the damaged system would have been normally become functionally
growing in deficit
during what period is the CNS most susceptible to major malformations/developmental disorders
day 14 - week 20
what are the 5 classifications of CP classified by motor dysfunction
spastic, dyskinetic, ataxic, hypotonic, mixed
permanent non-progressive damage to developing brain
cerebral palsy
no vertebral formation to protect spinal cord
Myelomeningocele (spina bifida)
myelomeningocele occurs when the _____ neuropore fails to close
inferior
myelomeningocele occurs when there is a materal deficit of
folic acid
no brain, no protection form skull or meninges
anencephaly
anencephaly occurs due to failure of ____ neuropore to close
superior
anencephaly usually occurs due to
chromosomal abnormalities