Development of Organisms Flashcards
4 phases of embryo development
proliferation
specialization
interaction
mvt
zygote
divides rapidly into many small cells
these cells depend on the egg yolk for food
inactive genome
blastula
hollow ball of cells
undergoes massive rearrangements to become = gastrula
gastrula
has the 3 embryonic germ layers
germ layers
ectoderm - external
mesoderm
endoderm - internal
fertilization progression of growth
fertilization
zygote
blastula
gastrula
ectoderm
nervous system
epidermis
mesoderm
muscles
CT
endoderm
gut
liver
lung
insides
development decisions are made?
long before the outward appearance begins to change
determined cells
cells that are fated to be one type of cell
despite any environmental changes
completely undetermined cells
cells that change when the environment changes
committed cells
cells that attributes of a cell type but can change if environment changes
positional values
before having their fate determined cells express genetic markers of their location
p value is the position specific character of a cell
instructions for multicellular organisms is contained in ?
non-coding regulatory DNA
____ sequences in DNA are similar in most organisms
coding sequences
it is the non-coding areas that make us unique
asymmetric division
division resulting in 2 unequal daughter cells
such that one could remain a stem cell while other must differentiate
or simply one gets a bunch of nutrients and the other doesn’t
symmetric division
cells are born the exact same but become different due to their specific environmental needs
most important environmental cues
signals from neighbors
these signals could be short or long range
morphogens
long range inductive signals
that can exert gradient effects
morphogens on/off system
require an inhibitor to bind in order to turn off
morphogen gradient formation
localized production of an inducer or inhibitor
morphogen inducer
diffuses away from source exerting an inducing gradient effect
morphogen inhibitor production
an inhibitor signal produced that diffuses away given a gradient effect of inhibiting inducer signals
positive feedback/lateral inhibition
positive feedback amplifies effect of signals
and
is irreversible once started
even if blocking signals are present it is irrelevant
lateral inhibition
delta notch
combinatorial control
response of a cell to signals may differ based on what types of signals are present at that time
combinations create variety
cell memory
effect of a signal depends on previous experiences of the cell
its past may have altered it in some way that now effects how it responds to a signal
sequential induction
different pathways are induced in sequence by formation of different types of signals
ex. a creates b, b creates c, etc.
delta notch signaling
neighbor cell inducing differentiation of its neighbors
delta protein is TM
binds to neighbor receptor ‘notch’
inducing a change in that cell
RTK signaling path
ligand and receptor families
EGF
FGF
Eph
TGFB superfamily signaling pathway
TGFB
BMP
nodal
Wnt signaling path
Wnt
frizzled
hedgehog signaling path
hedgehog
patched, smoothened
Notch signaling path
delta
notch
common signaling pathways summary
pathway names are related to the names of their families
everything else is TGFB
phase 1 - neural development
synthesis of neurons and glial cells
origin of cells = ectoderm
phase 2 - neural development
outgrowth and synapse creation
axons are growing out to make connections
phase 2 - neural development overview
- begin w/ immature neuron
- growth cones move
- growth cones reach target
- target cells release neurotropic factors
immature neuron
cell body w/ indistinguishable dendrites/axons
growth cones
the outward growing of dendrites and axons
each has their own cone
one begins to move faster than the others = axon
axon growth cone
a cone begins to move faster than the others = axon
then develops axon specific proteins
growth cone mvt
via filopodia and lamelopodia
by using actin filament remodeling
control of growth cone mvt
Rho and Rac control the actin remodeling in 2 ways
- extracell matrix
- chemotactic factors
extracellular matrix growth cone control
matrix is sensed by receptors on growth cone
laminin
promotes growth cone mvt
chondroitin sulfate
inhibits growth cone mvt
chemotactic factors - progression
- netrin is secreted
- slit is secreted
- growth cone becomes sensitive to semaphorin
netrin
1st secreted by cells on the floor plate
TRPC receptor on growth cone binds to netrin
netrin binding results
causes Ca channels to open
influx of Ca
causing growth cone to continue to move
slit
2ndly secreted after netrin
by midline cells
‘roundabout’ receptor on growth cone binds slit
slit binding results
slit repels growth cone mvt away from midline
result of secretion of netrin and slit
growth cone is now sensitive to semaphorin
semaphorin
secreted by peripheral body
repels growth cone mvt away from it
resulting in growth cone having narrow path for mvt
results of chemotactic factors
the growth cone now only has a narrow path to move down to reach its target
helps direct the cone in the right direction
once the growth cone reaches its target ?
the target cells must release neurotropic factors
neurotropic factors
required for a neuron to survive once reached its target
~50% of neurons die off due to not getting factors from target
effects of neurotropic factors
short term – help the growth cone
long term – required for survival of neuron
NGF
nerve growth factors
bind to TrkA receptors on growth cones
to promote survival of specific neurons
phase 3 - neural development
remodeling thru life
continues thru adult life
creating new synapses from learning
phase 3 depends on
electrical acitivity and synaptic signaling
synaptic signaling
an external event that causes at least 2 neurons to be activated at the same time
synaptic remodeling
response to activation of 2 or more neurons
Ca influx thru NMDA receptors
dendrite spines are remodeled
NMDA receptor
glutamate receptors on dendrites
allowing influx of Ca
which causes transcriptional factors to be turned on to result in physical changes of synapse
neurons that fire together
wire together
