Neural development and plasticity Flashcards
During development what are the 5 stages of nervous system maturity?
Neurogenesis migration and differentiation axon guidance synaptogenesis activity dependant refinement
Outline neurogenesis
Occurs between day 2-20 of development, the neural plate is invaginated, and pinched off - forming the neural tube.
The outside of this tube is the pal surface and Pia cells grow from here to the luminal surface - develop into neuroepithelial cells. through symmetric division.
asymmetric division causes neuroblast cells to be produced.
Outline migration and differentiation.
Morphogens control what cell types are produced. Chemical guidance signals signal the neuroblast cells where to migrate to. Morphogens then switch on the genes.
As the neuroblasts migrate towards the Pia - they locate themselves in waves, with earliest migrants further from the outside with each successive wave.
What are the three zones of neuroblasts? And what cortical structures arise from each zone.
Marginal - most superficial (other cortical areas)
Cortical - middle (structures that receive subcortical and cortical inputs.)
Subplate- most deep (subcortical matter)
How does axon guidance work?
filopodia extend from the axon tip and grow towards chemical guidance signals, the growth cone at the tip of the axon have receptors for the guidance signals.
These guidance signals arise from the floor plate . At contact with the floor plate a change in gene expression within the axon occurs. - less attractive receptors, more repulsive. this causes growth to stop
Why do growth cones only grow towards tissues they can stick too?
The filopodia (composed of actin) need to bind to the extracellular matrix in order to move. Therefore cytoskeleton mutations disrupt cortical development.
What is synaptogenesis?
This is where axons make contacts with other axons within close proximity, if complementary surface proteins link up they stabilise the connections and synapses form.
if the surface don’t link then the filopodia retract and synapses don’t form.
What is activity dependant refinement? Outline how it works.
Where axons are strengthened or weakened according to their use.
IN the synapse there is both AMPA- fast ligand gated gluR and NMDA - ligand gated gluR blocked by Mg++.
If a new synapse is not in much use there will be little activation of gluR and NMDA will remain blocked.
In an active circuit then many synapses will activate causing postsynaptic depolarisation. NMDA receptors unblock causing Ca++ influx.
This Ca++ influencex increases number and effectiveness of AMPA receptors - strengthening the axon.
What is synaptic plasticity?
The ability of a synapse to strengthen or weaken according to use.
How does plasticity change during maturity?
Exceptionally high in babies, remains high during childhood and is low in adults.
Therefore children adapt to changes in body functions affecting one side of the body (e.g. eye compromised) better than adults
Why is maladaptive plasticity thought to be a cause of pathological pain?
Where during cortical remapping, post trauma the maladaptive reorganisation of the brain causes responses to stimuli that aren’t there
