Plasticity and regeneration

Question 1

What determines gene expression in individual cells?

Answer 1

Inducing factors

Competence

Question 2

Inducing factors

Answer 2

Signalling molecules provided by other cells

• freely diffusible, exerting their action over a long range
• tethered to the cell surface, acting locally

Question 3

Competence

Answer 3

The ability of a cell to respond to induing factors which depends on

• exact set of surface receptors
• transduction molecules
• transcription factors expressed by the cell

Question 4

Neurogenesis

Answer 4

Process by which neurones are generated

5th week to 5th month of gestation

Peak rate of 250,000 new neurones/ minute

Question 5

Neural stem cells/ neural precursor cells

Answer 5

Infinitely self-renewing

After terminal division and differentiation they can give risk to the full range of cell classes within the relevant tissue

Question 6

Neural progenitor cell

Answer 6

Incapable of continuing self-renewal

Capable to give rise to only one class of differentiated progeny

Question 7

Dividing precursor cells

Answer 7

1. In G1, nucleus is near ventricular surface
2. During S stage, nucleus and surrounding cytoplasm migrate toward the pial surface and DNA replicates
3. During G2, cell grows and nucleus migrates toward lumen again
4. In mitosis, cells lose connection to pial surface and divide, symmetrical divisions generate 2 neural stem cells, asymmetrical divisions generate neuroblast and progenitor cell

Question 8

Neuroblast

Answer 8

Postmitotic, immature nerve cell that will differentiate into a neurone

Fate of migrating neurone will be determined by

• age of precursor cell
• position in ventricular zone
• environment at time of division

Question 9

Neuroblast differentiation

Answer 9

1. Pathway selection
2. Target selection
3. Address selection

Question 10

Apoptosis or programmed cell death

Answer 10

Reflects competition for trophic factors and produces the proper match in the number of presynaptic and postsynaptic neurones

Question 11

Modification of brain circuits as a result of experience

Answer 11

First steps in constructing brain circuitry rely largely on intrinsic cellular and molecular mechanisms

Activity mediated influence on the developing brain is most consequential i early life, during temporal windows called critical periods

Question 12

The critical period concept

Answer 12

Variable time window for different skills/ behaviours

Two important factors for successful completion of the critical period

• availability of appropriate influences
• neural capacity to respond to them

Question 13

Adult neurogenesis

Answer 13

Sub ventricular zone to olfactory bulb

Hippocampus

• primarily interneurones
• some integrate in functional networks but most die