L20 Plasticity and Regeneration

Question 1

Inducing factors (determine gene expression I)

Answer 1

Signalling molecules from other cells, either:

• freely diffusible over long range,
• tethered to cell surface, acting locally

Question 2

Competence (determine gene expression II)

Answer 2

The ability of cell to respond to inducing factors, depends on:

• surface receptors
• transduction molecules
• transcription factors made by cell

Question 3

Define neurogenesis

Answer 3

the process by which neurons are generated

Question 4

What is the time period for neurogenesis

Answer 4

5th week – 5th month of gestation

Generates almost all neurones for life

Question 5

Neural Stem cells/precursor cells

Answer 5

1. Infinitely self –renewing
   Located in ventricular zone

After terminal division and differentiation, gives rise to full range of cell classes within the relevant tissue, e.g.
inhibitory
excitatory neurons
Glia cells

Question 6

Neural progenitor cell

Answer 6

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

Question 7

Protein distribution in precursor cells

Answer 7

Notch-1 protein on superior pole
Numb protein on inferior pole
Both differentially distributed in the precursor cells of the developing neocortex.

Vertical cleavage=identical neural stem cell/sister cell produced=equal proportion of proteins
Horizontal cleavage=different sister cells produced
-Notch-1 end=Neuroblast
-Numb end=Progenitor cell

Question 8

Neuroblast cell

Answer 8

Postmitotic, immature nerve cell differentiate into a neuron

Migrates to other parts of NS depending on

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

Question 9

Differentiation

Answer 9

Process by which structure becomes more functionally specialised during development

Due to specific spatiotemporal pattern of gene expression
.
INSIDE OUT DEVELOPMENT
-subplate forms scaffolding for many layers

3 steps for differentiation
-Pathway selection(select location)
-Target selection(select nucleus)
Address selection(select layer/position of tissue)

Question 10

Neuroblast differentiation

Answer 10

Growth cone: Extension of neurite

Filopodia: Allows neuroblast to navigate around environment

Question 11

Chemoattractant

Answer 11

E.g Netrin

• produced in ventral midline of spinal cord
• promotes growth of axon towards it

Question 12

Chemorepellant

Answer 12

E.g Slit

• secreted by midline cells
• Axons turn and extend away from it
• Robo receptor

Question 13

Neutrotrophic factors

Answer 13

Biomolecules that support the growth, survival and differentiation of neurones
E.g NGF

Question 14

Apoptosis and trophic interactions

Answer 14

Programmed cell death is the result of competition for trophic facts

allows productions of proper match in number of presynaptic and postsynaptic neurons.

Question 15

Synaptic elimination

Answer 15

Activity-dependent fine-tuning of neuronal connections.

Synaptic capacity

• Initially muscle fibre receives inputs from several alpha motor neurons.
• Gradually, all inputs but one are lost.

Selective loss of ACh
receptors
-blocking postsynaptic ACh can stimulate its loss
-Leads to withdrawal of axon branch

Question 16

The Critical Period Concept

Answer 16

Variable time window for different skills/behaviours

Two important factors for successful completion of the critical period:

1) Availability of appropriate influences
2) Neural capacity to respond to them

Question 17

Adult Neurogenesis

Answer 17

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