Development of neurons Flashcards
What stages do neurons have to go through?
Cellular determination, proliferation, migration to their correct locations, axonal project (axon sent out to make way through various tissues to connect to target), establishment of connection to target, pruning unnecessary connections, death of excess neurons that are generated during development.
What must be studied in order to understand development of the nervous system?
Development in general - look at fertilisation etc.
What are the layers of the gastrula?
Outer layer (ectoderm), inner layer (mesoderm), and further inner layer (endoderm).
What are the most important layers in development of the nervous system?
The ectoderm and the mesoderm.
How are cell of the ectoderm determined to become neurons?
Neural induction - these induction signals come from the mesoderm.
What happens when determination of neurons has occurred?
Cells of the ectoderm will differentiate to become neurons or remain as precursor cells.
When does migration of neuronal precursor cells occur?
Before differentiation to a neuron is complete.
What induction signals are present in the etoderm?
Signals that prevent formation of neurons - there are inhibiting signals. Neural induction is the inhibition of inhibition signals from the ectoderm in order to form neurons.
What is organogenesis?
The process in which different layers become rudimentary organs.
What does organogenesis involve?
Folding, splitting and dense clustering of embryonic cells.
What are the first rudimentary organs formed from organogenesis?
The neural tube and the neural crest.
What cell layer gives rise to the neural plate?
The ectoderm.
What do the neural tube and neural crest give rise to?
Most of the cells of the nervous system.
What is the neural tube formed from?
The folding inwards of the neural plate which is an area of the embryo that is determined in development.
What is the xenopus laevis?
The clawed frog.
What does it mean that the frog embryo is polar?
There is a ventral and dorsal surface.
What is the Spemann organiser?
A region of the mesoderm that contains cells that release neural inducers such as Noggin, Chordin, Follistatin and Cerebrus.
What happens if a region of the ectoderm (animal cap) is transplanted onto a second embryo?
The frog would grow a second nervous system.
What does fertilisation trigger intracellularly?
An influx of calcium that sweeps across the egg and causes a rapid release of cortical granules to form the fertilisation envelope to block polyspermy.
When are the vegetal and animal regions determined?
When the egg is fertilised - this is determined by the point of entry of sperm into the cell.
What does the vegetal pole allow, compared to the animal pole?
The vegetal pole allows the entry of calcium which plays a role in signalling inside the egg to change where molecules are distributed.
What does the point of entry of sperm also determine?
A second positional axis - ventral (where the sperm entered), and dorsal (opposite to the entry point).
What does cortical rotation do?
It mixes cytoplasmic determinants and creates the dorsal-ventral axis. It redistributes maternal cytosolic determinants that are partitioned in different dividing embryonic cells.
What is the grey crescent?
The future blastopore.