Disorders of sleep affect when and also how we sleep
looking at two main disorders, these are ; Narcolepsy and Insomnia
Symptom's - cataplexy ( loss of muscle movement)
- sudden sleep at innapropriate times
There are three primary explanations as to the cause of narcolepsy
These are REM, The HLA eplanation, The hypocretin explanation
During REM sleep, muscle paralysis takes place.
narcolepsy is just this paraysis (caused by the medula) at the wrong time
activity in the medula (INCREASES) muscle tone (DECREASES) = cataplexy
Siegel et al - looked at the activity in the medula in dogs during cataplexy. Activity was high.
this shows that there is a link between the lack of muscle tone in cataplaxy + the medula as in REM sleep
Schenkel + siegal - then destroyed the medulla in cats + they moved during REM as if awake.
This shows that muscle paralysis doesn't happen without the medulla making it the cause of cataplexy.
However not all people with narcolepsy have cataplexy!
the HLA explanation
Your immune system is attacking cells nside your body which is causing narcolepsy
Honda et al - found an unusual version of the HLA complex and showed 100% of a sample of narcoleptics in Japan had this unusual complex!
This can't just be coincedence!
Other studies, however have not shown this high concordance rate so what about those people?
The Hypocretin Explanation
Not enough Hypocretin causes narcolepsy
Thannickal et al - when post mortems on narcoleptics, 90% had below average hypocretin producing nueron's.
this estalishes a strong link between hypocretin and narcolepsy however it may be a result of narcolepsy not the other way round.
all explanations appear weak at first glance although there is clearly a link between all thee, one explantion is not the answer.
Links between all ideas!!
Nishino et al - showed that (DECREASE) in Hypocretin = (INCREASE) in medulla = (DECREASE) in muscle tone
This establishes a link between the REM explanation + hypocretin
if the HLA explanation can be linked to attacking hypocretin producing neurones then this is genetic form of the HLA complex causes Low hypocretin which leads to low muscle tone!
three types on insomnia;
1.) fatal familial insomnia - We know the genetic cause
2.) Secondary insomnia - Everyone has stresses and colds
3.) Primary insomnia - We don't know the Cause
What can cause it;
Geriatics Insomnia - Garfinkel - gave geriatrics more melatonin + sleep inproves showing a possible cause for this insomnia is low melatonin production.
We inherit Genes from out parents that give us the gene for insomnia
Watson et al - studied MZ + DZ twins and found a 47% concordance in MZ and 15% in DZ
STRESS - (DIATHESIS)
Suggests we have a predisposition from genes to be an insomniac but this is shaped by enviromental factors. e.g. Bed times as a child
This has now been developed by Spielma + Glovinsky
there is; predisposed, precepitation, perpetuation
This is the best explanation