Ch.4/Development Stuff Flashcards
What does the Nervous System form from?
Ectoderm - outermost cell layer
Stage 1 of development in the NS
Neurogenesis - division of nonneuronal cells to produce neurons
Stage 2 of development in the NS
Cell migration - movements of nerve cells to establish distinct populations
Stage 3 of development in the NS
Cell differentiation - refining of cells into types of neurons/glial cells through gene expression
Stage 4 of development in the NS
Synaptogenesis - establishment of synaptic connections as axons grow
Stage 5 of development in the NS
Neuronal cell death - selective death of many nerve cells
Stage 6 of development in the NS
Synapse rearrangement - loss of some synapses & development of others, thru lifespan
Forming of the NS
Thickening of ectoderm > neural plate
Neural plate forms Neural groove (dip)
Groove closes & forms neural tube
Tube forms spinal cord & brain
Neural tube defects
Spina Bifida doesn’t close properly, so spinal cord & fluid bud out of body
-Causes: lack of folic acid; alcohol, nicotine
Teratogen
Things that lead to birth defects
When do major divisions of CNS develop
18 days - three layers of cells: endoderm, mesoderm, ectoderm
20 days - neural groove begin - closed @ 22
25 days - 3 major brain divisions, fore, mid, hindbrain
Where does mitosis occur
Ventricular zone
How does environment determine cell type?
o Encountering high Shh – becomes glia
o Encountering med Shh – motor neuron
o Encountering low Shh - interneurons
Synaptogenesis - how influenced by chemicals
Formation of synapses
Cells attracted via chemicals & forms synapse
NGF - promotes axon survival
Neurotrophins
Family of proteins essential for development of vertebrate NS
Apoptosis
Neurons die by failure to compete for chemicals
How do synapses change over lifespan
Weak contacts eliminated, stronger kept/stren
Affected by experience
Common effects of teratogens
Congenital heart defect, neural tube defects, polydactyl
Types of teratogens
Chemicals, infection, external/internal environment
Adult neurogenesis
Generation of new neurons in adulthood
~700 daily
Alzheimer’s effect on brain
-Shrinking in frontal, temporal, aprietal
-Amyloid plaques
-Neurofibrillary tangles
-Loss of many neurons in basal forebrain - makes Ach
Organization of cerebral cortex
-Formatted in layers because neurons migrate on radial glia, final position correlated to Bday
