Regeneration / Plasticity of CNS Flashcards
What is a critical period an alignment of?
The intrinsic maturation programs and environmental input
What is activity dependent competition?
It is the idea that activity refines the stabilization of synaptic connections
How does maturation affect proneuronal innervation of muscle fibers?
Over time, immature muscle fibers that are innervated by many neurons prunes into a mature muscle fiber innervated by a single neuron
How was neural pruning exemplified with AChR blocking?
AChR blockade was applied to an area of a neuromuscular junction, and the axon branch withdrew from the nonfunctioning receptors which were lost
When does vision segregation begin to occur?
In the womb
What is the reason for vision segregation before the cortex in the LGN?
Spontaneous activity in ganglion cells
What is a Hebbian modification? How does it contribute to the lateralization of the LGN?
It occurs when synapses from two input neurons fire at the same time, and strengthens the synapses with the LGN. Conversely, it weakens crossing over neurons when both neurons form one eye fire and target the correct synapse. This leads to a lack of crossing over.
What happens to the percentage of neurons in layer 3 of the visual cortex after a monocular deprivation?
There is a shift in the ocular dominance group to the open eye, and a blocking of the ocular dominance areas of the closed eye.
The cutting of which axons leads to the inability of the visual cortex to switch ocular dominance groups?
The cutting of the ACh and NE pathways
What happens to monocular deprivation with age?
As aging occurs, the percentage of susceptibility decreases i.e. there is a critical period for monocular deprivation adaptation
What is the remedy for a lazy eye?
Patching
When can we see neural plasticity through environment influences?
Amputation or injury
When are brain wires places/pruned?
Placed before birth, and pruned during infancy
What are the two developmental systems with strong critical periods?
The visual system and the sensorimotor system
When are phantom limb sensations sometimes stimulated? Why?
Phantom limb sensations can be stimulated when a somatotopically bordering area is stimulated, because the remapping/reorganization has not yet fully occurred.
What are the two determinants of neural plasticity?
Genetic connectivity, and experience-dependent reorganization
What are the only two areas of the brain where neurogenesis in adulthood happens?
- The subventricular zone (SVZ) - lateral ventricle
- The sub granular zone (SGZ) - hippocampus
Where in the SVZ is adult neurogenesis observed?
Migration in the rostral migratory system, and genesis in the olfactory bulb
Where in the SGZ is adult neurogenesis observed?
In the granule layer of the dentate gyrus
How does SVZ neurogenesis occur?
New neuroblasts are formed in the stem cells in the lateral ventricle, which migrate down to the olfactory bulb where the neurons are formed.
What is a type 1 cell?
A neural stem cell
What is a type 2 cell?
A proliferating cell
How long does it take for an adult stem cell to differentiate and then survive and fully develop?
Differentiates at 3 days and then reaches final stage at or past 4 weeks
What are the stages of development for a new adult neurogenesis cell? (how long does this take from genesis)
Proliferation(3 days), differentiation(1w), survival (4w+)
What controls the neurogenesis stages?
Neurotransmitters:
Serotonin for proliferation
NE and DA for differentiation
GLU / ACh for survival
GABA inhibitory
What stain is used for stem/progenitor cells? What happens to these stains over time?
BrdU and Thymidine are used, but after 4 weeks the cells divide and dilute the stain
Do progenitors or stem cells proliferate more quickly?
progenitors
What was the result of Carbon 14 dating in the brain?
1.75% of cells were turning over in adult humans
1/3 of hippocampal cells were subject to exchange
How can we identify cell lineages?
With histological antibody markers for different cells that express certain proteins
Why are there differing findings on adult neurogenesis from identification of transcription mRNA involved on neurogenesis?
Humans have a different mRNA marker than other animals
What happens in the hippocampus after a stroke?
There is an increase in the number of newborn cells after a stroke
Where do newborn cells come from after a stroke? Where do they go? What happens to them?
The SVZ cells migrate to the damaged area, but very few of them survive
What are the statistics on cells migrating to stroke areas?
roughly 80% of them die, most of them become astrocytes so there is little actual neurogenesis going on
What are the two regenerative medicinal approaches to brain damage?
- The transplant of induced pluripotent stem cells
- Endogenous neural stem cells (already there)
What is an iPS cell?
An induced pluripotent stem cell (derived from a non-pluripotent cell)
What factors would need to be added to create an iPS from a fibroblast?
4 genes:
Oct 3/4 - differentiation
Sox2 - self renewal
Klf4 - p53, oncogenes (cancer)
c-myc, histone acetylation, oncogene (cancer)
What are the two uses of iPS cells?
- Gene targeting to repair disease-causing mutation
- Screening for therapeutic compounds with testing on real cells
What is an autologous stem cell?
The cells come from the same person who will recieve the transplant
What is the opposite of an autologous stem cell?
An allogenic stem cell is one that comes from a matched or unrelated donor
