phooey

Thursday, February 28, 2008

my cicardian rhythmn is so messed up. i'm so totally suferring from insomnia zzz :(
i just cant sleep :/
and i didnt sleep in the afternoon today
anyhow, thought i'd do a bit of reading: the sleep cycle
really interesting
and think i better try sleep now cos sleep deprivation leads to an increased risk of obesity :/
and i gotta be in school in less than 5 hrs

How we fall asleep
Our bodies provoke us to sleep by sending messages from our circadian clocks – our inner time-keeping, temperature-fluctuating, enzyme-controlling devices. The circadian clock works in tandem with adenosine, a neurotransmitter that “turns down” many of the bodily processes that make us feel awake. Adenosine is created as our cells create the power needed to move us though the day. As the level of adenosine builds up in our brains, we feel sleepier. Along with corresponding messages from the circadian clock, this alerts us that its time to sleep.

Prior to starting the sleep cycle, we first spend a few moments in a state of “relaxed wakefulness”. Most people stay in this stage for less than ten minutes, but the time you spend in relaxed wakefulness can offer clues to how well you are sleeping. If you are falling asleep the moment your head hits the pillow, you are either a very good sleeper, or you are extremely sleep deprived.

Stages of sleep: the sleep cycle
Sleep is a periodic state of rest during which consciousness of the world is interrupted. Additionally, sleep is marked by:

decreased movement of the skeletal muscles;
a relaxed posture, usually lying down;
reduced response to stimulation, such as sounds and touch;
slowed-down metabolism; and
complex and active brain wave patterns.
Sleep is divided into two types: REM (Rapid Eye Movement) sleep and NREM (non-REM) sleep. REM sleep is when we dream. NREM sleep is further divided into four stages. A typical night of sleep follows this pattern:

Stage 1 (Drowsiness) - When you first fall asleep, you are in Stage 1 sleep (Drowsiness). Stage 1 lasts just five or ten minutes. Eyes move slowly under the eyelids, and muscle activity slows down. You are easily awakened during Stage 1 sleep.
Stage 2 (Light Sleep) -Next, you go into Stage 2 sleep (Light Sleep). In Stage 2, eye movements stop, heart rate slows, and body temperature decreases.
Stages 3 & 4 (Deep Sleep) - Then you enter Stages 3 and 4 (Deep Sleep). During stages 3 and 4, you are difficult to awaken. People who are awakened during Deep Sleep do not adjust immediately and often feel groggy and disoriented for several minutes after they wake up. Children may experience bedwetting, night terrors, or sleepwalking during Deep Sleep.
REM sleep (Dream Sleep) - At about 70 to 90 minutes into your sleep cycle, you enter REM sleep. You usually have three to five REM episodes per night. Your eyes jerk rapidly in various directions under your eyelids, thus the name Rapid Eye Movement (REM) Sleep.
The first sleep cycles each night contain relatively short REM periods and long periods of deep sleep. As the night progresses, REM sleep periods increase in length while deep sleep decreases. By morning, people spend nearly all their sleep time in stages 1, 2, and REM.

What happens during the REM sleep stage?
During REM sleep, you dream actively, but your limb muscles are immobile. Your breathing is rapid, irregular, and shallow. Your heart rate increases, your blood pressure rises, males may have penile erections, and females may have clitoral enlargement. Your brain is at least as active during REM sleep as it is when you are awake.

Because your major muscles do not move during REM sleep, you will not act out your dreams. (Sleepwalking occurs during NREM sleep.)

Infants spend about 50 per cent of their sleep time in REM sleep; after infancy, you spend fifteen to twenty per cent of your sleep time in REM sleep.

The importance of deep sleep and dream sleep
Each stage of sleep offers benefits to the sleeper. However, deep sleep is perhaps the most vital stage, as it is the first stage that the brain attempts to recover when we are sleep deprived. If we do not get adequate deep sleep, we experience the strongest effects of sleep deprivation.

Deep sleep allows the brain to go on a little vacation needed to restore the energy we expend during our waking hours. Blood flow decreases to the brain in this stage, and redirects itself towards the muscles, restoring physical energy. Research also shows that immune functions increase during deep sleep.

REM sleep, or dream sleep, is also very important. This stage is associated with processing emotions, retaining memories, and relieving stress. Our brains suspend logic, and we lose all self-awareness – which is why we can experience ridiculous, irrational events in our dreams and believe them to be true.

If our REM sleep is disrupted one night, our bodies don't follow the normal sleep cycle progression the next time we doze off. Instead, we often go through extended periods of REM until we "catch up" on this stage of sleep. But, if deep sleep has been lost as well, our brain attempts to catch up on this stage first – in fact, the brain will try and make up all of the deep sleep it has lost and only half of the REM sleep.

webo @ 3:58 AM