Plasticity and regeneration

Question 1

Inducing factors that determines gene expression

Answer 1

Signalling molecules from other cells, either:

• Diffusible, over long range
• On cell surface, locally

Question 2

Competence in gene expression

Answer 2

The ability for cell to respond to inducing factors

Depends on:

• Set of receptors on cell
• Transduction molecules
• Transcription factors made by the cell.

Question 3

Time period for neurogenesis

Answer 3

5th week- 5th month of gestation

Generates almost all neurones for life

Question 4

Neural stem cells/ precursor cells

Answer 4

Infinitely self-renewing cells of NS
- Located in ventricular zone

Gives rise to range of cell classes within relevant tissue, after terminal division and differentiation

• Inhibitory
• Excitatory
• Glia cells

Question 5

Neural progenitor cell

Answer 5

Cells of NS incapable of self-renewal

Can only give rise to one class of differentiated progeny cells
- E.g oligodendroglial progenitor can only give rise to oligodendrocytes

Question 6

Protein distribution in precursor neural cells

Answer 6

Notch-1 protein= superior pole
Numb protein= inferior pole
- Both distributed differently in precursor cells of developing neocortex

Vertical cleavage of cell= identical sister cell produced
- equal proportion of proteins

Horizontal cleavage= different sister cells produced

• Neuroblast [Notch-1 end]
• Progenitor cell [Numb end]

Question 7

Neuroblast

Answer 7

Post-mitotic, immature nerve cell that differentiates into a neurone
- Migrates to other parts of NS

Question 8

Factors that determine what happens to a migrating neurone

Answer 8

Age of the neural stem cell

Position of ventricular zone

Environment at the time of cell division

Question 9

Differentiation

Answer 9

Process of when tissues become more specialised during development

• Due to specific spatiotemporal pattern of gene expression
• Inside out development
• Subplate forms scaffolding for many layers

Three steps:

• Pathway selection [select the location]
• Target selection [select the nucleus]
• Address selection [select layer/ position in tissue]

Question 10

Neuroblast differentiation

Answer 10

Growth cone:
Extension of neurite

Filopodia:
Allows neuroblast to navigate around environemnt

Question 11

Netrin

Answer 11

Chemoattractant

• Produced in ventral midline of spinal cord
• Promotes growth of axons towards it

Question 12

Slit

Answer 12

Chemorepellent secreted by midline cells

• Axons turn and extend away from it
• Robo receptor

Question 13

Contact-mediated attraction and repulsion

Answer 13

Guidance cue for neuronal growth

Attraction
- Axons come across substrate bound ones and extend along their cell surface

Repulsion
- Axons come across substrate bound ones and retract growth cones

Question 14

Neurotrophic factors

Answer 14

Biomolecules that support the growth, survival, and differentiation of neurons.

Example
- Nerve growth factor

Question 15

Apoptosis and tropic interactions

Answer 15

Programmed cell death is the result of competition for tropic factors

Allows the production for the correct match of presynaptic to post synaptic neurones.

Question 16

Synaptic elimination

Answer 16

Method of fine-tuning for neuronal connections [e.g at neuromuscular junction]
- Activity dependant

Synaptic capacity

• At first muscle fibre would receive input from many alpha motor neurones
• Overtime in develop, all but one input is lost

Selective loss of AcH receptors

• Blocking postsynaptic AcHr can stimulate its loss
• Leads to withdrawal of axon branch

Question 17

Critical period

Answer 17

Temporal window for different skills and behaviours

• Sensorimotor skills
• Language acquisition etc

Factors that determine its successful completion:
1. The availability of appropriate influences

2. Neural capacity to respond to those influences

Question 18

Visual perception and sensory experience

Answer 18

Sensory experience is required for visual perception.

Study with ocular dominance columns by Hubel and Wiesel showed:

• 3-6 days monocular deprivation [early after birth] in a baby animal led to ipsilateral vision
• Does not occur in adult animals

Question 19

Visual deprivation + ocular dominance

Answer 19

Monocular deprivation in critical period led to alternating ocular dominance columns becoming unequal

• Deprived eye column shrinks
• Non-deprived eye column thickens

Question 20

Hebbian modifications during development

Answer 20

Process that strengthens synapses.

At first inputs fire out of sync into a cell
- Loses its synapses during developing [out of sync]

Inputs in sync undergo Hebbian modification to become more effective

Question 21

Plasticity in adult cerebral cortex

Answer 21

Functional changes in part of a tissue occur in relation to motor and sensory experience

Example:
- Amputation of the third digit saw cortex responding to digit 3, merged to respond to digit 3 and 4/

Question 22

Peripheral nerve regeneration

Answer 22

1. Macrophages remove myelin debris from injured peripheral nerve.
2. Growth related genes are expressed in soma which stimulates production of:
   - Axon growth promoting signals
   - Neutrophins
3. Proliferating Schwann cells promote axon regeneration

Question 23

Central nerve regeneration

Answer 23

1. Microglia clears myelin debris from damaged axon.
2. Astrocytes, oligodendrocytes and microglia locally produce inhibitory factors
3. Glial scar forms

Question 24

Adult neurogenesis

Answer 24

Only occurs:
- subventricular zone–> olfactory bulb

• Hippocampus

Question 25

Subventricular zone

Answer 25

Located in the wall of lateral ventricle

Type A cells- close ependymal layer

B cells- Form astrocytic ribbon

C cells- Located close to myelin and striatum

Question 26

Subventricular zone in Huntington’s disease

Answer 26

Loss of striatal cells

Thicker SVZ
- More A, B and C cells

Rich with endogenous mitogenic factors

• Neuropeptide Y
• Nitric oxide synthase
• GABAr subunits
• Cannaboid receptor

Question 27

Subventricular zone in Parkinson’s disease

Answer 27

Death of D2/3 C cells
- Due to reduced dopamine input from substantial nigra

Fewer progenitor cells

Question 28

Subventricular zone in Alzheimer’s disease

Answer 28

Imbalanced ratio of secreatases

• Accumulation of amyloid
• Reduces neurogenesis
• Induces generic cell death

Question 29

Dividing precursor cell

Answer 29

G1- Nucleus is near ventricular surface

S1- nucleus and cytoplasm migrate to pial surface for DNA replication

g2- Cell grows and nucleus migrates towards ventricular surface

Mitosis- Cell loses connection to pial surface—-> divide

Question 30

Imprinting

Answer 30

Develops social interaction in humans vital for normal development.