Regeneration regrowth of damaged neurons Reorganization Recovery Copyright 2006 by Allyn and Bacon Neuroplasticity and Responses to Nervous System Damage Both portions of the axon degenerate ID: 592159
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Degeneration - deteriorationRegeneration – regrowth of damaged neuronsReorganizationRecovery
Copyright © 2006 by Allyn and Bacon
Neuroplasticity
and Responses
to Nervous System DamageSlide2
Both portions of the axon degenerate
What happens when an axon is severed (cut)?Slide3
proximal portion of axon
distal portion of axonSlide4
Anterograde - degeneration of the axonal segment – between the cut and synaptic terminal
cut off from cell’s metabolic center- axonswells and breaks off within a few days
Copyright © 2006 by Allyn and Bacon
DegenerationSlide5
Anterograde degenerationSlide6
Retrograde degeneration– degeneration of the segment between the cut and cell body
takes place more slowlyif regenerating axon makes a new synaptic contact, the neuron may surviveSlide7
Anterograde degeneration
Retrograde degenerationSlide8
Regeneration is virtually nonexistent in the CNS of adult mammals and unlikely, but possible, in the PNS
Copyright © 2006 by Allyn and Bacon
Neural RegenerationSlide9
Only occurs at the proximal end of axonAxonal sprouting
What happens in the PNS? Slide10
Axonal sproutingSlide11
at the same time…..if myelin sheaths line up – they secrete “growth promoting” factors AND if one of the sprouts matches up – it will begin to grow and reestablish connectionsSlide12Slide13
differences in the glial cells that make myelinIn PNS – Schwann cells make myelin sheathsIn CNS –
oligodendroglia make myelin sheathsHOW THESE GLIAL CELLS DO THIS IS VERY DIFFERENT!!!Why doesn’t this happen in the CNS?Slide14
Schwann cell – each Schwann cell is a single segment of myelin
What are some of these differences?Slide15
Each of these is a Schwann CellsSlide16
Schwann cell – each Schwann cell is a single segment of myelinOligodendroglia – make multiple sheaths of myelin
What are some of these differences?Slide17Slide18
So the different ways they contribute myelin may make a difference
Also - Schwann cells promote regenerationby releasing neurotrophic factors (stimulate growth)
Oligodendroglia
- release “growth inhibiting” factors AND making it impossible for the axon to grow
Copyright © 2006 by Allyn and Bacon
Why do mammalian PNS neurons regenerate?Slide19
Can occur in the CNS
Reorganization Slide20
what are stem cells?derived from embryosmost are derived from embryos that develop from eggs that have been fertilized
in vitro (IVF) — in an in vitro fertilization clinic—and then donated for research purposes with informed consent of the donors. They are not derived from eggs fertilized in a woman's body.
pluripotent
- can develop into many cell types!
Role of embryonic stem cells Slide21
Two regions in the brain that we know this occursPart of the hippocampusSubventricular zone – area of lining of ventricles in brain
Controversy regarding the role of theseAdult stem cell neurogenesis