Brain development Flashcards
What are guidance signals interpreted by?
Growth cone
act via concentration gradients of morphogens
What are non-diffusible guidance signals ?
short range
sub derived
ECM or on target cells (cadherins and ephrins)
What are diffusible guidance signals ?
Long range
act as gradients
Netrins, semaphorins
What are growth cones ?
hand like structures
at the tip of growing axons and dendrites
receptor on surface
senses guidance cues
What is the role of the cytoskeleton in responding to guidance cues ?
Microtubules reinforce the structure, pilloponea project out
Actin filaments for movement
polymerisation = direction o growth cone
How do we know about guidance signals ?
Cell culture experiments
How do repulsion and attraction work together?
Long attraction interplay of attraction and repulsion to drive growth to midline
Switch to repulsion at midline to be pushed forward
How are synapses formed ?
Adhesion mols stabilise formed connections
Presynaptic neurexins: org SV docking zone
Post neuroligins: recruit PSD
What determines the synapses worth keeping?
Neurotrophins + electrical activity
How do axons navigate ?
Via intermediate targets
Axons grow along another as guides
What are the transient structures of brain development ?
Notochord, floor plate and roof plate
What does the anterior end turn into after neurogenesis ?
The brain
What does the neural tube near somites turn into after neurogenesis ?
Spinal cord
What structure is a major part of the PNS ?
Neural crest
How do neurones become different ?
High degree of patterning in neural tube
Patterning along the anterior (rostal) and posterior (caudal) length of tube
What are morphogens ?
Activate/ repress transcription factors
Are secreted molecules (extracellular)
Work via gradients
What part of the brain distinguishes humans from other animals ?
The size of the cortex, especially frontal lobe.
Distinguishes personality and decision making
What causes differentiation ?
Morphogen gradients
Distance from secreting cells (gradients) / availability of ligand and presence of receptors determines the response of the cell
What are the 5 steps of neurogenesis ?
Neural plate develops from overlying ectoderm
Plate folds inward and closes neural tube
Floorplate about notochord
Where tube closes = roof plate
Neural crest plate on top
What are hox genes ?
Family of transcription factors
Establishes segmentation along anterior-posterior axis
How is the cortex built ?
Migration
Neuroepithelium progenitor cells in neural tubes (neural precursor cells) form the ventricular zone
What do radical glia do?
Connect ventricular and pial surface
What are neuroblasts ?
precursors of a nerve cell, undifferentiated
which migrate to pial surface to make the marginal zone
Why is the cortex described to be built inside out ?
Newer neuroblasts migrate past the older ones
What are the two places the glia remain?
- Remain attached to lumen + become ependymal cells (product of spinal fluid)
- Move to marginal layer + form astrocytes or oligodendrites
What do astrocytes do?
Repair and maintenance
