Nervous system development 1-4 Flashcards
non-bilaterian nervous systems
placozoa and porifera have no nervous systems (though porifera have some vaguely neural cell types), ‘neural net’ structures emerge in cnidaria/ctenophora
example of a less centralised bilaterian nervous system
nerve chord organisation- hemichordates, platyhelminthes, nematodes etc
example of centralised nervous systems
protostomes, e.g. annelids, molluscs
chordates, e.g. vertebrates
potential importance of gastrulation in bilaterians
site of gastrulation/Wnt gradient ‘flipping’- from animal to vegetal side
example of paterning similarities between arthropod and vertebrate
drosophila and mouse brain patterning by the same stuff- Otx for forebrain/equivalent, Hox along spinal cord, Pax genes in middle etc
example of cell polarity being important
Neiukoop centres- difference in TF expression opposite the sperm entry point- Dischevelled/betacatenin are expressed, helps support Wnt signalling and to establish an early patterning gradient
example of cross-repression
FGF/RA along the hindbrain to form rhombomeres
vertebrate innovations
DV progenitor zones, multiple cell layers, neural crest
what contributes to differentiation of cells into brain parts
graded Wnt activity, inducing fore, mid, and hindbrain activity
protein involved with Shh in neural tube patterning
Shh and Gli work in a feedback loop to pattern sections along the neural crest (* needs work)
examples of gene expression in specific regions helping to establish boundaries
Otx- brain in vertebrates
Hox- spinal cord
Pax- brain in verts/inverts
neural crest boundary is formed by
Otx2 (no NC) and Gbx2 (NC) along a Wnt gradient
hysteresis
idea that signals which have already been recieved are included in determining cell fate
key ideas in pattern formation
tipping points
scalability
hysteresis
integrating information both spatially and temporally
