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35 Cards in this Set

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  • Back
What are the 3 options for what nervous system cells can do in response to injury?
1. Cell death
2. Cell injury and dysfunction
What happens when Glia die?
Other glia proliferate and take their place
What happens when neurons die?
We think they don't come back but it's not for sure..
Can neurons be cultured from adult CNS tissue?
Is neuron regeneration a way to recover from injury?
No; but it may be able to improve function.
What does the fact that newly differentiated neurons can be cultured from an adult CNS suggest?
The presence of a NEURONAL STEM CELL population
What did the BrdU study find?
That when they put bromodeoxyuridine into the brains of terminal cancer patients, their harvested brains had new neurons in them.
When the CNS is injured, what happens if the cell doesn't die?
Its cell body or dendrites recover
What is the most significant consequence of neuronal injury?
Interruption of conduction along axons.
What are 2 types of injury that interrupt axon conduction?
1. Demyelination and conduction block
2. Axotomy
What are the 3 things that happen in the course of Axotomy?
1. Prox/distal stumps don't reconnect
2. Distal stump degenerates
3. Proximal stump is sustained by the cell body
What is it called when the distal stump degenerates?
Wallerian degeneration
What are 2 proximal changes seen after axotomy?
1. Proximal stump withdrawal
2. Cell body chromatolysis
What is chromatolysis?
The movement of Nissl substance to the cell body periphery plus a reduction in RER
Why is chromatolysis seen in axotomy?
Because the cell switches from making membrane proteins to soluble proteins
If the neuron survives an axotomy, what changes happen after a time of proximal stump withdrawal?
It will sprout growth cones
What do the elongating neurite sprouts from the proximal stump do?
Look for a place to go - the distal stump!
What cells aid in the sprouting neurites entering the distal stump?
Schwann cells remaining within basal lamina tubes of the neurons.
What are the schwann cells that remain within the basal lamina tubes called?
Bands of Bungner
What happens to this type of axon regeneration when a gun shot wound severely disrupts the axon sheath?
The wandering neurite sprouts instead can form a neuroma which is quite painful when touched.
In what part of the nervous system can this axon regeneration occur?
PNS - not in the CNS!
What are the 2 dichotomies to axon regeneration after injury?
1. Developmental - it can happen in CNS in fetuses/young animals
2. Anatomical - PNS regeneration can occur thruout life, not in the CNS.
Why can axon regeneration occur in early development?
Because there is a more supportive environment and more plasticity
Why can't the CNS regenerate axons later in life?
We don't know
Is it the neuron or the environment's fault?
Not the neuron's fault!
What happened when people cut a sciatic nerve proximally and tied it off to prevent regeneration of axons into distal stumps, and 2 wks later grafted it onto an optic nerve?
The CNS grew axons out to the graft and continued to elongate to the end of the graft!
So what do we see from this experiment?
CNS axons CAN regenerate and form functional synapses with target areas.
What allowed this CNS regeneration?
The permissive environment of the CNS sciatic axon being in the peripheral nervous system.
So what is the inhibitory factor that prevents CNS regeneration maybe?
The CNS environment
What is it about transection in the PNS that makes nerves able to regenerate?
They keep their Schwann cells within the basement membrane and form those Bands of Bunggner
How can we promote peripheral nerve regeneration in the PNS?
By using polymer coated tubes that act like the nice warm straight tubes with bands of bunggner
What's so bad about the CNS?
Oligodendrocytes - it's the damn glia
What promotes CNS regeneration?
Antibody that masks the glial factors produced from oligodendrocytes
What is Nogo
The oligodendrocyte protein that shuts down axon growth!
Will we see CNS regeneration in our lifetime?