Injury and repair to the CNS Flashcards
What are 8 mechanisms of injury to the CNS?
Stroke (ishaemic), hypoxia, developmental, inflammatory, neurodegenerative, traumatic, infection, tumour.
What type of brain cells are affected by injury?
All- glial, neurons, blood brain barrier and CSF.
What is a craniectomy and the most common cause?
Where part of the skull is removed to give room for inflammation or oedema, therefore the swelling doesn’t affect the brain tissue.
What is a stroke?
an acute loss of blood supply that damages the region supplies by the blocked artery.
How long does it take for neuronal cells to die post ischaemia?
6-8 minutes.
How long does it normally take vascular occlusions to clear?
24 hours, they clear themselves. However too late at 2 million neurons die per minute in this time.
What is hypoxia brain injury? What areas does it affect most?
reduction of the whole brain oxygenation. Affects the most metabolically active areas (grey matter of cerebral cortex and basal ganglia.)
What is multiple sclerosis?
Disease where inflammation causes degeneration and neural dysfunction results
What happens to brain substance in neurodegenerative diseases?
whole brain substance shrinks. Neurons either get cut - Axotomy. or lose their normal input - denervation.
What are the consequences of axon death? (upstream and downstream)
Retrograde degeneration - cell body dies via apoptosis.
Anterograde degeneration. wallerian degeneration where the distal axon dies.
What is an important factor in the re growth of nerve cells?
Time - the longer it takes to clear dead cells the less chance of regrowth.
Why do cells in the PNS regrow but not in the CNS?
In the PNS severed axons regrow if their nerve sheath is intact.
Macrophages aid clear the damaged cells and create the optimal healing environment. Schwaan cells assist in regeneration.
In the CNS clean up of dead cells is slow and oligodendrocytes inhibit regeneration.
What is the role of myelin in the regeneration of nerve cells?
Provides a guide tube for the sprouting axon.
In development guides the sprouting axon to its destination.
What are the 5 classifications of nerve injury?
Grade 1 - neuropraxia.
Grade 2 - axonotmesis
Grade 3 - neurotmeses with preservation of perineurium
Grade 4 - neurotmesis with preservation of epineurium
Grade 5 - neurotmesis with complete transection of nerve trunk.
Outline grade 1 nerve injury.
Neuropraxia- conduction disruption. Intact axon and preserved supportive structures.
Outline grade 2 nerve injury.
Axonotmesis - disrupted axon with intact endoneurin - the delicate connective tissue surrounding the myelin sheath.
Outline grade 3 nerve injury.
Neurotmesis with preservation of perineurium. Disruption of the supporting structures. Perineurium is the sheath of connective tissue surrounding the fascicles of nerves. Endoneurium disrupted.
Outline grade 4 nerve injury
Neurotmesis with preservation of the epineurium. Epineurium is the outermost layer of dense irregular connective tissue surrounding peripheral nerves.
Outline grade 5 nerve injury.
Neurotmesis with complete transection of the nerve trunk
What is glial scarring?
Scars that form post CNS injury due to reactive proliferation of astrocytes and microglia.
How does glial scarring aid recovery?
regenerates a tissue barrier after blood brain barrier compromise and promotes revascularisation of the injured brain.
How does glial scarring prevent healing?
astrocytes secrete developmental inhibitors that prevent axon regrowth and regeneration.
What is neurogenesis? In an adult mammalian brain where is there evidence of this.
Birth of new neurons. Hippocampus and just below the lateral ventricles.
What is neurorehabilitation?
As brain injuries are irreversible there is a focus on treatment - with restoration and maximisation of loss of function. Involves learning which will change synaptic strength in different regions of the brain.
