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Chapter 14

PSYB65 - Chapter 14 - Sep 20-Oct 4, 2010


Department
Psychology
Course Code
PSYB65H3
Professor
Ted Petit
Chapter
14

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Chapter 14 Human Brain Damage
Module 14.1: Causes of Brain Damage
Tumors (Neoplasms)
-Tumor: mass of new and abnormal tissue that is not physiologically beneficial to its
surrounding structure.
Describe tumors as space-occupying lesions (= they are foreign objects that cause
damage to the central nervous system (CNS) by putting pressure on it and occupying space
that is normally occupied by the CNS.
Differ from one another (what type of cell give rise to tumor, how rapidly they grow,
whether they infiltrate and destroy the surrounding neural tissue or remain relatively
encapsulated, and how likely they are to recur if they are removed)
-4 major types of brain tumors: those that originate from glial cells, the meninges, nervous
tissue, or other parts of the body already infected with a tumor
Tumors arising from glial cells (most common type)
-Gliomas - tumors that arise from glial cells
Astrocytomas
(arise from the growth of
astrocytes)
Glioblastoma Medulloblastoma
(also called a primitive
neuroectodermal tumor)
Major type Major type Less common
Tend not to grow very quicklyGrow quickly
Are rarely malignantHighly malignant Highly malignant infiltrating
tumor
-Some astrocytomas are
relatively well
encapsulated, so the
damage that they cause
tends to come from
compression of the
surrounding tissues
-Slow-growing benign
tumors can be extremely
dangerous if they start to
grow in relatively
inaccessible locations.
-Tend to infiltrate the
surrounding tissues,
making them very difficult
to excise surgically
without the removal of the
relatively healthy
surrounding neural tissue
-Tend to form around the
cerebellum and brainstem
early in life
-Prognosis for individuals
who develop
Medulloblastoma tends to
be relatively poor
When surgical treatment is not
practical, Chemotherapy is
typically used
Chemotherapy Chemotherapy
Tumors arising from the Meninges
-Meningiomas – tumors that grow out of (and remain attacched to) the meninges
Because they grow out of tissues found outside of the CNS, meningiomas tend to be
reasonably well encapsulated.
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Harmful effects tend to result from pressure applied at the site of the tumor as well as
sites distal from the tumor.
Surgery is the best treatment.
-When the tumor is located in a relatively inaccessiable part of the brain for surgery
Chemotherapy or radiotherapy is used as a treatment.
Metastatic tumors (Metastases) - secondary tumors that form from migrated tumor tissue.
-More common for the original tumor to be located outside of the CNS
-Simple metastatic tumors - only one tumor forms at one side.
Surgical or radiological treatment
-Multiple metastatic tumors - usually spreading from the lungs to the CNS.
Whole-brain radiotherapy or chemotherapy (most common), but prognosis is quite poor.
Neuropsychological effects of tumors
-The behavioural symptoms that arise from the formation of a tumor vary widely, just as the
size, location, cell type, and growth rate of the tumors varies.
E.g. located near the primary visual cortex - cause blindness
-To the brain damage caused by infiltration and compression, tumors can cause epileptic
seizures and release substances that are toxic to the brain.
Cerebrovastular Disorders
-Cerebrovascular disorder (stroke) - when the blood supply to the brain is interrupted (can be
sudden/gradual, complete/relative, permanent/transient)
-Cerebrovascular accident (CVA) - a class of cerebrovascular disorders, which result in
interruptions to the brain's blood supply.
Results in cerebral ischemia (lack of blood supply to the brain). If the cerebral ischemia
is severe or long-lasting enough to kill neurons, the damaged area is called an infarct.
CVA in small, minor arteries >> infarcts = small;
CVA in major vessel >> infarcts = large
-Thrombosis  - a blood clot that remains at the point at which it was formed
Most common cause: Atherosclerosis  () (fatty deposits build up inside the walls of
blood vessels, constricting the vessel more and more and possibly even completely
blocking it.
Because atherosclerosis often forms where two relatively large arteries branch off
from one single artery (bifurcation), the construction of blood flow tends to
influence relatively large areas of the brain.
-Embolism  - a clot (can be another substance, e.g. bubble of air / piece of fat) that travels in
the bloodstream from one part of the body to another.
Substance travels from a spot where the arteries are relatively large to a place where the
arteries are smaller than the point of original formation, so a clot that previously did not
completely block the flow of blood might suddenly do so at another location.
-Hemorrhage  - interruption in blood supply to the brain can be caused by the breakage of a
blood vessel.
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