copilaria Flashcards
What is plasticity?
The capacity of the nervous system to modify itself, functionally and structurally, in response to experience and injury.
What are the 8 stages of cell development in brain?
- Birth
- Migration
- Differentiation
- Maturation
- Synaptogenesis
- Death
- Rearrangement
- Myelination
What is cell birth?
After 4 weeks of conception, within the neural tube you get neural stem cells.
Every neurone starts as a neural stem cell.
Then they specify later on in their development.
Production of neurones is called neurogenesis.
How does migration happen?
Pioneer axons from the neural tube move out and lay down paths for follower axons to use.
These axons use this path to form multiple connections.
What happens when there is disruption to migration?
If pioneer axons do not migrate to the correct location, this can disrupt brain development.
What is an example of disruption to brain development?
Agenesis.
Agenesis means lack of development.
Agenesis of the corpus collousm is when the corpus develops partly or not at all.
What is differentiation?
The location and the chemical signals in the location where axons migrate to will determine the type of cell they become.
Cells all start as stem cells and then they differ to have specific roles.
What do embryotic stem cells differentiate into?
Embryotic stem cells differentiate into any type of cell in the body
What do neural stem cells differentiate into?
Neural stem cells differentiate into the cell types found in the brain and central nervous system
What is migration?
Brain starts with not that many connections and then neurones start growing and connecting and finding their function within the brain
How many neurones are there in the brain by 7 months of pregnancy?
By 7 months of pregnancy nearly all of the 100 billion adult neurones have been produced.
Yet at birth the brain is a quarter of the weight of the adult brain.
Where does the extra weight of the adult brain come from?
Synaptogenesis (dendrites making connections)
Glial cells
Myelination (axons get fatty layer around to make signals faster and more efficient)
What is synaptogenesis?
Creation of synapses
With age synapses start to decrease due to cell death.
What is cell death?
When neurones that do not make stable connections die.
Those that have made connections stay in place.
Synaptic pruning - number of synapses decrease
What is synaptic rearrangement?
Synapses are not always efficiently connected to the right places so there is a rearrangement to make more efficient and stable connections.
What is myelination?
Starts before birth
Continues up to 30 years of age
Layer around axon to speed up connections
Is plasticity limiteless?
No
Cells are not free to migrate to new areas.
They can make little adjustments in the area they are in .
They do not make large changes in long-distance connectivity.
What are sensitive periods?
There are periods in which certain changes are much more likely to take place.
Sensitive periods generally observed through behaviour are due to neural circuits.
What is axon elaboration?
Axons elaborate during a sensitive period - when you are more likely to learn a certain thing
What is synapse elimination?
After a sensitive period, pruning goes on for those connections that aren’t viable. Then you are left with highly selective connections.
What is synapse consolidation?
Prior to sensitive period, the synaptic connections are vulnerable to death.
After sensitive period, they become more stable and less vulnerable.
What are the limits to sensitive periods?
Not all circuits are shaped by sensitive periods. Some are innate and robust from the start e.g. spinal cord
Some regions demonstrate plasticity throughout life
What happens after sensitive periods?
Circuits become more resistant to change.
Change can still occur but it requires more energy to maintain less stable connections.
Complex behaviours rely on hierarchies of circuits which operate in parallel.
If one goes wrong, complex behaviour will be preserved as other circuits compensate for abnormal processing.
What is an example of sensitive period - visual deprivation?
One of a kitten’s eyes was sewed shut for the first 4-6 weeks of life.
After removing stitches, the visual cells in the deprived eye could no longer process visual stimuli.
Sewing the eye shut after the sensitive period had no effect on vision.
Visual development needs environmental input during sensitive period of neural development.
