PSYC 2800 Lecture Notes - Sleep Deprivation, Circadian Rhythm, Non-Rapid Eye Movement Sleep

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20 Apr 2012
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Lecture 2b *final+
What Does Sleep Accomplish?
Sleep As a Biological Adaptation
Sleep is an energy-conserving strategy
Gather food at optimal times and sleep to conserve energy the rest of
the time. Conserve energy so can hunt for food at appropriate time
Animals with nutrient-rich diets spend less time foraging for food and
more time sleeping
Animals that are predators sleep more than animals that are prey (can’t
afford because may get attacked)
Nocturnal or diurnal animals will sleep during those times in which they
cannot travel easily
Example: Humans can’t see well at night so active during daytime
Strangely possums sleep 19 hours a day but not carnivores
Sleep As a Biological Adaptation
Basic Rest-Activity Cycle (BRAC)
Recurring cycle of temporal packets, about 90 minute periods in
humans, during which an animal’s level of arousal waxes and wanes
Activity and rest
Examples: School classes, work periods, meal times, NREM-REM
cycles, all around 90 minutes
Cycles so fundamental that it cannot be turned off even at night, so
the body is paralyzed during REM sleep to prevent interruptions
throughout sleep
Actual circadian rhythms controlled by cortisol, which doesn’t have
90 minute cycle. Low= inactive.
Sleep As a Restorative Process
Sleep not adaptive but restorative
Possible Hypotheses
Chemical events that provide energy to cells may be reduced during
waking and are replenished during sleep BUT
Fatigue and alertness may simply be aspects of the circadian rhythms
and have nothing to do with wear and tear on the body
- Evidence conflicting
Sleep Deprivation
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Recuperative/restorative theories make specific predictions about sleep
deprivation:
Long periods of wakefulness will produce physiological and
behavioural disturbances
Disturbances will grow steadily worse as deprivation continues
After a period of deprivation has ended, much of missed sleep will be
regained (rebound). Ex: Miss 2 nights sleep, third night sleep longer
to make up for it
Case of Randy Gardner
1965 Science Fair project
Stayed awake for 264 hours (about 11 days)
Long periods of wakefulness will produce physiological and
behavioral disturbances
True. Cognitive capabilities in decline, ability to access info,
short term memory, response times all affected
Disturbances will grow steadily worse as deprivation continues
True.
After a period of deprivation has ended, much of missed sleep will be
regained
No. After 11 days, slept 8-10 hours and thats all
Restorative theory not all together accurate
What are you own experiences?
Most people who sleep irregularly or little, do so because they are under stress
N.B.: Shift workers/Jet lag forced to do so (sleep deprivation), circadian
rhythms altered. Can have significant impacts on health.
We also either under- or over-estimate the effects of sleep deprivation in
ourselves.
Tend do overestimate how much sleep deprivation we have (enter stage 1
without realizing when toss and turn).
Short term sleep deprivation can alleviate depression. Disrupted cortisol in
depression.
Sleep Deprivation: Studies
Usually self report, memory tasks, motor tasks
Measures: Sleepiness, mood, cognition, motor performance, physiological
function (eyemovement, hormones, etc.)
Complete deprivation
3 or 4 days max (more unethical)
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