L7:brain development Flashcards
What must be in place to produce neurons?
A precursor structure must be in place
The neural tube will develop into the CNS.
What do the main divisions of the CNS develop into?
The ventricles
Early in development, these divisions appear as distinct sections.
From where do neurons and glia originate during development?
Neural stem cells at the ventricular surface
This occurs from 5 weeks to the 5th month after gestation.
What is the first step in the development of neurons?
Cell proliferation
This involves division of undifferentiated stem cells.
What happens during a vertical split of a stem cell?
Both daughter cells repeat the process
This allows for further proliferation of stem cells.
What occurs during a horizontal split of a stem cell?
One daughter cell repeats the process while the other moves away and will not divide again
This leads to differentiation of one of the cells.
When do the processes of cell proliferation stop?
Almost completely weeks before birth.
What is the second step in the development of neurons?
Cell migration
Different cells have different places of origin.
From where do pyramidal cells and astrocytes originate?
More ventral areas
These cells migrate laterally.
How is the cortex structured?
Organised in structured layers
The cortex is not a single, homogenous sheet.
What do radial glia cells do during cell migration?
Extend thin processes towards the surface
They create an ordered pattern that maps the cortex.
In what order do developing neurons migrate to the cortical plate?
First to layer VI, then V, then IV, etc.
Interneurons move in sideways.
What is the first problem that growing axons face?
Finding the right direction.
How do growing axons find their direction?
Guided by chemical signals in the environment.
What is the second problem that axons encounter?
Finding the right target structure.
What guides axon development towards target structures?
Chemical signals.
What is the third problem for axons?
Finding the right target cell.
What do sensory and motor cortices form?
Maps
Important for action control.
What is the general strategy for synapse development?
Overabundance and pruning
Initially, far too many synapses develop.
What happens to unsupported synapses during pruning?
They disappear.
What strengthens supported synapses?
Correlated activity
When both the presynaptic and the postsynaptic neuron are active at the same time.
What happens to connections when pre and post synaptic neurons are active at independent times?
Connections weaken
This is referred to as uncorrelated activity.
How is prenatal correlated activity established?
Through spontaneous waves or retinal activity.
What is necessary for both eyes to coordinate visual input?
Actual visual input is needed.
What must newborn babies do to learn to see?
They must learn to see.
