Neural repair and plasticity

Question 1

Can axonal repair occur in CNS? PNS? Can neuron replacement occur in the CNS? PNS?

Answer 1

Axonal repair can only occur in the PNS

If a neuron dies, it is not replaced

Question 2

What happens when transection of an axon occurs in the CNS? What mediates (protein) reactive gliosis?

Answer 2

Astrocytes undergo reactive gliosis which walls off the site of injury. This prevents axonal regeneration from happening

glial fibrillary acidic protein (GFAP)

Question 3

can you test for reactive gliosis present?

Answer 3

yes

You can stain for GFAP

Question 4

What happens when transection of an axon occurs in the PNS?

Answer 4

transection of an axon in the PNS results in Wallerian degeneration - axon distal to the site of injury degenerates. Schwann cells proliferate and remove the dibris of the distal axon. Schwann cells then grow a scaffold for the axon to grow through

Question 5

What 2 extrinsic factors promote axonal regeneration in the PNS?

Answer 5

nerve growth factor (NGF)

brain-derived neurotrophic factor (BDNF)

Question 6

what is the rate of axon regeneration?

Answer 6

1mm/day

Question 7

Why does reactive gliosis occur?

Answer 7

it walls off the site of damage, but more importantly fills in the empty space as the CNS needs a structure/scaffolding for support

Question 8

Describe plasticity at the neuron level (2 types)

Answer 8

short term: increased neuronal firing and increase in post-synaptic receptors to strengthen synapse

Long term: creation of collaterals that increase the strength of synapse

Question 9

Describe neuroplasticity of a microcircuit

Answer 9

If a damaged neuron can no longer perform its function (it dies), a microcircuit is rewired so that axons with similar functions take over the fucntion/response of the lost neuron

Question 10

describe neuroplasticity at the cortical level

Answer 10

the loss of a limb or stroke to a certain region of the brain results in remapping of functions