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Lecture 20

PSYC 211 Lecture Notes - Lecture 20: Chemical Substance, Apolipoprotein, Atherosclerosis

21 pages72 viewsFall 2017

Department
Psychology
Course Code
PSYC 211
Professor
Jonathan Britt
Lecture
20

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PSYC 211
Chapter 14
Major categories of the neuropathological conditions that the brain can sustain:
1. Tumors
2. Seizure Disorders
3. Cerebrovascular accidents
4. Disorders of Development
5. Degenerative Disorders
6. Disorders caused by infectious disease
Tumors
A tumor is a mass of cells whose growth is uncontrolled and that serves no useful function
Some are malignant - cancerous
o Lacks a distinct border and may metastasize
Others are benign - harmless/non-cancerous
o Has a distinct border and cannot metastasize
The major distinction between malignancy and benignancy is whether the tumor is encapsulated -
whether there is a distinct border between the mass of tumor cells and the surrounding tissue
o If the border exists, tumor is benign; surgeon can cut it out and it will not regrow
o If the tumor grows by infiltrating the surrounding tissue, there will be no clear-cut border
between the tumor and the normal tissue
If the surgeon removes the tumor, some cells may be missed and those cells will
produce a new tumor
Malignant tumors often give rise to metastases - the process by which cells break off of a tumor,
travel through the vascular system (bloodstream), lodge in capillaries, and grow new tumors in
other locations in the body
Tumors damage brain tissue by 2 means:
o Compression and infiltration
o Any tumor in the brain (malignant or benign) can produce neurological symptoms and
threaten patient's life
Even a benign tumors occupies space and thus pushes against the brain
Compression can directly destroy brain tissue, or do so indirectly by blocking the flow
of cerebrospinal fluid and causing hydrocephalus
o Malignant tumors cause both compression and infiltration
As it grows, it invades the surrounding region and destroys cells in the way
Tumors arise from other cells found in the brain or from metastases originating elsewhere in the
body - not from neurons (mature neurons are not capable of division)
The most serious types of tumors are metastases and gliomas - derived from various glial cells
o Gliomas are usually very malignant and fast growing
o Malignancy of brain tumors are caused by rare subpopulation of cells
o Malignant gliomas contain tumor-initiating cells - cells that originate from transformations
of neural stem cells, rapidly proliferate, and give rise to a glioma
o Gliomas are more resistant to chemotherapy and radiation than most tumor cells, so the
survival rate from these tumors is low
Meningioma - an encapsulated, benign tumor consisting of cells that constitute the dura mater or
arachnoid membrane
o Composed of cells that constitute the meninges
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PSYC 211
o Originate in the part of the dura mater that is found between the two cerebral hemispheres,
or along the tentorium - sheet of dura mater lying between the occipital lobe and
cerebellum
o Case - woman (Mrs. R) whose sudden onset of seizures suggested the presence of a tumor
near the top of the primary motor cortex (meningioma)
Early symptoms were seizures localized in her foot (foot would shake)
Then seizure spread through her lower leg, and then her upper leg, whole body -
convulsions became more and more violent
Lost consciousness
Types of Brain Tumors:
Gliomas Glioblastoma multiforme (poorly differentiated glial cells) Astrocytoma (astrocytes)
Ependymoma (ependymal cells that line ventricles) Medulloblastoma (cells in roof of fourth ventricle) Oligodendrocytoma (oligodendrocytes)
Meningioma (cells of the meninges)
Pituitary adenoma (hormone-secreting cells of the pituitary gland)
Neurinoma (Schwann cells or cells of connective tissue covering cranial nerves)
Metastatic carcinoma (depends on the nature of the primary tumor)
Angioma (cells of blood vessels)
Pinealoma (cells of pineal gland)
Seizure Disorders
Seizure disorder - preferred term for epilepsy
o Has many causes
o 2nd most important category of neurological disorders - following stroke
Seizure is a period of sudden, excessive activity (excitability) of cerebral neurons
If neurons that make up the motor system are involved, seizures can cause a convulsion - wild,
uncontrollable activity of the muscles
o But most seizures don't cause convulsions
Seizures have physical causes
2 distinctions of seizures:
o Partial vs generalized and simple vs. complex
Partial seizures - begins at a focus and remains localized; doesn't generalize to the rest of the
brain
o Typically caused by a scarred region (caused by an old injury) or a developmental
abnormality (i.e. malformed blood vessel)
o Neurons involved in the seizure are restricted to a small part of the brain
o Symptoms can include sensory changes, motor activity (or both)
o Divided into 2 categories:
Simple seizures - do not cause loss in consciousness, but may cause changes in
consciousness; starts from focus point and remains localized
Ex: if it begins in or near the motor cortex then it can involve jerking movements
Mrs. R first seizure spell was a simply seizure
The excitation in the brain spread along the precentral gyrus
Seizure was triggered by an meningioma - tumor was pressing against the
"foot" region of the left primary motor cortex
Her second seizure spell was a complex seizure - she lost consciousness
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PSYC 211
Seizure localized in the occipital lobe may produce visual symptoms (temporary
blindness, spots of colour, flashes of light)
One in the parietal lobe can evoke somatosensations (temp. changes, feelings of
pins and needles)
Complex seizures - leads to loss in consciousness; starts from focus point and remains
localized
Generalized seizures - widespread, involving most of the brain
o Typically grow from a focus, but sometimes their origin is not discovered
Tonic-clonic seizure (grand mal seizure) - a generalized convulsive seizure (includes neurons in the
motor systems)
o Most severe form of seizure
o Often before having this kind of seizure, a person experiences warning symptoms
(i.e. changes in mood or sudden jerks of muscular activity) - the aura
Aura - sensation that precedes a seizure; it's nature depends on the location of the
seizure focus
Ex: structures in the temporal lobe are involved in control of emotions, so
seizures originating in that lobe will often begin with a change in emotional
state or mood
Could also cause hallucinations that include old memories
Presumable caused by excitation of neurons surrounding the seizure focus
o Beginning of tonic-clonic seizure is the tonic phase (1st phase)
All the patient's skeletal muscles contract fully
On some cases in can result in fracturing of the bones and the inability to breathe
o Second phase is the clonic phase
Patient shows rhythmic jerking movements (convulsions)
Intense activity in the autonomic system (sweating and salivation)
Loss of consciousness
After this phase the patient is usually exhausted and needs to sleep for long periods of
time
Children are especially susceptible to seizure disorders
o Most don't have tonic-clonic seizures, but have very brief seizures - spells of absence
o Absence seizure (petite mal) - characterized by periods of inattention; staring off into the
distance (and are not remembered)
Repeated eye blinks
Generalized seizure disorder
During this time they are unresponsive and do not notice their attacks
Can occur up to several hundred times a day
Can disrupt a child's school performance as a result
No long term consequences
Seizures can cause brain damage
o Approx. 50% of patient's with seizure disorders show evidence of damage to the
hippocampus
Hippocampal damage can be caused by a single episode of status epilepticus - a
condition in which the patient undergoes a series of seizures without regaining
consciousness
Damage is caused by an excessive release of glutamate during the seizure
o Amount of damage is correlated with the number and severity of seizures
Seizures have many causes:
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