MikeCracknell
19th July 2006, 21:15
For anyone who gives a dam - found this, and thought it may be of interest to those who spend all night out on the lash!
The science of sleep
Sleep science
We spend a third of our lives doing it.
Napoleon, Florence Nightingale and Margaret Thatcher got by on four hours a
night.
Thomas Edison claimed it was waste of time.
Why do we sleep?
So why do we sleep? This is a question that has baffled scientists for
centuries and the answer is, no one is really sure. Some believe that sleep
gives the body a chance to recuperate from the day's activities but in
reality, the amount of energy saved by sleeping for even eight hours is
miniscule - about 50 kCal, the same amount of energy in a piece of toast.
We have to sleep because it is essential to maintaining normal levels of
cognitive skills such as speech, memory, innovative and flexible thinking.
In other words, sleep plays a significant role in brain development.
What would happen if we didn't sleep?
Irritable man
A good way to understand the role of sleep is to look at what would happen
if we didn't sleep. Lack of sleep has serious effects on our brain's ability
to function. If you've ever pulled an all-nighter, you'll be familiar with
the following after-effects: grumpiness, grogginess, irritability and
forgetfulness. After just one night without sleep, concentration becomes
more difficult and attention span shortens considerably.
With continued lack of sufficient sleep, the part of the brain that controls
language, memory, planning and sense of time is severely affected,
practically shutting down. In fact, 17 hours of sustained wakefulness leads
to a decrease in performance equivalent to a blood alcohol level of 0.05%
(two glasses of wine). This is the legal drink driving limit in the UK.
Research also shows that sleep-deprived individuals often have difficulty in
responding to rapidly changing situations and making rational judgements. In
real life situations, the consequences are grave and lack of sleep is said
to have been be a contributory factor to a number of international disasters
such as Exxon Valdez, Chernobyl, Three Mile Island and the Challenger
shuttle explosion.
Sleep deprivation not only has a major impact on cognitive functioning but
also on emotional and physical health. Disorders such as sleep apnoea which
result in excessive daytime sleepiness have been linked to stress and high
blood pressure. Research has also suggested that sleep loss may increase the
risk of obesity because chemicals and hormones that play a key role in
controlling appetite and weight gain are released during sleep.
What happens when we sleep?
REM
What happens every time we get a bit of shut eye? Sleep occurs in a
recurring cycle of 90 to 110 minutes and is divided into two categories:
non-REM (which is further split into four stages) and REM sleep.
Non-REM sleep
Stage one: Light Sleep
During the first stage of sleep, we're half awake and half asleep. Our
muscle activity slows down and slight twitching may occur. This is a period
of light sleep, meaning we can be awakened easily at this stage.
Stage two: True Sleep
Within ten minutes of light sleep, we enter stage two, which lasts around 20
minutes. The breathing pattern and heart rate start to slow down. This
period accounts for the largest part of human sleep.
Stages three and four: Deep Sleep
During stage three, the brain begins to produce delta waves, a type of wave
that is large (high amplitude) and slow (low frequency). Breathing and heart
rate are at their lowest levels.
Stage four is characterised by rhythmic breathing and limited muscle
activity. If we are awakened during deep sleep we do not adjust immediately
and often feel groggy and disoriented for several minutes after waking up.
Some children experience bed-wetting, night terrors, or sleepwalking during
this stage.
Closed eye
REM sleep
The first rapid eye movement (REM) period usually begins about 70 to 90
minutes after we fall asleep. We have around three to five REM episodes a
night.
Although we are not conscious, the brain is very active - often more so than
when we are awake. This is the period when most dreams occur. Our eyes dart
around (hence the name), our breathing rate and blood pressure rise.
However, our bodies are effectively paralysed, said to be nature's way of
preventing us from acting out our dreams.
After REM sleep, the whole cycle begins again.
How much sleep is required?
There is no set amount of time that everyone needs to sleep, since it varies
from person to person. Results from the sleep profiler indicate that people
like to sleep anywhere between 5 and 11 hours, with the average being 7.75
hours.
Jim Horne from Loughborough University's Sleep Research Centre has a simple
answer though: "The amount of sleep we require is what we need not to be
sleepy in the daytime."
Even animals require varied amounts of sleep:
Species Average total sleep time per day
Python 18 hrs
Tiger 15.8 hrs
Cat 12.1 hrs
Chimpanzee 9.7 hrs
Sheep 3.8 hrs
African elephant 3.3 hrs
Giraffe 1.9 hr
The current world record for the longest period without sleep is 11 days,
set by Randy Gardner in 1965. Four days into the research, he began
hallucinating. This was followed by a delusion where he thought he was a
famous footballer. Surprisingly, Randy was actually functioning quite well
at the end of his research and he could still beat the scientist at pinball.
The science of sleep
Sleep science
We spend a third of our lives doing it.
Napoleon, Florence Nightingale and Margaret Thatcher got by on four hours a
night.
Thomas Edison claimed it was waste of time.
Why do we sleep?
So why do we sleep? This is a question that has baffled scientists for
centuries and the answer is, no one is really sure. Some believe that sleep
gives the body a chance to recuperate from the day's activities but in
reality, the amount of energy saved by sleeping for even eight hours is
miniscule - about 50 kCal, the same amount of energy in a piece of toast.
We have to sleep because it is essential to maintaining normal levels of
cognitive skills such as speech, memory, innovative and flexible thinking.
In other words, sleep plays a significant role in brain development.
What would happen if we didn't sleep?
Irritable man
A good way to understand the role of sleep is to look at what would happen
if we didn't sleep. Lack of sleep has serious effects on our brain's ability
to function. If you've ever pulled an all-nighter, you'll be familiar with
the following after-effects: grumpiness, grogginess, irritability and
forgetfulness. After just one night without sleep, concentration becomes
more difficult and attention span shortens considerably.
With continued lack of sufficient sleep, the part of the brain that controls
language, memory, planning and sense of time is severely affected,
practically shutting down. In fact, 17 hours of sustained wakefulness leads
to a decrease in performance equivalent to a blood alcohol level of 0.05%
(two glasses of wine). This is the legal drink driving limit in the UK.
Research also shows that sleep-deprived individuals often have difficulty in
responding to rapidly changing situations and making rational judgements. In
real life situations, the consequences are grave and lack of sleep is said
to have been be a contributory factor to a number of international disasters
such as Exxon Valdez, Chernobyl, Three Mile Island and the Challenger
shuttle explosion.
Sleep deprivation not only has a major impact on cognitive functioning but
also on emotional and physical health. Disorders such as sleep apnoea which
result in excessive daytime sleepiness have been linked to stress and high
blood pressure. Research has also suggested that sleep loss may increase the
risk of obesity because chemicals and hormones that play a key role in
controlling appetite and weight gain are released during sleep.
What happens when we sleep?
REM
What happens every time we get a bit of shut eye? Sleep occurs in a
recurring cycle of 90 to 110 minutes and is divided into two categories:
non-REM (which is further split into four stages) and REM sleep.
Non-REM sleep
Stage one: Light Sleep
During the first stage of sleep, we're half awake and half asleep. Our
muscle activity slows down and slight twitching may occur. This is a period
of light sleep, meaning we can be awakened easily at this stage.
Stage two: True Sleep
Within ten minutes of light sleep, we enter stage two, which lasts around 20
minutes. The breathing pattern and heart rate start to slow down. This
period accounts for the largest part of human sleep.
Stages three and four: Deep Sleep
During stage three, the brain begins to produce delta waves, a type of wave
that is large (high amplitude) and slow (low frequency). Breathing and heart
rate are at their lowest levels.
Stage four is characterised by rhythmic breathing and limited muscle
activity. If we are awakened during deep sleep we do not adjust immediately
and often feel groggy and disoriented for several minutes after waking up.
Some children experience bed-wetting, night terrors, or sleepwalking during
this stage.
Closed eye
REM sleep
The first rapid eye movement (REM) period usually begins about 70 to 90
minutes after we fall asleep. We have around three to five REM episodes a
night.
Although we are not conscious, the brain is very active - often more so than
when we are awake. This is the period when most dreams occur. Our eyes dart
around (hence the name), our breathing rate and blood pressure rise.
However, our bodies are effectively paralysed, said to be nature's way of
preventing us from acting out our dreams.
After REM sleep, the whole cycle begins again.
How much sleep is required?
There is no set amount of time that everyone needs to sleep, since it varies
from person to person. Results from the sleep profiler indicate that people
like to sleep anywhere between 5 and 11 hours, with the average being 7.75
hours.
Jim Horne from Loughborough University's Sleep Research Centre has a simple
answer though: "The amount of sleep we require is what we need not to be
sleepy in the daytime."
Even animals require varied amounts of sleep:
Species Average total sleep time per day
Python 18 hrs
Tiger 15.8 hrs
Cat 12.1 hrs
Chimpanzee 9.7 hrs
Sheep 3.8 hrs
African elephant 3.3 hrs
Giraffe 1.9 hr
The current world record for the longest period without sleep is 11 days,
set by Randy Gardner in 1965. Four days into the research, he began
hallucinating. This was followed by a delusion where he thought he was a
famous footballer. Surprisingly, Randy was actually functioning quite well
at the end of his research and he could still beat the scientist at pinball.