Exam 4 - Neural Development Flashcards
Where do neurons come from?
They are produced from the neural tube or neural crest cells
Why are twice as many neurons produced than needed (100,000,000,000)?
Because many will die during development and it is better to have too many neurons than not enough
What regulates the cell migration that needs to occur in order for neurons to get where they need to be?
By hox genes and GABA
Where do synapses form?
Between neurons and target cells
Synapses are maintained/strengthened/lost under what principle?
Use it or lose it
Does synapse regulation only occur during embryonic development?
No, it continues throughout a persons lifetime
Where does axon and dendrite growth occur?
At the tip of a neuron in an area called the growth cone
What are microspikes (filopodia)?
They are extensions of a growth cone which act as “transient” feelers allowing for neurons to find their target cells. By feeling for adhesive molecules (CAM or extracellular molecules)
What happens when a microspike encounters a non-adhesive or even repellent molecule?
The microspike is rapidly withdrawn back into the growth cone
What happens when a microspike encounters an adhesive molecule?
A new growth cone will be set up there and the process will be repeated
In vivo, neurites must break through ECM surrounding the neuron, how do they accomplish this?
By secreting proteases, also axons are packed with microtubules allowing them to punch through the ECM
How do growth cones know what path to follow?
they follow the path of greatest adhesion
What forms the path of greatest adhesion which growth cones will follow?
A continuous pathway of extracellular matrix molecules (these molecules are likely produced by glial cells)
Which neurons can follow a ECM molecule pathway?
Only those containing the right substrate adhesion molecules (SAM)
What does it mean to say that these ECM pathways may be transient?
That it is likely that they only exist for a short period of time.
Why might the same ECM pathway need to be used for multiple neuron to target cells?
Because you don’t have enough genetic power to create a separate pathway for each
What are guidepost cells?
Rather than having a continuous adhesive ECM molecule pathway there are simply spots of adhesive ECM secreted by guidepost cells (glial cells)
How do guidepost cells work in directing a neuron to its target cell?
The growth cone extends microspikes in all directions and once it finds a guidepost a new growth cone is set up here. This process continues until the axon finds its target cell