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Explanations of Narcolepsy Essay 24 Marks - BIORHYTMS
Explanation of Narcolepsy Essay worth 24 marks and scored full marks = A*.
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Explanations of Narcolepsy (8+16)Narcolepsy is a disorder where individuals feel sudden and unexpected urges to sleep, this can occur
at irregular and unexpected times. There is a neural explanation for narcolepsy. Van Economo found
that his patients who had muscle weakness and extreme sleepiness had damage to their
hypothalamus. The hypothalamus contains cells which secrete hypocretin, which is a
neurotransmitter which regulates arousal and wakefulness. It has been found that people with
narcolepsy can have up to an 80% reduction in hypocretin. This is supported by a study of a man
who developed narcolepsy after he has a stroke, he had a reduction in hypocretin in his
cerebrospinal fluid. Supports, as demonstrates that narcolepsy and hyporcretin are linked. However
a problem with this research is that is a case study of one individual. We cannot be sure that the
stroke did not cause other damage which also has caused the onset of narcolepsy. This issue
question show effectively the study can be used to support the neural explanation of narcolepsy.
Also supported by Aril, who studied a girl who has no history of sleep disorders, but she had a brain
tumour. She underwent surgery to remove her tumour in her hypothalamus. After the surgery she
had urges to sleep and fell asleep during everyday tasks. She was found to have a reduction in
hypocretin in her cerebral fluid. MRI scans later confirmed that the surgery had damaged areas of
the hypothalamus. This supports as shows that by damaging the hypothalamus it causes a reduction
on hyprocretin which leads to tiredness, and thus narcolepsy. Gerashchenko’s study also supports,
he destroyed the cells in lateral hypothalamus of rats. He found a relationship between number of
cells damaged and hypocretin levels in the cerebrospinal fluid. This supports, as it demonstrates that
hypocretin and narcolepsy are linked. However, a problem with this research is that it was
conducted on animals, so we cannot generalise the findings to humans as we cannot be sure that
hypocretin has the same functions in humans. This issue questions how effectively the study can be
used to support the neural explanation of narcolepsy. The neural explanation is also supported by
research which administered hypocretin to dogs. It found that is caused a reduction in cataplexy,
which is loss of muscle tone. People who have narcolepsy sometimes suffer from cataplexy. This
supports, as it demonstrates a link between hypocretin and narcolepsy. Another study supporting
that hypocretin and narcolepsy are linked comes from dement. He found that mice who didn’t have
hypocretin in brains developed symptoms of narcolepsy. Parkinson’s disease which is a degenerative
brain disease, has said to make patients feel tired and display sleep problems resembling narcolepsy.
Post mortems found that patients had up to a 62% reduction of hypocretin in their brains, this
therefore helps to explain why they experienced tiredness. This supports, as again shows that
hypocretin and narcolepsy are linked, and that a reduction in hypocretin is likely to cause symptoms
of narcolepsy. Provgil, which is a stimulant is used to treat narcolepsy, it helps to stimulate the
production of hypcretin. It has been shown to be successful, so it therefore supports idea that
hypocretin and narcolepsy are linked, and thus narcolepsy has a neural explanation. This is because
if the treatment works, the theory on which it is based must have some credibility.
Another explanation is through genetics. It is thought that dogs may inherit a form of narcolepsy.
This has led to people breeding narcoleptic dogs in order to identify if there is a gene responsible. It
is found that the gene on the 12th chromosome is responsible for regulating brain receptors for
hypothalamus. However, this is not supported by a twin study which only found a 30% concordance
rate between narcolepsy and mz twins. This strongly suggests that there is an environmental
influence, as if narcolepsy was solely due to genes we would expect 100% concordance rate as mz
twins have 100% of the same genes. A study which supports genetic explanation showed that a
mutation of a gene in dogs affected hypocretin production. However, research as not yet found the
gene in humans so limits how much the research can be used to support genetic explanation.
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