Sleep Needs, Sleep Stages and Sleep DeprivationAltered States of Awareness

Why do we need Sleep?There isnt one definitive explanation of why we need sleep, in fact there are researchers who dont believe that we need sleep.

Most of the research that has been done into sleep deprivation shows that there is a negative effect on our health and so it is therefore assumed that sleep is a necessary activity for our ongoing wellbeing.

The amount of sleep needed varies from individual to individual and can depend on factors such as age. It is widely accepted that we need, on average approx. 6 10 hours per night.

Researchers argue that there is a range of reasons why we need to sleep, including..energy conservationrepair and restorationto consolidate memories

Energy conservationWhen we sleep, we use less energy than when we are awake. One of the key reasons for this is that our metabolic rate is lower. We use more energy while walking around, or even while just sitting, than when we sleep. Sleep allows the body to conserve energy, which is shown by the fact that our temperature drops we sleep. Our bodys dont work as hard when we have a slightly lower temperature. At the same time though, our brains still use quite a lot of energy, particularly during the REM stage of sleep.

Repair and RestorationThe Human Growth Hormone circadian rhythm shows an increase in HGH production during sleep which indicates that a lot of cell repair occurs during sleep. Being at rest while we are awake also allows much cell repair to occur. During sleep, our body strengthens its immune system and eliminates waste products from muscles.

Memory consolidationThere is much research to support the idea that sleeping allows our brain to consolidate learning and, in particular, to make sense of our memories and store them in a logical and accessible. People who get plenty of deep NREM sleep in the first half of the night and REM sleep in the second half improve their ability to perform spatial tasks.

The Stages of Sleep

Stage 1 Non-REM SleepAfter 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 movementGenerally, 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 NREMStage 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 them.

Stage 4 NREMThe 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 restThis 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 StageWhen you enter the REM stage, your brain suddenly becomes much more activeREM Sleep stage. Brain wave scan or EEG (Top 2 channels) shows low-amplitude, mixed frequency waves called theta waves, with some alpha waves.

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. 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. A man experiences penile erections; a woman experiences clitoral engorgement. The sleepers' large muscles are literally paralysed. 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. .

Awake, responsive immediately, can recall all eventsStage 1 sleep, mind drifting, easy to awake, memory consolidation ceasesStage 2 sleep, mind drifting, more difficult to awakeStage 3,4 sleep, mind fairly blank, very difficult to awakeRapid Eye Movement (REM) sleep, vivid dreams, emotional arousal, can awake feeling alertBrain WavesEye MovementsMuscle TensionAwake and Sleep Stages< 50% alphaK-complexes, sleep spindles20-50% Delta>50% DeltaAlpha (8-12Hz)Beta, theta wavesSlow Eye MovementsReduced EMGLarge Muscle ParalysisBeta, Saw-tooth WavesRapid Conjugate Eye Movements

A Normal Nights Sleep?A normal nights sleep is not as we often imagine a smooth continuous event. We often get disturbed by interruptions to sleep and talk about having a bad nights sleep if it we have woken on one or two occasions in the evening.

This how ever is perfectly normal!

A normal nights sleep.

Sleep DeprivationOur bodies maintain SLEEP STASIS which means that our bodies try to maintain the average of 8 hours of sleep per night. When we do not have enough sleep we experience sleep debt. Sleep debt causesSleep pressure the feeling of sleepinessFatigueMemory difficultiesStudies have shown that sleep deprivation has similar effects on reaction times to being drunk.

Sleep DeprivationSleep deprivation is also linked with other health issues. In fact sleep deprivation causes very similar health complications to long periods of stress.Heart DiseaseIncreased blood pressureDigestive problemsIrritabilityIncreased likelihood of mental illness.