Night sleep Night sleep Scientific facts By Prof. Afaf El-Ansary.

Night sleepNight sleep

Scientific factsScientific factsByBy

Prof. Afaf El-AnsaryProf. Afaf El-Ansary

Information about sleepInformation about sleep Sleep is a behavioral state that is a natural part of Sleep is a behavioral state that is a natural part of

every individual’s lifeevery individual’s life. . We spend about oneWe spend about one--third of our lives asleepthird of our lives asleep. . Sleep is a required activity, not an optionSleep is a required activity, not an option. . sleep is important for normal motor and cognitive sleep is important for normal motor and cognitive

functionfunction. . We all recognize and feel the need to sleepWe all recognize and feel the need to sleep. . After sleeping, we recognize changes that have After sleeping, we recognize changes that have

occurred, as we feel rested and more alertoccurred, as we feel rested and more alert. . Sleep actually appears to be required for survivalSleep actually appears to be required for survival. .

Rats deprived of sleep will die within two to three Rats deprived of sleep will die within two to three weeks, a time frame similar to death due to weeks, a time frame similar to death due to starvation.starvation.

Why SleepWhy Sleep??

11. . Sleep is essential for normal Sleep is essential for normal function and even survival. function and even survival.

22. . Possible reasons for sleep usually Possible reasons for sleep usually involve some involve some ""recoveryrecovery" " process. process.

aa. . Tissue repair.Tissue repair. bb. . Resting the body and brain. Resting the body and brain. cc. . Brain anabolism Brain anabolism ((ee..gg.., synthesis of , synthesis of

glycogenglycogen). ). dd. . Consolidation of memory and daily Consolidation of memory and daily

experiences.experiences.

SleepinessSleepiness Problem sleepiness may be associated with:Problem sleepiness may be associated with: difficulty concentrating,difficulty concentrating, memory lapses,memory lapses, loss of energy, loss of energy, fatigue, lethargy, fatigue, lethargy, and emotional instabilityand emotional instability. .

Lifestyle factors and undiagnosed or Lifestyle factors and undiagnosed or untreated sleep disorders can cause untreated sleep disorders can cause problemproblem

The Biological clockThe Biological clock

The activity of this clockThe activity of this clock makes us sleepy at nightmakes us sleepy at night and awake during the day.and awake during the day. Our clock cycles with an Our clock cycles with an approximately24-hour periodapproximately24-hour period and is called a and is called a circadiancircadian clock. clock.

Location of the circadian Location of the circadian clockclock

In humans, this clock is located in the In humans, this clock is located in the suprachiasmatic nucleus (SCN).suprachiasmatic nucleus (SCN). The The SCN is actually a very small structure SCN is actually a very small structure consisting of a pair of pinhead-size consisting of a pair of pinhead-size regions, each containing only about regions, each containing only about 10,000 neurons out of the brain’s 10,000 neurons out of the brain’s estimated 100 billion neurons.estimated 100 billion neurons.

Because of your biological clock, you Because of your biological clock, you naturally feel the most sleepy naturally feel the most sleepy between midnight and 7 abetween midnight and 7 a..mm. .

Your biological clock makes you the Your biological clock makes you the most alert during daylight hours and most alert during daylight hours and the most drowsy in the early morning the most drowsy in the early morning hourshours. . Consequently, most people do Consequently, most people do their best work during the daytheir best work during the day..

Our biological clock which controls Our biological clock which controls our sleepour sleep//wake cycle will attempt to wake cycle will attempt to function according to a normal function according to a normal dayday//night schedule even when we try night schedule even when we try to change it.to change it.

55

The cue that synchronizes the The cue that synchronizes the internal biological clock to the internal biological clock to the environmental cycle is lightenvironmental cycle is light..

PhotoreceptorsPhotoreceptors in the retina in the retina transmit light-dependent signals to transmit light-dependent signals to the SCN. the SCN.

Misconceptions about SleepMisconceptions about Sleep Sleep is time for the body in general and the brain Sleep is time for the body in general and the brain

specifically to shut down for rest.specifically to shut down for rest.

Getting just one hour less sleep per night than needed Getting just one hour less sleep per night than needed will not have any effect on daytime functioning.will not have any effect on daytime functioning.

The body adjusts quickly to different sleep schedulesThe body adjusts quickly to different sleep schedules..

People need less sleep as they grow older.People need less sleep as they grow older.

““good night’s sleep” can cure problems with good night’s sleep” can cure problems with excessive daytime sleepiness. excessive daytime sleepiness.

Phases of night sleepingPhases of night sleeping

There are 4 phases:There are 4 phases: W1………awake eyes openW1………awake eyes open

W2……….awake, eyes closedW2……….awake, eyes closed

S1………...Sleeping phase IS1………...Sleeping phase I

S2………..Sleeping phase IIS2………..Sleeping phase II

Stages of sleepStages of sleep

Two basic stages, or states, of sleep:Two basic stages, or states, of sleep:

Non rapidNon rapid eyeeye movementmovement ( (NREM.NREM.

andand rapidrapid eyeeye movementmovement ( (REM.REM. As the night progresses, however, As the night progresses, however,

the amount of deep NREM sleep the amount of deep NREM sleep decreases and the amount of REM decreases and the amount of REM sleep increasessleep increases..

The function of organs during the sleep The function of organs during the sleep cyclecycle

The Endocrine SystemThe Endocrine System Sleep is one of the events that modify the timing of Sleep is one of the events that modify the timing of

secretion for certain hormonessecretion for certain hormones. . Many hormones are Many hormones are secreted into the blood during sleepsecreted into the blood during sleep..

** The release of The release of growth hormonegrowth hormone is related in part to repair is related in part to repair processes that occur during sleep.processes that occur during sleep.

**Follicle stimulating hormoneFollicle stimulating hormone andand luteinizing luteinizing

hormonehormone, , which are involved in maturational and which are involved in maturational and reproductive processes, are among the hormones released reproductive processes, are among the hormones released during sleepduring sleep. .

**ThyroidThyroid--stimulating hormonestimulating hormone, are released prior to sleep, are released prior to sleep. .

Renal systemRenal system Kidney filtration, plasma flow, and Kidney filtration, plasma flow, and

the excretion of sodium, chloride, the excretion of sodium, chloride, potassium, and calcium all are potassium, and calcium all are reduced during both NREM and REM reduced during both NREM and REM sleepsleep. . These changes cause urine to These changes cause urine to be more concentrated during sleepbe more concentrated during sleep. .

The digestive systemThe digestive system

Alimentary activityAlimentary activity. . In a person with In a person with normal digestive function, gastric normal digestive function, gastric acid secretion is reduced during acid secretion is reduced during sleepsleep. . In those with an active ulcer, In those with an active ulcer, gastric acid secretion is actually gastric acid secretion is actually increased and swallowing occurs less increased and swallowing occurs less frequentlyfrequently. .

Body temperatureBody temperature Another interesting rhythm that is Another interesting rhythm that is

controlled by the biological clock is the controlled by the biological clock is the cycle of body temperature, which is lowest cycle of body temperature, which is lowest in the biological night and rises in the in the biological night and rises in the biological daytimebiological daytime. . This fluctuation This fluctuation persists even in the absence of sleeppersists even in the absence of sleep. . Activity during the day and sleep during Activity during the day and sleep during the night reinforce this cycle of changes in the night reinforce this cycle of changes in body temperature.body temperature.

Melatonin secretionMelatonin secretion

The release ofThe release of melatoninmelatonin, , a a hormone produced by the pineal hormone produced by the pineal gland, is controlled by the circadian gland, is controlled by the circadian clock in the SCNclock in the SCN. . Its levels rise during Its levels rise during the night and decline at dawnthe night and decline at dawn. . Melatonin has been called the Melatonin has been called the hormone of darkness because of this hormone of darkness because of this patternpattern. .

How to increase melatonin How to increase melatonin secretionsecretion

Keep you mealtimes as regular as Keep you mealtimes as regular as possible to keep your body in sync possible to keep your body in sync with the rhythms of the day.with the rhythms of the day.

Keep your diet light at nightKeep your diet light at night..

Avoid stimulants.Avoid stimulants.

Avoid exercising late at nightAvoid exercising late at night..

MM

Sleep & Chronophysiology

Laboratory

How much sleep do you How much sleep do you needneed??

Not everyone needs the same Not everyone needs the same amount of sleep Natural short amount of sleep Natural short and long sleepersand long sleepers

BUTBUT sleeping less than 6.5 or sleeping less than 6.5 or more than 9 hours is associated more than 9 hours is associated with 1.7 x greater mortality & with 1.7 x greater mortality & risk of disease.risk of disease.

Consequences of Sleep LossConsequences of Sleep Loss

Poor academic performance correlated Poor academic performance correlated with insomnia & poor sleep qualitywith insomnia & poor sleep quality

Automobile Accidents: Fatigue is a Automobile Accidents: Fatigue is a leading cause leading cause

Minor medical Illness: Cold & Flu rates Minor medical Illness: Cold & Flu rates higher in poor sleepershigher in poor sleepers

Circadian dysregulation: Creating Jet Lag Circadian dysregulation: Creating Jet Lag in the home environmentin the home environment

Psychiatric Illness: Psychiatric Illness: Depression & AnxietyDepression & Anxiety

MMSleep &

Chronophysiology Laboratory

AdenosineAdenosine Adenosine release in the brain may occur Adenosine release in the brain may occur

when energywhen energy--storing molecules containing storing molecules containing adensosin triphosphate adensosin triphosphate ((ATPATP) ) are broken are broken down to provide energy for cell activitydown to provide energy for cell activity. . When brain cells burn ATP, adenosine When brain cells burn ATP, adenosine builds upbuilds up. . The longer humans are awake, The longer humans are awake, the higher the levels of this chemical in the higher the levels of this chemical in their brainstheir brains. .

Interleukin and HistamineInterleukin and Histamine

A compound called interleukin, A compound called interleukin, present in cells all over the body, present in cells all over the body, may foster the sleepiness associated may foster the sleepiness associated with infection and inflammation.with infection and inflammation.

Another brain chemical, histamine, Another brain chemical, histamine, may promote wakefulness with an may promote wakefulness with an input into the hypothalamus and input into the hypothalamus and possibly to cpossibly to c--fos cellsfos cells. .