development Flashcards
how does the neural cord form?
groove in the neural plate forms
this deepens and the edges come together to form the neural cord underlying the ectoderm (breaks free of overlying ectoderm)
which part of the laminar disc becomes the nervous system
part of the ectoderm
what is the order of the closing neural tube down the embryo?
- first = exactly the middle - then zips upwards and downwards
- second = top of the head - zips backwards and forwards
- third = forehead from bottom to top
- fourth = nape of the neck
- fifth = bottom of the spine
what are the two major congenital defects that are caused by an error in the fusion of the neural tube
ancephalopathy
spina bifida
which end of the neural tube swells? and what are the 3 vesicles called
the rostral end
- prosencephalon
- mesencephalon
- rhombencephalon
explain the further segmentation of the 3 vesicles of the neural tube?
prosencephalon - splits into telencephalon and diencephalon
rombencephalon splits into metencephalon and myeloencephalon –> 7 segments
how are the retina formed
as optic vesicles from the diencephalon
what does the diencephalon form in the adult human brain
thalamus and hypothalamus
what does the telencephalon form in the adult human brain
cortex, basal ganglia and hippocampus
what does the metencephalon form in the adult human brain
pons and cerebellum
what does the myelencephalon form in the adult human brain
medulla
what are the derivatives of the neural crest cells
- peripheral nervous system (DRG, sympathetic and parasympathetic ganglia, enteric ganglia and Schwann cells)
- melanocytes
- muscle, cartilage and bone of skull, jaws, face and pharynx
- dentine
what is the direction of migration of neural crest cells
rostral to caudal - following specific paths
where are the stem cells of the embryo brain
at the ventricular surface
how does the cortex get its layers?
stem cells at the ventricular surface of the neural tube proliferate and are placed on the outside
further proliferation –> placed on the outside
(inside–> out building of the layers)
what directs the proliferation of neural cells from the stem cells of the ventricular surface of the neural tube to its destination on the outside of the layers?
the radial glia
act as scaffolding to direct cells to the outer part of the cortex
what are two major genes that influence migration of neural cells during the proliferation of the cortex? What do their deficiences cause?
Reelin - hardly any cells in the cortex (less white matter)
DCX - smooth surface (not convuluted)
how does fragile X syndrome cause male autism
mutation of fragile X mental retardation gene –> affects synaptic and dendritic development
what is the prime organiser of the spinal cord and how does it do this?
the notochord - it releases signals (eg sonic hedgehog) that affects the cells of the neural tube closest to it –> makes them become the floorplate
what is the role of the floorplate in the induction of the spinal cord
it releases sonic hedgehog to induce the formation of the ventral horn motor neurons
what do ventral motor neurons do in regards to development of the spinal cord
release motor neuron factor to induce interneurons just dorsal to the motor neurons
how do axons grow?
the axons is towed into position by a growth cone which follows a gradient of diffusible and membrane bound signals
what is the growth cone of axons made up of
actin and microtubules
what does the refinement of the nervous system lead to
permanent changes that establish mature functional nervous system.
Refinements based on the early experiences of the nervous system - making and breaking connections
what is the critical period for neural cortex plasticity
the amount of time you have for a certain refinement of a particular part of the cortex
why dont you become blind in both eyes if you cover them both at birth?
because the plasticity of the neural cortex depends on the relative neural activity of both of the eyes (not absolute)
