Injury and the Potential for Recovery in the CNS Flashcards
List the different types of CNS injury.
- Developmental
- Traumatic - brain/spinal cord injury
- Ischaemic - e.g. stroke
- Hypoxic - e.g. cardiac arrest
- Inflammatory - e.g. multiple sclerosis
- Neurodegenerative conditions - e.g. Alzheimer’s, Parkinson’s
- Infection - e.g. meningitis, encephalitis
- Tumours
Describe the main features of stroke.
- Acute loss of blood supply damages the region supplied by the blocked artery.
- It takes 6-8 minutes of blood supply interruption (ischaemia) to cause neuronal death (infarction).
- Most cerebral vascular occlusions will reopen spontaneously within 24 hours, but neurons will be lost at a rate of 2 million per minute during this period.
Hypoxic brain injury affects which areas the most and why?
Grey matter: cerebral cortex, basal ganglia
These are the most metabolically active areas
Cerebral abscess with oedema and white lines in the sulci are suggestive of what?
- Cerebral abscess and oedema - infection
- White lines in sulci - meningitis specifically
What are the consequences of the death of an axon?
- Upstream - the cell body may die by apoptosis (retrograde degeneration)
- Downstream - the distal axon dies via Wallerian (anterograde) degeneration
Give an example of transneuronal degeneration in the visual system.
Damage to eye leads to degeneration of lateral geniculate nucleus (LGN) cells
Contrast the response to injury in the CNS and PNS.
PNS:
- Severed axons can regrow if their nerve sheath remains intact
- Macrophages clean up damaged cell parts - faster clean up aids regeneration
- Schwann cells assist in regeneration
CNS:
- Clean up is slow because the environment is not optimal
- Oligodendrocytes inhibit regeneration
What is the role of myelin in axon regeneration in the PNS?
- Provides a guide tube for the sprouting end of a severed neuron to grow through
- Extending axon guided to its destination as it is during development
Describe the features of glial scarring.
- Glial scarring/gliosis - proliferation of astrocytes and microglia after injury
- Protective mechanism and part of healing
- Beneficial and detrimental effects on injury
- Regenerates blood-brain-barrier after compromise and promotes revascularisation of injured brain
- Neuro-developmental inhibitors secreted by astrocytes prevent axon regrowth and regeneration
In the adult mammalian brain, significant neurogenesis only occurs in 2 areas. What are they?
- Hippocampus (dentate gyrus)
- Near lateral ventricles (subventricular zone)
- Both important for memory - perhaps memory “grows”
Everything we learn is hardcoded in the brain as a regional change in what?
Synaptic strength
Neurorehabilitation aims to promote which process?
Adaptive neural plasticity
Give an example of large-scale changes associated with neural plasticity.
Cortical remapping in response to injury
Name 3 ways in the which the brain can be repaired, other than neurogenesis.
- Compensation - one brain area takes over the functions damaged in another area
- Presynaptic neurons sprout more axon terminals - additional synapses and receptors formed
- Reorganisation - a more dramatic form of neural recovery, involving major brain areas
What are induced pluripotent stem cells (iPSC)?
- Stem cells produced by reprogramming mature adult cells
- Over-expression of 4 genes - Yamanaka factors - results in reprogramming
