Regeneration and Repair Flashcards
Does Neurogenesis occur during embryonic stages only?
Neurogenesis was initially thought to occur only during embryonic stages, however it occurs in adulthood as well
What is Regeneration?
is ability to repair itself following injury
regeneration is the body’s process of restoring or replacing cells or organs that are damaged or lost following injury.
Most living organisms, especially the complex ones have some capacity to regenerate or be limited. the more complex the animals, the more limited.
How does Adult neurogenesis occur?
is the formation of functional, mature neurons from neural stem cells in specific brain regions in adults.
Two areas where neurogenesis occur is in the subventricular zone (SVZ) and subgranular zone (SGZ) – maintain a pool of self-renewing cells. The
most active area of neurogenesis is the hippocampus In these regions, new neurons are generated throughout life and integrated into established neuronal circuits.
neurogenesis -
the production of new neuronal cells from
precursor populations that subsequently produce neurites to
make connections with host cells
Where is the most active area of neurogenesis?
Two areas where neurogenesis occur is in the subventricular zone (SVZ) and subgranular zone (SGZ) – maintain a pool of self-renewing cells. The
most active area of neurogenesis is the hippocampus
What is the life-span of the new neurons generated in the hippocampus?
Thousands of new cells are produced in the hippocampus each day, although many die within weeks of their birth. Some of these new
neurons survive and integrate themselves into the working brain. The more the animal learned, the more neurons survive in the hippocampus.
Restoration of brain function following neuronal
damage can occur by:
Neurogenesis
Axonogenesis
rewiring
axonogenesis
- axon regrowth from injured neurons in the peripheral
nervous system through the injury site to re-establish
connections **
**NB: Mammalian CNS axons tend not reinnervate because of factors secreted by
oligodendroglia cells that inhibit growth. Nogo which is released when
oligodendroglia cells are damaged.
rewiring
– new connections are formed to replace ones that
are damaged to re-establish function of the neural pathway
Restoration of brain function using the visual system as an example:
the regenerative capacity of the retinal ganglion cells, and the visual system is well known
However significant barriers still remain which block the re-establishment of connectivity to restore visual function following traumatic injury or disease induced degeneration.
The retinal ganglion cells damage
The retinal ganglion cells (RGCs) are the output cells of the retina into the brain. In mammals, these cells are not able to regenerate their axons after optic nerve injury, leaving the patients with optic neuropathies with permanent visual loss.
What is the ability of retinal ganglion cells to generate axons and make connection is dependent on?
the ability of the cells to generate axons and go out of the eye and into the optic nerve is highly dependent on the production of a range of factors, such as transcription and growth factors.
if these factors are not produced the retinal ganglion cell dies in the optic nerve itself. supportive glial cells may not be present, especially in the adult and inhibitory influences also associated with the scar can block regenerative capacity of the nerve itself at the optic chiasm . growth cones, which modulate the growth of the new, new axon can be miss-routed toward other areas of the brain, or hole completely. Blocking the optic nerve from regenerating in the target region of the lateral geniculate nucleus, as well as the superior colliculus. Although the axons are guided to these targets’ synapse may form in the wrong retinotopic area. Synapse strength may also be inappropriate to mediate functional connectivity.
Regeneration of CNS
Regeneration of CNS requires progenitor cells to migrate, re-establish cell contacts, self-renew and undergo specification and spatial
patterning to form neurons and glia that will integrate into host tissue to
replace the damaged structure.
Totipotent stem cells:
Cells able to give rise to all embryonic somatic cells and germ cells. They can build a whole animal. The zygote and a few early cells of the morula are totipotent.
Pluripotent stem cells:
These cells are descendants of totipotent stem cells and can give rise to cells of the three germ layers: endoderm, mesoderm, and ectoderm.
