Download 6-8_TissueDamageRegen_SteinÁN

Stein Ágnes Noémi
Tissue damage and tendency for regeneration in the PNS and CNS
1. Neurodegeneration
Neurodegeneration is the umbrella term for the progressive loss of structure or function of neurons,
including death of neurons.
This deterioration gradually causes a loss of cognitive abilities such as memory and decision making.
There are lot of neurodegenerative diseases, for example:
 Alzheimer’s disease (AD) and other dementias
 Parkinson’s disease (PD) and PD-related disorders
 Prion disease
 Motor neurone diseases (MND)
 Huntington’s Disease (HD)
Neurodegenerative diseases are caused by genetic mutations, traumatic brain injury, tumor, infection,
oxidative stress, chemical damage, ischemia and hypoxia.
2. Damage and regeneration in the PNS
Neuroregeneration differs between the peripheral nervous system (PNS) and the central nervous
system (CNS) by the functional mechanisms and especially the extent and speed. When an axon is
damaged, the distal segment undergoes Wallerian degeneration, losing its myelin sheath. The proximal
segment can either die by apoptosis or undergo the chromatolytic reaction, which is an attempt at
repair.
In PNS axonal sprouts form at the proximal stump and grow until they enter the distal stump. Injury to
the peripheral nervous system immediately elicits the migration of phagocytes, Schwann cells,
and macrophages to the lesion site in order to clear away debris such as damaged tissue. After injury,
the proximal end swells and it begins to sprout axons. The proximal axons are able to regrow as long
as the cell body is intact, and they have made contact with the Schwann cells.
3. Damage and regeneration in the CNS
In contrast with peripheral nervous system injury, injury to the central nervous system is not followed
by extensive regeneration. It is limited by the inhibitory influences of the glial
and extracellular environment. Slower degeneration of the distal segment contributes to the inhibitory
environment; inhibitory myelin and axonal debris are not cleared away as quickly. All these factors
contribute to the formation of what is known as a glial scar, which axons cannot grow across.
Sources:
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http://www.medicalnewstoday.com/articles/246847.php
http://onlinelibrary.wiley.com/doi/10.1111/j.1582-4934.2001.tb00134.x/epdf
http://www.chemonet.hu/osztaly/kemia/penke.html
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2846285/
https://ntp.neuroscience.wisc.edu/neuro670/reqreading/RegeneratingTheNervousSystem.pdf
http://humanphysiology.academy/Neurosciences%202015/Chapter%201/P.1.1.4%20Nerve%20Regeneration.html