T1 L20 Plasticity & regeneration

Question 1

What are inducing factors?

Answer 1

Signalling molecule provided by other cells
Freely diffusible, exert action over a long range
Tethered to cell surface acting locally
Modify gene expression, cell shape & motility

Question 2

What is competence?

Answer 2

Ability of a cell to respond to inducing factors

Question 3

What does competence depend on?

Answer 3

Exact set of surface receptors
Transduction molecules
Transcription factors expressed by the cell

Question 4

What is neurogenesis?

Answer 4

Process by which neurons are generated

Question 5

What are neural stem cells?

Answer 5

(Neural precursor cells)
Infinitely self renewing
After terminal division & differentiation they can give rise to full range of cell cases within relevant tissues

Question 6

What is a neural progenitor cell?

Answer 6

Unable to continually self-renew
Capable to give rise to only one class of differentiated progeny

Question 7

Give an example of a neural progenitor cell

Answer 7

Oligodendroglial progenitor cell gives rise to oligodendrocytes

Question 8

Where is the nucleus in G1?

Answer 8

Near the ventricular surface

Question 9

Where is the nucleus in S?

Answer 9

Migrate toward pial surface & DNA replicates

Question 10

What happens in G2?

Answer 10

Cell grows & nucleus migrates towards lumen

Question 11

What happens if there is a symmetrical division in mitosis?

Answer 11

Generates 2 neural stem cells by dividing vertically

Question 12

What happens if there is an asymmetrical division in mitosis?

Answer 12

Generate a neuroblast & progenitor cell by dividing horizontally

Question 13

What is a neuroblast?

Answer 13

Postmiotic, immature nerve cell that will differentiate into a neuron

Question 14

What factors determine fate of migrating neuron?

Answer 14

Age of precursor cell
Position in ventricular zone
Environment at time of division

Question 15

What are the 3 stages to the growth cone?

Answer 15

Pathway selection
Target selection
Address selection

Question 16

Give an example of a pathway selection

Answer 16

Retinal ganglion cell reaching correct thalamic location

Question 17

Give an example of a target selection

Answer 17

Selective the appropriate thalamic nucleus

Question 18

Give an example of a chemoattractant

Answer 18

Netrin

Question 19

Give an example of a chemorepellent

Answer 19

Slit

Question 20

Where is netrin secreted from and what happens after it is secreted?

Answer 20

By cells in ventral midline of spinal cord

Axons with appropriate netrin receptors are attracted to region of highest netrin concentration

Question 21

Where is slit secreted from and what happens after it is secreted?

Answer 21

By midline cells.

Axons expressing the protein robs grow away from the region of highest slit concentration

Question 22

Give an example of a neurotrophic factor

Answer 22

Nerve growth factor

Question 23

What is synapse elimination?

Answer 23

Synaptic capacity
Selective loss of acetylcholine receptors
Muscle fibre initially receives input from several alpha motor neurons but during development all but one input are lost.
Postsynaptic acetylcholine loss precede withdrawal of the axon branch

Question 24

What are the intrinsic cellular & molecular mechanisms involved in the first steps of conducting brain circuitry?

Answer 24

Establishment of distinct brain regions
Neurogenesis
Major axon tracts
Guidance of growing axons to appropriate targets
Initiation of synaptogenesis

Question 25

When is the activity mediated influence most consequential on the developing brain?

Answer 25

During temporal windows (critical periods)

Question 26

What are the critical periods?

Answer 26

Variable time windows for different skills / behaviours

Question 27

What are the requirements for successful completion of the critical period?

Answer 27

Availability of appropriate influences

Neural capacity to respond to them

Question 28

What are some hypotheses for why critical periods end?

Answer 28

Less potential axon growth
Synaptic transmission matures, less potential changes here
Constraint cortical activation

Question 29

How does the visual cortex adapt in the blind?

Answer 29

Starts responding to somatosensory signal

Question 30

Describe peripheral nerve regeneration

Answer 30

Macrophages clear debris from degenerating peripheral stump
Schwann cells proliferate
Express adhesion molecules on their surface & secrete neurotrophins & other growth-promoting signalling molecules
Parent neuron of regenerating axon expresses gene that restores it to a growth state

Question 31

Describe central nerve regeneration

Answer 31

Local cellular changes at or near injured sites including degeneration of myelin & other cellular elements
Clearing of debris by microglia
Local production of inhibitory factors by astrocytes, oligodendroglia & microglia
Glial scar formation

Question 32

What are the barriers to regulation after cortical development?

Answer 32

Less neurogenesis
No migration
No radial glial cells
Neuronal plasticity is restricted
Parenchymal glia don’t generate neurons & become reactive after neurodegeneration
Axon pathfinding molecules may be absent & axon tracts are considerably lengthened in adult

Question 33

What would happen if neurogenesis could no longer occur in the hippocampus?

Answer 33

New events are limited by set of sparse codes provided by mature granulate cells in dentate gyrus
Dentate gyrus won’t have flexibility to encode new memories well or to interference between memories formed in hippocampus

Question 34

Why are older memories preserved?

Answer 34

They are presented by older neurons