Plasticity and regeneration

Question 1

What determines gene expression in individual cells?

Answer 1

Inducing factors

Competence

Question 2

What are inducing factors?

Answer 2

Signalling molecules provided by other cells. They can be freely diffusible, exerting their action over a long range, or tethered together at the cell surface, acting locally.

Question 3

What do inducing factors do?

Answer 3

They can modify gene expression, cell shape and motility. Because cells in different positions in the embryo are exposed to different inducing factors, each cell’s position in early development is critical for its fate.

Question 4

What is competence?

Answer 4

The ability of a cell to respond to inducing factors,

Question 5

What does competence depend on?

Answer 5

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

Question 6

What is neurogenesis?

Answer 6

The process by which neurons are generated
5th week - 5th month gestation
Peak rate of 250000 new neurons/minute

Question 7

What are neural stem cells/neural precursor cells?

Answer 7

Infinitely self –renewing
After terminal division and differentiation they can give rise to the full range of cell classes within the relevant tissue, e.g. inhibitory and excitatory neurons, astrocytes, oligodendrocytes.

Question 8

What are neural progenitor cells?

Answer 8

Incapable of continuing self – renewal
Capable to give rise to only one class of differentiated progeny, e.g. an oligodendroglial progenitor cell will give rise to oligodendrocytes until its mitotic capacity is exhausted.

Question 9

What does the fate of the migrating neuron depend on?

Answer 9

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

Question 10

What is a neuroblast?

Answer 10

Postmitotic immature nerve cell that will differentiate into a neuron

Question 11

How does the cortex develop?

Answer 11

Inside out

Differentiation

Question 12

How does the neuroblast differentiate?

Answer 12

Growth cone and filopodia
Pathway selection
Target selection
Address selection

Question 13

What does apoptosis reflect?

Answer 13

reflects competition for trophic factors and produces the proper match in the number of presynaptic and postsynaptic neurons.

Question 14

Describe how brain circuits are modified

Answer 14

Modified as a result of experience
First steps in constructing brain circuitry rely largely on intrinsic cellular and molecular mechanisms (establishment of distinct brain regions, neurogenesis, major axon tracts, guidance of growing axons to appropriate targets, initiation of synaptogenesis).

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

Question 15

Describe the critical period concept

Answer 15

Variable time window for different skills/behaviours

e.g. sensorimotor skills, language acquisition, visual perception, emotional functions

Question 16

List two important factors for successful completion of the critical period:

Answer 16

Availability of appropriate influences (e.g. exposure to language, or species-specific songs for songbirds)
Neural capacity to respond to them

Question 17

What does development of visual perception require?

Answer 17

Sensory experience

Question 18

Why do critical periods end?

Answer 18

Various hypotheses (axon growth, synaptic transmission matures, constraint cortical activation)

Important for understanding recovery from damage

Question 19

Where does adult neurogenesis occur?

Answer 19

Sub Ventricular Zone (SVZ) to olfactory bulb
Hippocampus
primarily interneurons
some integrate in functional networks, but most die