The Biological Clock
We are all familiar with the "biological clock." Some of us are morning
people; some are night people. Regardless of our preferences, we are all governed by a biological
clock with an approximate cycle of 24 hours corresponding to the Earth's
rotation time. Biologically speaking, this molecular clock is known as the
circadian rhythm. Researchers at Northwestern University have recently
discovered remarkable similarities in the main components of clocks across
organisms--from invertebrates to mammals.
This is the first study to show these similarities in circadian rhythm
mechanisms. Researchers found that the same gene, dubbed the clock gene, has the
same function in both flies and mice. Three clock genes in particular are the
same across the different organisms and seem to form the basis for the
rudimentary clock system that has been preserved.
The genes work by a feedback loop of both activation and inhibition forming the
rudimentary system. Like the oscillation of a pendulum, the process can "swing"
back and forth and, in turn, regulate whether the clock is "on" or "off." This
loop seems to be the basis of the system in animals.
Circadian rhythms regulate a variety of activities (such as the morning and
night people mentioned above). The rhythms contribute to such things as jet lag
and many sleep disorders.
Scientists hope that by studying the underlying mechanism, they will be able to
predict why certain anomalies occur at particular times of the day, for instance
why people seem to be more prone to heart attacks in the early morning versus
later in the day.
The Stages of Sleep
Stage 1 Non-REM Sleep
After the sleeper falls asleep, he or she enters into what is known as the Stage
1 of non- REM sleep.
Stage 1 sleep is the period we "drift off."
Stage 1 NREM Sleep is characterized by the following:
Breathing becomes slow and even
The heartbeat becomes regular
Blood pressure falls
Brain temperature decreases
Blood flow to the brain is reduced
Little or no body movement.
Generally, this description of bodily functions characterizes all non-REM sleep.
Stage 1 sleep might be called a kind of twilight time. It's initial appearance
lasts up to ten minutes in most sleepers.
Brain waves become smaller, slower, and somewhat irregular characterized by a
low-voltage fast EEG.
This portion of sleep is distinguished by drifting thoughts and dreams that move
from the real to the fantastic, along with a kind of floating feeling.
The sleeper is still easily awakened and might even deny having slept.
Stage 2 NREM
Stage 2 is an intermediate stage of sleep. It initially lasts about twenty
minutes. The sleeper will gradually descend deeper into sleep, becoming more and
more detached from the outside world and progressively more difficult to awaken.
Stage 2 is characterized by:
Larger brain waves and occasional quick bursts of
activity.
The sleeper will not see anything even if the eyes are opened.
A sleeper can easily be awakened by sounds.
Bodily functions slow down. Blood pressure, metabolism, secretions, and cardiac
activity decrease.
Stage 3 NREM
Stage 3 is the beginning of deep sleep, occurring about thirty to forty five
minutes after you first fall asleep.
Stage 3 is characterized by:
Brain waves are slow (at the rate of 0.5 to 4 per second)
and quite large (five times the size of waves in Stage 2). These brain waves are
known as delta waves.
The sleeper is far more difficult to awaken as compared to stage 1 or 2 sleep.
It takes a louder noise or an active attempt to wake him or her.
Stage 4 NREM
The deepest sleep occurs in Stage 4.
Stage 4 is characterized by:
The brain waves (called delta brain waves) are quite
large, making a slow, jagged pattern on the EEG.
The sleeper experiences virtual oblivion. If the sleeper is a sleepwalker or a
bed wetter, those activities will begin in this phase.
Bodily functions continue to decline to the deepest possible state of physical
rest.
This first period of deep sleep is the deepest. The sleeper awakened from deep
sleep will probably be groggy, confused, or disoriented. He or she may
experience "sleep inertia" or "sleep drunkenness," seeming unable to function
normally for quite some time.
After the first phase of deep sleep ends, the sleeper returns to Stage 2 and
then enters the REM state.
REM Sleep Stage
Characteristics of REM State
Brain waves are small and irregular, with big bursts of
eye activity. The brain wave activity at this time resembles waking more than it
does sleeping.
The four NREM phases are characterized by progressive relaxation. But during REM
phase, the body's activity perks up considerably.
Blood pressure may increase drastically.
Pulse rates increase in an irregular way
The sleeper with cardiac problems faces the greatest risk of heart attack at
this time.
Breathing becomes irregular and oxygen consumption increases.
The chin is slack during REM sleep
The face, toes and fingers may twitch.
The sleepers' large muscles are literally paralyzed. They cannot move their
torsos, arms, or legs.
The body seems to have abandoned its effort to regulate its temperature during
the REM phase.
Shivering and sweating cease at this time, and the body's temperature drifts
gradually toward the temperature of its environment.
The first REM period is usually brief. After this, the sleeper may wake up
briefly. This is quite normal. A good sleeper may not remember it the next day.
A poor sleeper, however, may wake up at this point and have difficulty getting
back to sleep.