Embryology II Flashcards
How many neurons and glial cells are there in the brain?
10^12
How many cells are in the neurectoderm?
10^5
How many synapses are in the brain?
10^15
How many miles of axons are in the brain?
10^6
Neural cells are generated in ______________.
ventricular zones (areas of the developing brain that are immediately adjacent to a ventricle)
Where are the secondary zones of neurogenesis?
- Subventricular zone: gives rise to cells in the olfactory bulb
- External granule layer: gives rise to the granule neurons in the cerebellum (primarily postnatal)
- Dentate gyrus: part of the hippocampus that gives rise to cells involved in learning and memory
Describe the differences in migration of ventricular and subventricular cells.
Ventricular: migrates directly to the nearest layer
Subventricular: migrates to the furthest layer
Track the movement of the nucleus in a cell dividing in the ventricular zone.
G1: remains halfway between pia and ventricular layer
S: moves up toward the pia
G2: moves back to the halfway point
M: detaches from the pia and shrinks down toward the ventricular layer
During mitosis on the ventricular zone, how does division differ between cells that leave the cell cycle and cells that remain in the cell cycle?
Those that exit the cycle will have a horizontal division (in which one cell is closer to the pia) – producing an asymmetric division – and those that remain in the cycle will have a vertical division – resulting in a symmetric division.
The __________ gives rise to all the cells of the peripheral nervous system.
neural crest
Most of the neural crest cells that migrate through the dorsal pathway become __________.
pigment cells – not neurons
The neural crest cells that become PNS neurons migrate __________.
ventrally (that is, ventral to the dermatomes)
What receptors on neural crest cells guide migration?
Integrins
Which ligands bind to integrins on neural crest cells?
Laminin and fibronectin
Olfactory cells arise from the subventricular zone in a feature called the ____________, a type of chain migration.
rostral migratory stream
GABA-ergic interneurons arise from __________ migration, from ganglionic eminences.
tangential
Neurogenesis begins after what embryonic process finishes?
After the neural tube folds
Why do dividing neural cells move during the phases of the cell cycle?
The reason is not known.
Most of neurogenesis occurs prenatally, but there are three exceptions. What are they?
1) Cerebellar granule cells
2) Olfactory cells
3) Hippocampus cells
The secondary-zone neurogenesis cells also arise from ______________.
ventricular zones; however, they migrate without exiting the cell cycle
Division of ventricular cells in a plane parallel to the ventricle surface can lead to unequal protein allocation. This process is thought to play a role in cell differentiation. Which three proteins have demonstrated this effect?
Prospero
Numb
Miranda
The first layer of ventricular cells to become postmitotic is the _________ layer (around week 8-9).
preplate
The preplate then divides into what four layers (from outermost to innermost)?
Marginal zone, cortical plate, subplate, and intermediate zone
Mutations in the filamin A protein can lead to a condition called ___________.
periventricular heterotopia
