xiii. DSPS-sleep

27 November 2005 at 16:52 | Posted in Circadian rhythm | Leave a comment
Tags: , ,
 
Yes, I drew that myself.  Some people learn from seeing a drawing — I learn from making one.  Win-win, I hope 🙂 
 
 We accrue sleep debt all day long.  Assuming we go to sleep 6-7 hours before the temperature curve bottoms out (and haven’t napped), the homeostatic drive for sleep keeps us under the first four hours or so.  Then the circadian drive for sleep keeps us asleep until the time our body clock determines we should awaken.  The time of the lowest core body temperature (red curve) is called “nadir”. 
 
The blue curve shows the level of melatonin in the blood through the night.  It is rapidly suppressed when (bright) light strikes the retina. 
 
The timeline at the top represents a normal adult.  The line at the bottom represents Delayed Sleep-Phase Syndrome where the delay shown is about four hours.  It could have been anything more than two. 
 
Key to an understanding of this, is realizing that our preferred wake time is hard-coded.  Even if she goes late to bed, the normal adult won’t sleep too much later than eight.  And she’s not going to get the hours she needs if she doesn’t go to bed somewhere near six hours before nadir.

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Next post:  xiv. THAT’s what friends are!

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