neuroplasticity

Question 1

what is plasticity?

Answer 1

capacity for neuronal change

Question 2

4 main neuroplastic responses?

Answer 2

1) degeneration
2) regeneration
3) reorganisation
4) recovery

Question 3

neural degeneration: types

Answer 3

• Anterograde deterioration: deg of the distal segment (by synaptic terminals) (quicker)
• Retrograde deterioration: deg of the proximal segment (closer to cell body) (gradual)
• transneuronal degeneration: when degeneration spreads to neurons linked via synapses

Question 4

retrograde deterioration can change the cell body

Answer 4

Can be:
Degenerative –> decrease in size leading to autopsis
Regenerative –> increase in size indicates that the cell body is making proteins to replace those lost in degen BUT DOESNT mean it’ll SURVIVE

Question 5

types of transneuronal degeneration

Answer 5

• Anterograde transneuronal degen: when degen spreads from damaged neuron to neuron ON WHICH they synapse:
• Retrograde TND: spreads to neurons that synapse ON THEM

Question 6

where is neuronal regeneration virtually non existent?

Answer 6

CNS

Question 7

axon regrowth can occur in 3 different ways

Answer 7

1) schwann cell guidance
2) medium sized gap between the halves
3) overly large gap between the halves

Question 8

axon growth in PNS using Schwann cells in small gap

Answer 8

if original schwann cells are intact, the axon will grow through the original sheath to their correct/ORIGINAL targets

Question 9

axon growth in PNS when the gap is mediocre in size

Answer 9

the axons may end up reforming and connecting with the wrong alternate half (incorrect axons –> incorrect sheath –> incorrect destination)

Question 10

axon regeneration in PNS when the gap is widely separated

Answer 10

the axons may become tangled around the proximal stump & die

Question 11

what is it in the PNS system that allows the axons to regenerate?

Answer 11

Schwann cells (only in PNS)

Question 12

Purpose of schwann cells

Answer 12

clear debris resulting from degeneration & promote regeneration

Question 13

how do schwann cells promote regeneration?

Answer 13

• neurotrophic factors: proteins released that stimulate growth of axons
• Cell adhesion molecules: mark the paths that the PNS axons can take to grow

Question 14

CNS equivalent to PNS schwann cells?

Answer 14

Oligodendroglia (aka oligodendrocytes)

Question 15

what do oligodendroglia do?

Answer 15

• actively block regeneration (Yiu & He 2006)

- survive much longer after the nerve damage (Vargas & Barres, 2004)

Question 16

what is the function of oligodendroglia? (2)

Answer 16

1) support & insulate axons in CNS

2) create the myelin sheath - essential for control & electrical charge

Question 17

collateral sprouting - what?

Answer 17

• when axons grow out from healthy neurons & take up the now empty sites of degenerated neurons
• can grow out from terminals & nodes of ranvier

Question 18

mechanisms of neural reorganisation (5)

Answer 18

1) strengthening of existing connections through release of inhibition
2) collateral sprouting
3) adjustment of dendritic trees
4) adult neurogenisis
5) training in non- affected area

Question 19

neural reorganisation –> strengthening of existing connections through release of inhibition

Answer 19

evidence in support:

• reorganisation occurs too quickly to be explained by neural growth
• rapid reorganisation never covers extensive surface

Question 20

neural reorganisation –> collateral sprouting

Answer 20

evidence in support:

- magnitude of long term reorganisation is too great to be explained by strengthening of current neurons

Question 21

neural reorganisation –> adjustment of dendritic trees

Answer 21

make more links & connections (Wilson, 2007)

Question 22

neural reorganisation –>adult neurogenisis

Answer 22

• process of generating new neurons which integrate into existing circuits as an adult
• only really occurs in olfactory bulb & hippocampus

Question 23

neural reorganisation –> training

Answer 23

Nudo (2013)

- training will help functions to return

Question 24

recovery of function is hard to study bc there are other compensatory mechanisms which may be confused with plasticity (3)

Answer 24

1) cerebral edema: swelling in brain; if reduces in a few week may seem like recovery of function
2) learning of new cog & beh strategies: may dev new ways to do a task; subst of function > return of lost function
3) cognitive reserve: intelligence & education

Question 25

neuroplastic responses to recovery

Answer 25

1) Nishimura et al. (2007) show that neurop changes to undamaged areas have contributed to recovery after CNS damage
2) adult neurogenesis (Zhal et al. 2003) & stem cell creation in hippocampus
~~~BUT isnt evidence to support the long distance travelling of stem cells

Question 26

treatment of neuronal damage: 4

Answer 26

1) promoting regeneration
2) blocking neurodegeneration
3) neurotransplantation
4) rehabilitation

Question 27

promoting regeneration

Answer 27

a) eliminate inhibition from oligodendroglia
b) provide schwann cells to direct growth (Cheng, cao & olsen 2006)
c) transplanting olfactory ensheathing cells (raisman & Li 2007)

Question 28

blocking neurodegeneration

Answer 28

a) autopsis inhibitor protein
b) nerve growth factor: promotes growth over degeneration (sofroniew et al. 2001)
c) estrogens: limit death & decay

Question 29

neurotransplantation

Answer 29

a) FETAL TISSUE: big debate on use (dunnett, Bjorklund & Lindrall 2001)
b) STEM CELLS: mulitpotent
more research needed (Li et al. 2008)

Question 30

rehabilitation

Answer 30

• constraint induced therapy ( Taub et al 2002)

- facilitated walking to treat spinal injury (wolpaw & Tennissen 2001)