Denervation and Regeneration Flashcards
What is Wallerian Degeneration?
Injury of a motor neuron axon that causes
1) degeneration of the distal axon
2) proliferation of Schwann cells
3) swelling of nucleus
4) Dispersion of ER
When postsynaptic neuron is damaged, what happens in presynaptic cell?
1) retraction of presynaptic terminals
2) residual synapses release less transmitter
What happens to presynaptic cell if damaged postsynaptic cell recovers?
Synaptic inputs will recover
What happens to denervated muscle?
Muscle becomes more sensitive to acetylcholine because we have increased synthesis of AChR in adjacent areas
What happens to denervated muscle if it is stimulated?
Sensitivity in extrasynaptic regions goes down. Sensitivity in synaptic regions is high.
What influences AChR expression in synaptic areas? Extrasynaptic areas?
agrin stimulates AChR expression; electrical activity suppresses via Ca-signaling
If axon is cut and degraded, what can neighboring axons do?
They can do axonal sprouting where they make branches to the muscle the 1st axon was connected to and innervate it instead.
What are regenerating axons guided by?
endoneurial tubes of the former axons to the original sites on the muscle
What does regenerative capacity of the nervous system depend on?
A) species
B) developmental time periods
C) parts of the nervous system
What species tend to have higher regenerative capacity
invertebrates and lower vertebrates
What developmental time periods tend to have higher regenerative capacity?
fetal and neonatal phase
What parts of the nervous system tend to have a higher regenerative capacity?
PNS (peripheral nervous system)
Why is regeneration better in vertebrate PNS?
They have schwann cell that start to proliferate produce trophic factors (BDNF, NGF), extracellular matrix proteins, and cell adhesion proteins
How do schwann cells proliferate?
Macrophages come to injury site, release cytokines (LIF), and cause proliferation of Schwann cells. BDNF and NGF help axon to regenerate
What are ways to kill muscle fibers in NMJ? What happens after you kill it
cutting or cold metal will kill the muscle fiber. If motor neuron doesn’t die, schwann cells remain, and you have myoblasts in the area, the muscle fiber will regenerate
