Plasticity & regeneration COPY Flashcards
GENE EXPRESSION
i) what are inducing factors? name the two ways they can act
ii) name three things inducing factors modify? why is cell position in development critical?
iii) what is competence?
iv) name three things that competence depends on
i) inducing factors are signalling molecules provided by other cells
- can be freely diffusible > act over long range
- can be tethered to cell surface and act locally
ii) inducing factors modify gene expression, cell shape and motility
- position of cell determines which inducing factors its exposed to > dictates cell fate
iii) competence is the ability of a cell to respond to inducing factors
iv) competence depends on exact set of surface receptors
- transduction molecules
- transcription factors expressed by the cell
NEUROGENESIS
i) what is it?
ii) what time period does it occur in? what week does the neural tube form?
iii) which germ layer does the nervous system arise from?
i) process by which neurons are generated
ii) occurs in 5th week-5th month of gestation
- NT forms at week 3
iii) ectoderm
NEURAL STEM AND PROGENITOR CELLS
i) which area are neural stem cells found in?
ii) give two properties of these cells (what is their renewing capacity and what can they give rise to?
iii) can neural progenitor cells self renew continuously?
iv) what cells can neural progenitors give rise to? give an eg
i) neural SCs found in the ventricular zone (lines ventric sys)
ii) infinitely self renewing
- after terminal division and differentiation they can give rise to full range of cell classes in the nervous system (multipotent)
iii) incapable of continuing self renewl
iv) neural progenitors can only give rise to one specific cell type until its mitotic capacity is exhausted
- oligodendroglial progenitor can only give rise to oligodendrocyte
DIVIDING PRECURSOR CELLS
i) which two areas do precusors move between before they give rise to neuroblasts and progenitor cells?
ii) at the start of division - which surface to cells in the ventricular zone reach up and migrate to?
iii) how many copies of DNA does the cell contain before it moves back down to the VZ?
iv) once the cell is back in the VZ - what happens to its projections? what process does the cell then go through?
v) what does the fate of the daughter cell depend on?
i) between the ventricular and marginal zone
ii) cells in the VZ reach up and migrate to the pial surface
iii) cell grows and nuclei contains 2 copies of DNA before it moves back down to the VZ
iv) once back in the VZ it retracts its arms from the pial surface and undergoes division
v) whether the cleavage is symmetrical or asymmetrical
FATES OF CELL DIVISIONS
i) what two daughter cells result from an symmetrical division? which result from an assymertical division?
ii) which signalling molecule is located at the superior pole of the precursor cell? what role does this molecule play? which is located at the inferior pole?
iii) which signalling molecules are therefore present in the daughter cells of symmetrical division?
iv) which signalling molecules are present in daughter of asymmetrical division? which one will migrate away? why?
v) which type of cleavage occurs early in development? which occurs later in development?
i) symmetrical division > two neural stem cells
assymetrical divison > a neuroblast + progenitor cell
ii) sup pole = notch (activates gene expression that inhibits division and migration fron the VZ)
inf pole = numb
iii) symmetrical div = 2x neural SC = both numb and notch
iv) assym = neuroblast (notch) and progenitor cell (numb)
- neuroblast will migrate away as it contains Notch
v) early dev = symmetrical > neural SCs as lots of cells still need to be produced
later dev > assym = NB and progenitor
PRECURSOR CELL DIVISION
i) label signalling molecules A and B
ii) label cell types C,D,E
iii) which of these cell types will migrate away? which one has limited mitotic potential
i) A = notch 1 B = numb
ii) C = neural stem cells, D = neuroblast, E = progenitor cell
iii) neuroblast will migrate away and progenitor has limited mitotic potential
NEUROBLASTS
i) what are they? what will they differentiate into?
ii) what is the fate of the migrating neuron determined by? (3)
iii) which signalling molecule does it contain which instructs it migrate away?
i) postmitotic, immature nerve cells that will differentiate into a neuron
ii) fate determined by - age of precursor cell
- position in the ventricular zone
- environment at time of division (which signals are present)
iii) notch causes it to migrate away
DEVELOPMENT OF THE CORTEX
i) where do cells begin? what is the first later to be generated? what is the last layer to be generated?
ii) what do the first cells to migrate become? what does this form for the rest of the cells?
iii) where do the second cells to migrate move past? what do they then become?
iv) what plate is the boundary before the marginal zone?
v) which two plates dissappear after all layers are formed?
i) cells begin in the ventricular zone
- first layer to be generated is layer 6 and the last is layer 1
ii) first cells to migrate become the subplate which forms a scaffold for the rest of the cells
iii) second cells migrate and move past the subplate and become the cortical plate
iv) the cortical plate is the boundary before the marginal zone
v) after all laters have formed the subplate and cortical plate dissappear
DEVELOPMENT OF THE CORTEX
i) label A-D
ii) what happens to the neuroblasts once all layers are developed? how do they do this?
i) A = ventricular zone, B = subplate, C = cortical plate,
D = white matter
ii) once all layers have developed the neuroblasts will differentiate by sprouting neurites (axons/dendrites)
NEUROBLAST DIFFERENTIATION
i) name two structures that allow the neuroblast to grow and move
ii) where does a retinal ganglion cell need to migrate to? name the three steps in which it does this
iii) give an example of a chemoattractant? what do they do?
iv) give an example of a chemorepellant? what do they do?
v) what will happen to cells moving along a surface lined with chemoattractants or repellents?
i) growth cone and filopodia
ii) retinal gang cell needs to migrate to the thalamus then the LGN
- pathway selection (thalamus), target selection (LGN), address selection (correct layer in LGN)
iii) chemoattractants = netrin
- promote growth to a specific chemical source over distance
iv) chemorepellant = slit
- turns growth the opposite way to the source
v) cells moving along a surface lined with attractants = growth cone will extend along it
- lined with repellents - makes the growth cone retract
CHEMOATTRACTION AND CHEMOREPULSION
i) where are netrins released from in the spinal cord? what effect do they have on spinal thalamic axons?
ii) where is slit released from? what is its associated receptor?
iii) what effect does slit have on sensitivity of the growth cone to netrin? what does this allow?
iv) what information do spinal thalamic axons relay?
i) from the ventral surface in the midline of the spinal cord
- influence the growth of spinal thalamic axons from dorsal horn to the ventral midline
ii) slit is released just adjacent to the midline
- assoc receptor is robo
iii) slit stops the growth cone responding to netrin once its crossed the midline
- this means that once the GC has crossed the midline is does not cross back
v) spinal thalamic axons relay pain and temperature information
TROPHIC INTERACTIONS
i) give an example of a neurotrophic factor?
ii) how to inputs get to a target neuron? what is required to happen when they arrive?
iii) how is competition for trophic factors reflected? why is this necessary?
iv) by which mechanism allows refinement of connections made by neurons and target cells?
i) NGF
ii) neurons follow a chemoattractant to the target cell
- need to refine the amount of connections made
iii) competition for trophic factors is reflected in selective apoptosis - produces proper match in number of pre and post syn neurons
iv) selective apoptosis
SYNAPSE ELIMINATION
i) what does synaptic capacity lead to? when does it peak and when does it decline?
ii) in what time period are most synapses lost?
iii) which receptors are selectively lost pre synaptically? which two steps does this involve?
iv) which step happens before the axon branch is withdrawn?
v) name another way that a synapse can be eliminated
i) synaptic capacity leads to each neuron receiving a finite number of synapses
- peaks in early development and decreases during maturation
ii) most are lost during adolescence
iii) selective loss of pre synaptic Ach receptors
- involves dissembly of the receptor then retraction of the axon branch
iv) Ach R loss post synaptically
v) can also eliminate synapses by blocking the receptor with a toxin (loss of AchRs then withdrawal of axon branch)
CRITICAL PERIODS AND MODIFICATION OF BRAIN CIRCUITS
i) do the first steps in constructing brain circuitry rely on electrical activity?
ii) once electrical activity is established what is important in temporal windows called critical periods?
iii) what concept underlies critical periods? give an example
iv) what are the two important factors for success completion of the critical period?
i) no - they rely on intrinsic and cellular mechanisms
ii) activity mediated influences on the developing brain are most consequential in critical periods
iii) critical periods = variable time window for different skills and behaviours to be developed eg sensorimotor skills
iv) two important factors for completion = availability of appropriate influences eg exposure to language
- neural capacity to be able to respond to the influences
OCULAR DOMINANCE COLUMNS/VISUAL DEPRIVATION
i) what layer of the primary visual cortex are these found?
ii) what do they indicate about thalamic input? how can they be visualised?
iii) what does the visual deprivation task show?
iv) what happens when a cat is given three days of visual deprivation during a critical periods? which eye is activation shifted to?
v) what effect does visual deprivation have on the adult?
vi) which other animals has this also been seen in?
i) layer 4
ii) indicate seperate thalamic input for each eye
- vis by injecting a RA tracer > transported along the visual pway > LGN > visual cortex > corresponds to that eye
iii) vis dep task shows that development of visual perception requires sensory experience within the critical period
iv) visual deprivation during a critical period causes a significant shift in cortical activation to the non deprived eye
v) visual deprivation has no effect on an adult
vi) macaque monkeys
