PSY2061 Chapter Notes - Chapter 10: Oligodendrocyte, Neurotrophic Factors, Encephalitis
5 Jun 2018
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PSY2061 – Readings – Week 7
• study of the human brain damage serves two purposes - it increases our
understanding of the healthy brain and it serves as a basis for the
development of new treatments
• causes of brain damage
•
o brain tumours
o
▪ a tumor or neoplasm is a mass of cells that grow
independently of the rest of the body
▪ about 20% of tumours found in the human brain are
meningiomas - tumour that form between the meninges -
the three membranes that cover the central nervous
system
▪
▪ all meningiomas are encapsulated tumours -
tumours that grow within their own membrane -
easy to identify on a CT scan
▪ influence the function of the brain only by the
pressure they exert on surrounding tissue - they are
almost always benign tumours - tumours that are
surgically removable with little risk of further
growth in the body
▪ most brain tumours are infiltrating - besides meningiomas
▪
▪ infiltrating tumours are those that grow diffusely
through surrounding tissue
▪ they are usually malignant tumours - difficult to
remove or destroy them completely - and any
cancerous tissue that remains after surgery
continues to grow
▪ gliomas - brain tumour that develop from glial cells -
are infiltrating, rapidly growing and common
▪ about 10% of brain tumours do not originate in the brain
▪
▪ they grow from infiltrating cells that are carried to
the brain by the bloodstream from some other part
of the body
▪ these are called metastatic tumours
▪ many originate as cancers of the lungs
▪ acoustic neuromas - tumours that grow on nerves or tracts
o cerebrovascular disorders - strokes
o
▪ strokes are sudden-onset cerebrovascular disorders that
cause brain damage
▪ the symptoms of a stroke depend on the area of the brain
affected - but common consequences of stroke are amnesia,
aphasia - language difficulties, paralysis and coma
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▪ infarct - the area of dead or dying tissue produced by a
stroke
▪ penumbra - surrounding the infarct - a dysfunctional area -
may recover or die in the ensuing days
▪ there are two major types of strokes - those resulting from
cerebral haemorrhage and those resulting from cerebral
ischemica
▪
▪ cerebral haemorrhage
▪
▪ bleeding in the brain
▪ occurs when a cerebral blood vessel ruptures
and blood seeps into the surrounding neural
tissues and damages it
▪ bursting aneurysms are a common cause of
intracerebral haemorrhage
▪
▪ an aneurysm is a pathological balloon
like dilation that forms in the wall of
an artery at a point where elasticity of
the artery wall is defective
▪ aneurysms can occur in any part of the
body
▪ can be congenital - present at birth
▪ or can result from exposure to
vascular poisons or infection
▪ cerebral ischemia
▪
▪ the disruption of blood supply to an area of
the brain
▪ three main causes
▪
▪ thrombosis
▪
▪ a plug called thrombus is
formed and blocks blood flow
at the site of formation
▪
▪ a thrombus may be
composed of a blood
clot, fat, oil an air
bubble, tumour cells or
a combination
▪ embolism
▪
▪ also a plug - called an embolus -
carried by the blood from a
larger vessel - becomes lodged
▪ arteriosclerosis
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find more resources at oneclass.com
▪
▪ walls of blood vessels thicken
and the channels narrow -
usually as a result of fat
deposits
▪ this can eventually lead to
complete blockage of the blood
vessels
▪ takes a while to develop
▪ does not occur equally in all parts of the brain
- particularly susceptible are neurons in
certain areas of the hippocampus
▪ glutamate - plays a major role in ischemia
induced brain damage
▪
▪ after a blood vessel becomes blocked -
many of the blood deprived neurons
become overactive and release
excessive quantities of glutamate -
then over activates glutamate
receptors in the membranes of
postsynaptic neurons - receptors most
involved - NMDA - N-methyl-D-
asparate receptors
▪ resulting in a large number of Na+ and
Ca2+ ions in the postsynaptic neurons
▪
▪ this trigger the release of
excessive amounts of glutamate
from the neurons - spreading
the toxic cascade - trigger a
sequence of internal reactions
that kill the postsynaptic
neurons
•
o closed head injuries
o
▪ brain injuries produced by blows that do not penetrate the
skull
▪ contusions
▪
▪ closed head injuries that involve damage to the
cerebral circulatory system,
▪ this damage produces internal hemorrhaging -
which results in hematoma
▪
▪ a hematoma is a localised collection of clotted
blood in an organ or tissue - a bruise
find more resources at oneclass.com
find more resources at oneclass.com
