Nervous System Flashcards
Major Developmental Processes
- induction
- proliferation
- pattern formation
- determination
- intercellular communication
- cell migration
- cellular differentiation
- synapses
- stabilization or elimination
- progressive development of integrated patterns
neural plate
thickened ectodermal structure overlying the notochord ; formed by blocking BMP4 by noggin and chordin
brain boundary determining signals
Otx-2 expressed at forebrain-midbrain region; Gbx-2 expressed in the hindbrain region
boundary is called the isthmic organizer; releases FGF-8 and Wnt-1 from this border region affects Hox gene expression
cranial and caudal neuropores
unfused regions of the neural tube; closure spreads cranially and caudally; closure occurs in region where earliest somites appear
earliest divisions of brain
prosencephalon, mesencephalon and rhombencephalon
cephalic flexure
appears at the end of third week at the level of mesencephalon; cephalic end of embryo is bent into a C shape
cervical flexure
brain doubles back on itself at the cephalic flexure; cervical flexure appears at the beginning of the fifth week at the boundary between the hindbrain and the spinal cord
external limiting membrane
basal lamina surrounding the neural tube; where DNA synthesis takes place
postmitotic neuroblast
will eventually become neurons and begin to produce cell processes that ultimately become axons and dendrites
bipotential progenitor cell
gives rise to either neuronal lineage progenitor cell or glial lineage progenitor cell
nestin
expressed by multipotential stem cells; downregulated as descendants of bipolar progenitor cells separate into neuronal progenitor cells (express neurofilament protein) and glial cells (express glial fibrillary acidic protein)
neuronal progenitor cells and lineage
give rise to earliest bipolar neuroblasts, which have two slender cytoplasmic processes that contact the external limiting membrane and the central luminal border of the neural tube
unipolar neuroblasts accumulate large masses of RER in their cytoplasm and begin to send out several cytoplasmic processes, becoming multipolar neuroblast (send out axons and dendrites until they reach their target areas and become mature neuron)
glial progenitor cells and lineage
==> O-2A progenitor cell (will give rise to oligodendrocytes and type 2 astrocytes)
==>progenitor that will give rise to type 1 astrocytes
==> radial glial cells (guidewires in the brain for migration of young neurons)
radial glial cells
while neurons move along them, they are inhibited from proliferating; after the neurons are done, radial glial cells reenter mitosis
==>type 1 astrocytes
==>various specialized glial cell types
==>ependymal cells
microglial cells
serve phagocytic function after damage to brain; immigrant cells derived from primitive myeloid precursors
not found in developing brain until it is penetrated by blood vessels
