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