The broken brain Flashcards
what does damage in the central nervous system cause?
irreversible changes to the structure of neurons
3 types of damage in the peripheral nervous system?
1.neurophaxia
2.axontomesis
3.neurotmesis
Neuropraxia
least severe, with no damage to axons or sheathing, often the result of stretching or compression
-demylineation
-reversible
-compression- myelin sheath is compacted
what happens if the soma of the cell is damaged
it cannot regenerate,
if the axon are damaged it can just grow it back
Axontomesis
moderate, axons damaged but sheathing intact
-dymelineation + axon lost but endonurim is entact meaning axon can grow back
Neurotmesis
most severe, partial or complete severance of axon and sheathing, likelihood of recovery dependant on type of cut (clean cut is better than twisted/ripped)
-dymelination and axon loss
-damage of endoneurium- there is a fear growth but not as well as if the endoneruium was enacted
-inolvement of perineurium if this is damaged -poor growth
-epineurium- damage in this there is no growth
Wallerian
degeneration of the distal portions of the axon and myelin after damage/compression
what do the 3 damages nerupaxia, axontomesis and neurotmesis lead to?
1.Wallerian
2.Axonal
Demyelination
axonal
progressive dying back of the neuron from distal to proximal regions
Demyelination
loss of oligodendroglial or Schwann cells
what is Transneuronal degeneration
describes the death of cells within the communication chain as they are no longer in use
what are the 2 types of transneruonal degeneration?
- anterograde (distal cells following the damaged cell)
2.retrograde degeneration (dying back of axons - axonal degeneration or death of cells proximal to the site of damage).
head trauma
nything that results in damage to the head that can lead to raised intracranial pressure and changes in consciousness
example of head trauma
nything that results in damage to the head that can lead to raised intracranial pressure and changes in consciousness
less-expanding lesions e.g abcsess, cysts, meningitis
Brain Haemorrhage
rupture of arteries or veins
how to detect haemorrhage?
CT imaging as fresh blood is bright compared to the grey tissue.
what are the different bleeds of different layers of meninges and brain tissue
Subarachnoid haemorrhage:
.
Extradural (epidural) haemorrhage)
Following a blow to the head, blood from torn meningeal arteries accumulates between the outer dural layer of the meninges and the skull.
Subarachnoid haemorrhage
This kind of bleed usually follows the rupture of a cerebral aneurysm (a balloon in the blood vessel that is a point of weakness). Blood collects in the CSF beneath the arachnoid layer of the meninges.
Subdural haemorrhage
Following a blow that causes the brain to move within the skull, e.g. in boxing, blood collects in the subdural space following the rupture of a vein.
Intracerebral/intraparenchymal haemorrhage
results from the rupture of a vessel within the brain tissue itself.
how does diffuse axonal injury impact lesions?
small lesions (areas of damage), usually at the border of the grey and white matter (this transition point between cell bodies and axons is a weak spot), but these lesions can have devastating effect
Diffuse axonal injury
damage that results from a twisting or rotational force being applied to the brain (e.g in a crash it’s rare to get a direct impact on the head, the head is more likely to rotate and turn on impact).
Concussion
form of mild traumatic brain injury (mTBI)
Contusion
bruises in the brain and tend to occur at more superficial levels of the cortex as the brain bumps during a traumatic event.
what are the 3 gradings of contusion?
1.mild:limited to the grey matter 2.moderate:involving grey and white matter
3.severe:haemorrhages coalesce
what are 2 indications of diffuse axonal injury?
1.scattered microhaemorrhages (small bleeds)
2.pockets of ischaemia in the white-grey matter border or in the white matter
Stroke
sudden onset of neurological symptoms due to either haemorrhage or ischaemia
acronym for identify someone is displaying stroke?
Face – has their face fallen on one side? Can they smile?
Arms – can they raise both arms and keep them there?
Speech – is their speech slurred?
Time to call 999 if you see any one of these signs
what are TIA in strokes and what are they caused by?
mini strokes
transient loss of blood supply, which resolve within 24 hours
- small tremors you get before a big earthquake, they are a warning sign that must be heeded.
what are the 4 brain regions used to confirm diagnosis?
1.Amyloid plaques
2.Neurofibrillary tangles
3.Inclusions
4.Prion proteins
Amyloid plaques
aggregations of misfolded/fragmented proteins found in the extracellular matrix
what are 3 different proteins in amyloid plaques?
1.β-amyloid (fragments of the amyloid precursor protein) in 2.Alzheimer’s Disease
3.α-synuclein (which mostly form fibrils) in Parkinson’s Disease
Prion proteins in Creutzfeldt Jakob Disease (CJD)
what amyloid plaques caused by?
protein phosphorylation, which leads to changes in protein folding and the formation of β-sheets
what do B sheets include?
sheet form insoluble fibres and toxic oligomers, which can clump together to form plaques
Neurofibrillary tangles
formed by the microtubule associated protein - Tau
what is Tau?
involved in the structural composition of microtubules which provide the transport system in a neuron
what does Hyperphosphorylation of tau lead to?
misfolding, which then causes the breakdown of the microtubules, β-sheet and fibril formation. These fibrils aggregate to form tangles
Inclusions
intracellular protein aggregations
what 2 things does inclusions lead to?
1.Lewy bodies
2.Pick cells
structure of inclusion?
-dense core of protein and a halo of surrounding filaments. The are the result of misfolded and ubiquitinated proteins
what other proteins can inclusion be made of?
1.ubiquitin
2.crystallin
3.neurofilament
what are inclusions made up of ?
α-synuclein
what role do prion protein play?
presynaptic transport and cell signalling (just like α-synuclein). Conformational changes as a result of changes in phosphorylation, leads to formation of β–sheets and fibrils