Week 2 Flashcards
five phases of neurodevelopment
induction of the neural plate neural proliferation aggregation axon growth and synapse formation neuron death and synapse rearrangement
potency after zygote
A fertilised egg is totipotent- develops into any cell After specialisation they become pluripotent- can develop into many but nit all classes Eventually they become multipotent- can develop into different cells of only one class Most developing cells eventually become unipotent- can only develop into one type of cell
induction of the neural plate
3 weeks post conception in all vertebrates
Induced by chemical signals from the organiser (in mesoderm layer)
Tissue taken from the dorsal mesoderm of one embryo (the donor) and implanted beneath the ventral ectoderm of another embryo (the host) induces the development of an extra neural plate on the ventral surface of the host
Neural plate folds to form neural groove, and then lips of the groove fuse to form the neural tube (neural tube defects happen here)
Inside of the neural tube eventually becomes the cerebral ventricles and spinal canal
40 days post conception
3 swellings visible at the anterior end of the human neural tube; develop into fore, mid and hindbrain
stem cells
unlimited capacity for self renewal, can be totipotent, pluripotent or multipoint
Neurons develop from glial cells
When a stem cell divides into two, one becomes a type of body cell and the other is another stem cell which keeps dividing until error happens to stop it
3 layers of embryonic cells
ectoderm, mesoderm, endoderm
neural plate
tissue for NS
a small patch of ectodermal tissue on the dorsal surface of the developing embryo
neural proliferation
After neural tube is formed
Most occurs in ventricular zone, adjacent to ventricle
gives brain its swelling and folding
controlled by chemical signals from two organiser areas in neural tube- floor plate (along midline of the ventral surface of the tube) and roof plate (midline of dorsal surface of tube)
migration
Immature neuron cells (No dendrites or axons) migrate to target location governed by two major factors- specific time and location
cell migration within neural tube
radial and tangential
can use both
radial migration
proceeds from the ventricular zone in a straight line outward toward the outer wall of the tube
tangential migration
at a right angle to radial migration; parallel to the tube’s walls
cell migration out of neural tube
Somal translocation and glia-mediated migration
somal translocation
extension grows from cell in migration direction, explores for attractive and repulsive cues, then cell body moves along extension and removes old ones as it passes
glia mediated migration
radal glia cells appear in neural tube, cells move along this network
Because each wave of cortical cells migrates through the already formed lower layers of cortex before reaching its destination, this radial pattern of cortical development is referred to as an inside-out pattern
neural crest
dorsal to neural tube, formed from cells that break off developing neural tube, develop into neurons and glial cells of PNS
aggregation
mediated by CAMs on the surface of cells
Gap junctions using connexins
Migrated neurons align themselves with others to form structures
axon growth
Axons and dendrites grow
Growth cone at tip of both structures extends and retracts fingerlike cytoplasmic extensions called filopodia, which grow towards target
retinal ganglion cells
compose the optic nerve (Sperry’s experiment on frogs)