PSYCH101 Lecture Notes - Circadian Clock, Slow-Wave Sleep, Circadian Rhythm

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16 Oct 2011

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Chapter 8- Sleep and Dreams
- When you are asleep, the brain`s auditory cortex will still respond to sound stimuli
Biological Rhythms and Sleep
- Circadian Rhythm
o Our bodies synchronize roughly to the 24 hour cycle of day and night and through a
biological clock called the circadian rhythm
o Body temperature rises as the morning approaches, it peaks during the day and dips for
a time in early afternoon and then begins to drop again when we sleep, thinking and
memory are sharpest when we are at our daily peak for circadian arousal... when we
pull an all nighter we feel the groggiest at 4 am and get our second wind after our
normal wake up time comes
o Bright lights during the morning tweaks he circadian clock by activating light sensitive
retinal proteins...these proteins control the circadian clock by triggering signals to the
brains suprachiasmatic nucleus (SCN)a pair of rice grain sized 20,000 cell cluster in
the hypothalamus ...
o Suprachiasmatic nucleus- does its job in part by causing the brain`s pineal gland to
decrease its production of the sleep inducing hormone melatonin in the morning and
increase it during the evening
o bright light at night helps delay sleep... resetting our biological clock when we stay up
late and sleep in on weekends
o our ancestors body clocks were attuned to the rising and setting sun of the 24 hour
day... many young adults today adopt something closer to a 25 hour day by staying up
too late to get 8 hours of sleep
this is due to the invention of the lightbulb... being bathed in light, disrupts our
24 hour biological clock... (remember before... artificial light delays sleep)
Sleep Stages
- consciousness fades when we are sleeping as it overtakes different parts of our brains cortex to
stop communicating
- our brain in a sleeping state does not emit a constant dial tone because sleep has its own
biological rhythm..about every 90 minutes we pass through a cycle of five distinct sleep stages
- REM sleep (rapid eye movement sleep) was discovered by a graduate student who put an
electroencephalograph near his sons eyes to record the rolling eye movements .... he realized
that the fast jerky eye movements were accompanied by energetic brain activity
- To study if similar cycles occur during adult sleep ... researchers tape electrodes to the scalp to
detect brainwaves, just outside your eyes to detect eye movements and on your chin to detect
muscle tension.... other devices allow the researcher to record your heart rate and respiration
rate and your genital arousal
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Chapter 8- Sleep and Dreams
When you are in bed with your eyes closed, the researcher in the next room sees on the EEG
(electroenecephalograph) the relatively slow alpha waves of your awake but relaxed ... you
eventually slip into sleep
- In a study, a man asked another man to press a button everytime he saw a flash, he missed one
after a while because he claimed there was none, but there was and it was because he had
fallen asleep for 2 seconds
- During the stage 1 sleep you may experience fantastic images, like hallucinationssensory
experiences that occur without a sensory stimulus... you may have a sensation of falling at which
your body may suddenly jerk or floating weightlessly
o Such hypnagogic sensations may later be incorporated into memories
- After relaxing some more after stage 1, you proceed to stage 2 sleep which lasts about 20
minutes ... it is characterized by periodic appearance of sleep spindles (bursts of rapid, rhythmic
brain-wave activity) you are now clearly asleep. Sleeptalking usually occurs during this stage and
you can easily be woken up
- Then for the next few minutes you go through the transitional stage 3 to the deep sleep in stage
4, in stage 3 and increasingly in stage 4 your brain emits large slow delta waves, these two slow
wave stages last for about 30 minutes during which would be hard to wake up. It is during this
stage that children begin to wet the bed or begin sleep walking.... about 20 percent of 3-12 year
olds have atleast one episode of sleep walking, usually lasting 2-10 minutes.... some 5% have
repeated episodes
- REM Sleep
o After about ½ hour after you fall asleep, rather than continuing into slumber, you go
back to stage 3 and 2 and you enter the most intriguing sleep phaseREM sleep... for
about 10 minutes your brain waves become rapid and saw toothed more like those of
nearly awake in stage 1 but unlike stage 1 sleep during REM sleep your heart rate rises
your breathing becomes rapid and irregular and every half minute or so your eyes dart
around in a momentary burst of activity behind closed lids
o Your genitals become aroused during REM sleep (except when you have very scary
dreams), you have an erection or increased vaginal lubrication regardless of the dream
being sexual or not... therefore morning erection stems from last nights REM period
Many men who have erectile dysfunction have problems achieving erections
during REM sleep and so suggests the problem is not their genitals
o Brains motor cortex is active during REM sleep, your brainstem blocks messages leaving
muscles relaxed such that besides the occasional twitches you’re essentially paralyzed
and you can not be easily awakened during REM sleep
REM sleep = paradoxical sleep because the body is internally aroused and
externally calm
o Rapid eye movement during REM sleep announces the beginning of a new dream
o REM sleep drams are often emotional, usually storylike and more richly hallucinatory
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