Nerve Response to Injury Flashcards
Is nerve recovery possible in the PNS or CNS?
Nerve recovery is only possible in the PNS.
What happens to small and large neurons during injury?
Small neurons are likely to be totally destroyed, while large neurons may undergo destruction of the cell body and/or transection of the axon.
What occurs proximal to the site of axonal injury?
The axon reaction occurs, which may result in destruction of the cell body.
When does axon reaction appear after injury?
Axon reaction appears in the cell body 24-48 hours after the injury.
What changes occur in the cell body during axon reaction?
Nissl bodies disperse (central chromatolysis),
the nucleus assumes an eccentric position
the cell body swells.
What is Wallerian degeneration?
Wallerian degeneration is the degeneration of the axon distal to the site of transection.
What processes occur during Wallerian degeneration?
Axonal swelling and fragmentation, disintegration of the myelin sheath, and phagocytosis of axonal and myelin sheath debris occur.
What role do Schwann cells play in the PNS after injury?
In the PNS, Schwann cells proliferate and secrete nerve growth factor.
What is a glial scar?
A tangled mass formed by astrocytes extending longer and more numerous cytoplasmic processes.
How does phagocytosis of cell debris differ between CNS and PNS?
Phagocytosis of cell debris is a slow process in the CNS, much slower than in the PNS.
What is axonal sprouting?
Axonal sprouting is when surviving axons grow new branches that form synapses at the sites denervated by the original lesion.
What do Schwann cells form to support growing axons?
Schwann cells grow out to form a scaffold called Schwann tubes (bands of Bünger).
What is the axon recovery rate?
The axon recovery rate is 1 mm per day.
What is a limitation of regenerated fibers?
The diameter, length, and conduction velocity of a regenerated fiber is rarely better than 80% of the original.
which makes motor control less precise
What is a complication from axonal sprouting?
Axonal sprouts may enter Schwann tubes and attach to an incorrect target, so normal function does not return.
What is synkinesis?
Synkinesis refers to unintended muscle movements when these neurons fire.
What may cause phantom limb pain?
Stimulation of blindly ending sensory neurons may be one cause of phantom limb pain.
How is axonal regeneration limited in the CNS?
growth-inhibiting substances secreted by oligodendrocytes and astrocyte scar tissue.
What are possible recovery mechanisms in the CNS?
Recovery of function in the CNS occurs if other regions take over that function.
Cortical Maps and Cortical plasticity
Cortical maps can be modified by sensory input, experience, learning, and brain injury.
- Cortical plasticity and reorganization are likely mechanisms driving functional recovery after a stroke; reorganization can take years.
- Reorganization after a nerve injury may be a factor in some chronic pain syndromes.
What role do stem cells play after neurological injury?
Stem cells may be involved in brain remodeling following a neurological injury.
What happens to neural precursor cells after a stroke?
Neural precursor cells migrate toward the ischemic area after a stroke; many do not survive, possibly due to inflammation.
Where have neural stem cells been located?
Neural stem cells have been located in parts of the hippocampus and in cells lining the lateral ventricles.
Recovery of Synaptic Effectivness
- Edema that may occur after injury puts pressure on axons that may affect their normal functioning
- Reduction in edema can allow recovery
