development part 1 Flashcards
Development
the complex process of turning a single fertilized egg into a fully-‐formed animal
initially, what are embryos?
undifferentiated sheets of cells.. (organisms have polarity, where does this come from?)
‘primitive streak’
establishes the axes of the developing embryo: divides left from right and anterior from posterior
The neural folds fuse to create the ______
Neural tube
How do the neural folds fuse?
from the middle outwards
Problems with neural tube development: Anencephaly & spine bifida.
At the rostral end problems with the process cause anencephaly at the caudal end, closure defects cause spine bifida.
differentiation
the process where a less specialized cell becomes a more specialized type of cell. Largely a process of customizing transcription, tuning gene expression to create different cell types.
the closed neural tube expands into ______
3 bulges or “three primary brain vesicles”
What is neural development all about?
elaboration of the three primary brain vesicles into more complex structures.
three primary brain vesicles
secondary vesicles of the forebrain
As the telencephalon (‘cerebrum’) develops it expands ______ and ______ to sit to the developing mid- and hind‐brain.
laterally and caudally.
dorsal.
Differentiation of the telencephalon
Differentiation of the telencephalon
Differentiation of the telencephalon
Differentiation of the telencephalon
A mouse with a spontaneous genetic mutation in the ‘reeler’ gene has _______. Specifically, _______
disorganized brain structure.
lamination is altered.
for circuts to form correctly several things must happen…
- ) Neurons must be born in the right place and time (neurogenesis)
- ) Axonal projections must grow enabling them to target the appropriate cells
- Specific synaptic connections must form
Transcription
factors
proteins that rgulate the expression of genes.
They can positivly and negitivly regulate target gene expression, ot work in concert with a widerange of co-regulators to finely tune gene expression.
Radial glial cells
project from the ventricular to pial surface.
Neuroblasts, born via horizontal cleavage at the ventricular zone, migrate up the radial glia, forming the layers of the cortex: subplate, cortical plate, layer VI, V, IV, III, II, I.
Note: deeper layers first!
Unlike most projection neurons, interneurons and oligodendrocytes
migrate _______ into the cortex
Laterally
Areas of cortex are distinguishable by ______ features
cytoarchitectural
Transplantation experiments demonstrate that one type of cortex (visual) can be differentiated into another (somatosensory).
This suggests that the ______ helps define specific cytoarchitecture in the developing cortex
input recieved.
Growing retinal axons must choose three things correctly
- Pathway: Which way to turn at
the optic chiasm? - Target: When you get to the
correct structure (here the
thalamus), which nucleus do
innervate? - Address: Of all the neurons
within the target nucleus, which
one(s) do you synapse with?
Lamellipodia
sample the environment, driven forward by dynamic
growth of filopodia.
Filopodia
grasp the substrate at appropriately
coated areas to pull the growth cone forward.
fasciculation
Axons can grow towards common targets together, thanks to
fasciculation, or the tendency to stick together. Axons are bound
together via cell adhesion molecules (CAMs).
growing axons are steered by _____________
external guidance cues
what are axon external guidence cues
Substrates that can be either attractive or repulsive to axons, directing their growth. The environment can also contain diffusible chemoattractant and chemo-repellent signals.
what must happen for a chemoattractant or repellant to work?
cells must express its receptor.
can receptor expression be changed?
receptor expression can change in response to the
environment. This lets axons can be attracted and repelled by the same structure.
The chemoaffinity hypothesis and axon
patterning
Retinal axons project to the tectum in the frog in a “retinotopic” manner.
This means retinal axons preserve spatial information by innervating specific parts of the tectum.
They do this by differentially responding to
chemo-repellents.
How do Antagonistic gradients refine targeting?
Often, axons are targeted with antagonistic gradients of chemoattractants and chemo-repellants. By varying the amount of receptors for each of these, final destinations can be precisely encoded.
The growth cone of a motor neuron secretes _______
agrin
Agrin interaction with MuSK on the muscle cell membrane causes _______
acetylcholine receptor clustering.
interactions between the basal lamina and the
motor neuron lead to _____ and ______.
calcium entry.
neurotransmitter release.
Neurulation creates a _______.
‘neural groove’
optic cup anatomy
The ‘optic cup’, which becomes _____,
grows from the diencephalon which becomes ____
the retina (in the back of the eye).
the optic nerve.
development of mid-brain (pic)
Rostral Development of the hindbrain
caudal development of the hindbrain (pic)
blastula
The fertilized egg divides, forming a multi-‐cellular blastula.
a hollow sphere of cells, referred to as blastomeres, surrounding an inner fluid-filled cavity.
gastrulation
cells of the blastula fold inward and enlarge to form the gastrula.
3 distinct layers of tissue in the gastrula
ectoderm, mesoderm, endoderm
the central nervous system develops from the _____
ectoderm.
where is there a cross over in the central nervous system?
Pyramidal decussation in the medulla
Axon guidance is ____ between intermediate targets
dynamic
Neuroblasts differentiate into _______
mature brain cells
In response to diverse chemical inputs, neuroblasts differentiate into __________
neurons (early), astrocytes (later) or oligodendrocytes (last)
what is associated with Maturation?
major transcriptional changes that precede morphological changes.
Regions of the human brain
have stereotyped _____.
connectivity.
How do Neural precursors divide?
stereotypiclly
what happens if a precursor cell is cut horazontially?
bottom stays as precursor.
the top goes to become a neuron or glia
what happens if precursor cell is cut vertically?
both halfs stay as precursor cells.
