JC- How Sleep Works.ppt

8/13/2019 JC- How Sleep Works.ppt

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How Sleep Works

by Justin Chuah, Group 239


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Characteristics of Sleep

We all know how sleep looks -- when we see someone sleeping, werecognize the following characteristics: If possible, the person will lie downto go to sleep. The person's eyesare closed. The person doesn't hear anythingunless it is a loud noise. The person breathesin a slow, rhythmic pattern. The person's musclesare completely relaxed. If sitting up, the

person may fall out of his or her chair as sleep deepens. During sleep, the person occasionally rolls over or rearranges his

or her body. This happens approximately once or twice an hour.This may be the body's way of making sure that no part of thebody or skin has its circulation cut off for too long a period oftime.


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Other Characteristics

In other words, a sleeping person is unconscious to mostthings happening in the environment. The biggest difference

between someone who is asleep and someone who hasfainted or gone into a coma is the fact that a sleepingperson can be aroused if the stimulus is strong enough. If

you shake the person, yell loudly or flash a bright light, asleeping person will wake up.

For any animal living in the wild, it just doesn't seem very

smart to design in a mandatory eight-hour period of near-total unconsciousness every day. Yet that is exactly whatevolution has done. So there must be a pretty good reasonfor it!


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Who Sleeps?

Reptiles, birds and mammals all sleep. That is, they becomeunconscious to their surroundings for periods of time. Somefish and amphibians reduce their awareness but do not everbecome unconscious like the higher vertebrates do. Insectsdo not appear to sleep, although they may become inactivein daylight or darkness.

By studying brainwaves, it is known that reptiles do notdream. Birds dream a little. Mammals all dream during sleep.

Different animals sleep in different ways. Some animals,

like humans, prefer to sleep in one long session. Otheranimals (dogs, for example) like to sleep in many shortbursts. Some sleep at night, while others sleep during theday.


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Really?

Cowscan sleep while standing up, but they

only dream if they lie down. Whales anddolphinsare "conscious breathers," andthey need to keep breathing while theysleep, so only one half of the brain sleeps

at a time


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Sleep and the Brain

If you attach an electroencephalographto a person's head,you can record the person's brainwave activity. An awakeand relaxed person generates alpha waves, which areconsistent oscillations at about 10 cycles per second. Analert person generates beta waves, which are about twiceas fast.

During sleep, two slower patterns called theta wavesanddelta wavestake over. Theta waves have oscillations in therange of 3.5 to 7 cycles per second, and delta waves have

oscillations of less than 3.5 cycles per second. As a personfalls asleep and sleep deepens, the brainwave patterns slowdown. The slower the brainwave patterns, the deeper thesleep -- a person deep in delta wave sleep is hardest towake up


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REM Sleep At several points during the night, something unexpected happens -- rapid

eye movement(REM) sleep occurs. Most people experience three to fiveintervals of REM sleep per night, and brainwaves during this period speedup to awake levels. If you ever watch a person or a dog experiencing REMsleep, you will see their eyes flickering back and forth rapidly. In manydogs and some people, arms, legs and facial muscles will twitch during REMsleep. Periods of sleep other than REM sleep are know as NREM (non-REM)sleep.

REM sleep is when you dream. If you wake up a person during REM sleep,the person can vividly recall dreams. If you wake up a person during NREMsleep, generally the person will not be dreaming.

You must have both REM and NREM sleep to get a good night's sleep. Anormal person will spend about 25 percent of the night in REM sleep, andthe rest in NREM. A REM session -- a dream -- lasts five to 30 minutes.

Medicine can hamper your ability to get a good night's sleep. Manymedicines, including most sleeping medicines, change the quality of sleepand the REM component of it.


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When You Miss Some Zzzzs...

One way to understand why we sleep is to look at what happens whenwe don't get enough: As you know if you have ever pulled an all-nighter, missing one night of sleep is not

fatal. A person will generally be irritable during the next day and will either slow down(become tired easily) or will be totally wired because of adrenalin.

If a person misses two nights of sleep, it gets worse. Concentration is difficult, andattention span falls by the wayside. Mistakes increase.

After three days, a person will start to hallucinate and clear thinking is impossible.With continued wakefulness a person can lose grasp of reality. Rats forced to stayawake continuously will eventually die, proving that sleep is essential.

A person who gets just a few hours of sleep per night can experience many of thesame problems over time.

Two other things are known to happen during sleep. Growth hormone in children issecreted during sleep, and chemicals important to the immune system are secretedduring sleep. You can become more prone to disease if you don't get enough sleep, anda child's growth can be stunted by sleep deprivation.


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Why Sleep?

Sleep gives the body a chance to repair musclesand other tissues, replace aging or dead cells, etc.

Sleep gives the brain a chance to organize andarchive memories. Dreams are thought by some tobe part of this process.

Sleep lowers our energy consumption, so we needthree meals a day rather than four or five. Sincewe can't do anything in the dark anyway, we mightas well "turn off" and save the energy.


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Why Sleep?

According to ScienceNewsOnline: Napless catsawaken interest in adenosine, sleep may be a way

of recharging the brain, using adenosine as asignal that the brain needs to rest: "Sinceadenosine secretion reflects brain cell activity,rising concentrations of this chemical may be howthe organ gauges that it has been burning up its

energy reserves and needs to shut down for awhile." Adenosine levels in the brain rise duringwakefulness and decline during sleep.


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Stages of Sleep


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Sleep Stages: Measures

There are 3 fundamental measures, on the basis of

defining sleep.

gross brain wave activityis considered, as

measured by an electroencephalogram (EEG)

muscle toneis measured with a electromyogram

(EMG) machine

eye movementis recorded via an electro-oculogram

(EOG)


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Sleep Stages: Waking through Stage 2

Figure 1.EEG, EOG, and EMG associated with different sleep stages


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Sleep Stages: Waking through Stage 2

When awake, most people exhibit brain wave, (EEG) patterns that can beclassified into two types of waves, beta and alpha.

Beta wavesare those associated with day to day wakefulness. These

waves are the highest in frequency and lowest in amplitude, and alsomore desynchronousthan other waves.This desynchrony makessense given that day to day mental activity consists of many cognitive,sensory, and motor activities and experiences, and, thus, when awake,we are mentally desynchronous as well.

During periods of relaxation, while still awake, our brain wavesbecome slower, increase in amplitude and become more

synchronous. These types of waves are called alpha waves. Forexample, such brain waves are often associated with states ofrelaxation and peacefulness during meditation and biofeedback. As wewill see in future lessons, recent evidence indicates that activities thatpromote alpha wave activity, appear to have positive health benefits


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Sleep Waves

The first stage of sleep is characterized by theta waves, whichare even slower in frequency and greater in amplitude thanalpha waves. The difference between relaxation and stage 1sleep is gradual and subtle. As the sleeper moves to stage 2sleep theta wave activity continues, interspersed with twounusual wave phenomena. These phenomena, which occurperiodically every minute or so, and are defining characteristicsof stage 2 sleep, are termedsleep spindlesand K complexes

.The former is a sudden increase in wave frequency, and thelatter is a sudden increase in wave amplitude. Stages 1 and 2are relatively "light" stages of sleep. In fact, if someone isawoken during one of these stages, he or she will often reportno being asleep at all.


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Sleep Stages: Delta Sleep, REM, and

the Sleep Cycle

Delta sleep is our deepest sleep, the point when our brain waves are least likewaking. Consequently, it is most difficult stage in which to wake sleepers, andwhen they are awakened they are usually sleepy and disoriented. Interestingly,delta sleep is when sleep walking and sleep talking is most likely to occur.

REM. This stage gets its name from the darting eye movements thataccompany it (rapid eye movement), as indicated by the EOG. Interestingly, itis also characterized by a sudden and dramatic loss of muscle tone.In fact, theskeletal muscles of a person during REM sleep are effectively paralyzed. Thisstage is also, associated with a unique brain wave pattern too, in that duringREM sleep a sleepers brain waves demonstrate characteristics that are similarto waking sleep, a combination of alpha, beta, and desynchronous waves .Most importantly to psychologists, this is the stage of sleep most associated

with dreaming. When a sleeper in a research lab begins to exhibit thephysiological indices of R.E.M sleep, and they are awakened, the great majorityof the time they will report that they were having a vivid, story-like, dream.During other stages, on the other hand, they normally do not report dreaming.


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Introducing the Doze Family


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Types Of Sleep


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Biological Clock


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Sleep Wake Meter


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Body Temperature


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Typical Sleep Cycle


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Why Sleep is Important


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Introduction to Sleep


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Adolescents


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Adults


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Older Adults


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Night Shift Work


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Sleeping Habits Related to Age


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Caffeine


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Alcohol


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Stress


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Monday Morning Blues


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Influences Affecting Sleep


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Conclusion


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DreamsAccording to Joel Achenbach in his book Why Things Are: The brain creates dreams through random electrical activity.

Randomis the key word here. About every 90 minutes the brain

stem sends electrical impulses throughout the brain, in noparticular order or fashion. The analytic portion of the brain -- theforebrain -- then desperately tries to make sense of these signals.It is like looking at a Rorschach test, a random splash of ink onpaper. The only way of comprehending it is by viewing the dream(or the inkblot) metaphorically, symbolically, since there's noliteral message.

This doesn't mean that dreams are meaningless or should beignored. How our forebrains choose to "analyze" the random anddiscontinuous images may tell us something about ourselves, just aswhat we see in an inkblot can be revelatory. And perhaps there is apurpose to the craziness: Our minds may be working on deep-seated problems through these circuitous and less threateningmetaphorical dreams.


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Similarities in DreamsHere are some other things you may have noticed about your dreams: Dreams tell a story. They are like a TV show, with scenes, characters and

props.

Dreams are egocentric. They almost always involve you. Dreams incorporate things that have happened to you recently. They canalso incorporate deep wishes and fears.

A noise in the environment is often worked in to a dream in some way,giving some credibility to the idea that dreams are simply the brain'sresponse to random impulses.

You usually cannot control a dream -- in fact, many dreams emphasize yourlack of control by making it impossible to run or yell. (However, proponents

of lucid dreaming try to help you gain control.) Dreaming is important. In sleep experiments where a person is woken up

every time he/she enters REM sleep, the person becomes increasinglyimpatient and uncomfortable over time.


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A Final Word on Sleep

How Much Sleep Do I Need?

Most adult people seem to need seven to ninehours of sleep a night. This is an average, and it is

also subjective. You, for example, probably knowhow much sleep you need in an average night tofeel your best.

The amount of sleep you need decreases with age.A newborn baby might sleep 20 hours a day. Byage four, the average is 12 hours a day. By age 10,the average falls to 10 hours a day. Seniorcitizens can often get by with six or seven hours aday.


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Tips to Improve Your Sleep

Exercise regularly. Exercise helps tire and relaxyour body.

Don't consume caffeine after 4:00 p.m. or so.Avoid other stimulants like cigarettes as well.

Avoid alcohol before bedtime. Alcohol disruptsthe brain's normal patterns during sleep.

Try to stay in a pattern with a regular bedtimeand wakeup time, even on weekends.


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Sleep Cycles & Dreams

A presentation by

Justin Chuah Jo-Han

Group 239

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JC- How Sleep Works.ppt

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