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sleep

sleep  Sleep has not one main function but many.  A most popular theory on why we sleep is the restorative theory of sleep:  Restorative Theory: the theory of sleep that states that we sleep in order to replenish the processes of our minds and bodies that are depleted during the coarse of everyday life.  Increases in low wave sleep correlate with increases in physical activity  During REM sleep, proteins and other cellular components are returned to body  But is the restorative theory valid?  "Second Wind Phenomenon," the fact that people’s sleepiness disappears when they have not slept counters the restorative theory.  Studies have shown that napping or just resting in bed are equally capable of improving mood.  During Sleep: blood flow in the cerebral arteries is elevated, heart and respiration become irregular, brain activity is elevated in certain areas.  Another function of sleep is the Adaptive Non-responding Theory:  Adaptive Non-responding Theory: the evolutionary theory of sleep that suggests that sleep and inactivity at night have survival value.  Most recently (1988) Wilse Webb, one of the leading researchers on sleep for over 30 years has suggested a theory that combines the best explanatory features of the restorative and adaptive Non-responding theory.  Webb suggests that sleep is a function of sleep demand, circadian tendencies, & behaviors that promote or inhibit sleep.  Our biological clocks allow us to keep time in a changing world.  Circadian Rhythm: internal biological rhythms tied to a 24-hour day, they include endocrine activity, metabolic function and body temperature.  Alertness is lowest from midnight to 6 a.m., the time when most people are asleep.  People who work nights experience more physical problems and more stress.  The goal is to avoid, "clocks on collision," and to allow internal clocks to match external clocks, this is why night shifts are often on weekly rotation. SLEEP-WAKEFULNESS AS A CIRCADIAN RHYTHM:  Free Running Rhythms: are the natural rhythms that occur in the absence of time cues; typically running about 25 hours in humans.  An example of the detrimental consequences of the collision of external and internal clocks is jet lag.  Jet Lag: internal biological clocks collide with external clocks as a result of moving across several time zones.  Sleep is not uniform activity, but one produced of different brain waves throughout the night.  1953: Eugene Aserinsky and Nathaniel Klietman noticed periodic bursts of eye-movement during sleep.  REM Sleep (Rapid Eye-Movement Sleep): a stage of sleep associated with dreaming, and characterized by frequent eye movements, suppression of the muscles.  NREM Sleep (non-rapid eye movement sleep): all sleep occurring outside of REM sleep.  There are five stages of sleep, REM and NREM stages 1, 2, 3, & 4.  The typical sleeping pattern is 1-2-3-4-3-2-REM  Prior to Stage #1: there is a period of drowsiness in which appear alpha waves: brain wave patterns that are characteristically high frequency and low voltage (8-12 cps).  Stage #1: alpha waves are replaced by theta waves: brain wave patterns of 3-7 cps, also--- breathing and heart rate slow, muscles relax, body temperature falls. to 10 minutes later)  Stage #2: mixed EEG activity is present along with sleep spindles.  Stage #3: deepest stages of NREM sleep, occurs when 20% of brain waves are delta waves: very low frequency and high voltage brain wave patterns present in deep sleep (.5 to 2 cps)  Stage #4: recorded when 50% or more of brain waves are delta waves.  SWS (Slow Wave Sleep), Delta Sleep: the component of sleep that is defined by the inclusion of stages #3 and #4.  Paradoxical Sleep: the very deep period of REM sleep in which brain activity is high and yet extensive external stimulation is needed to move the person to a state of wakefulness.  During the night we cycle in and out of REM and NREM sleep in a 90-minute cycle, 60 minutes for human infants.  A typical night of sleep contains 4 to 6 such cycles, but distribution of REM and NREM sleep throughout the cycle changes as the night goes on.  If you sleep 8 hours, you will spend: 5% in stage 1, 50% in stage 2, 20% in stages 3+4, & 25% in REM sleep.  Hence, we spend about 2 hours dreaming each night.  During NREM Sleep: heart rate is lower and regular, body temperature is down, blood pressure is down, & oxygen consumption in the brain is lower During REM Sleep: heart rate increases and is irregular, blood pressure increases, erections or vaginal blood flow, long term memory processing, yet dramatic muscle tone suppression.  Why do some people need to sleep less than others do? These differences may be:  related to hormonal irregularity  Life expectancies for short or long sleepers are a few years less than normal.  Unfortunately in today's world, students claim that living demands of academics and social life require more hours that they have, the only way to add to the waking hours is to subtract from the sleeping hours.  Sleep Deprivation: experimental operations force an individual to remain awake, in order to determine the impact of sleep loss on a variety of physical and psychological functions.  After 2 to 3 days of such depravation, a person will engage in microsleeps: brief, 2-5 second bursts of sleep that intrude on wakefulness.  Selective sleep deprivation studies: involve the depravation of REM sleep.  The results of sleep prolonged sleep deprivation may be as dramatic as: motor and speech problems, perceptual difficulties, memory and thinking problems, or even some personality changes.  However, we recover quickly from sleep deprivation partially due to REM rebound.  REM Rebound: the body makes up for sleep deprivation of REM sleep by increasing the relative amount of REM sleep during subsequent sleep periods.  Sleeping disorders pose many threats, and are very interesting  Insomnia: the most common of all sleeping disorders is which a person has difficulty falling asleep or staying asleep.  To treat insomnia doctors may prescribe hypnotics: sleeping pills that are prescribed to promote sleep.  However the dosage needs to be systematically increased as a result of the patient’s tolerance: the body’s natural resistance to the effects of the drug and eventually, drug dependency insomnia may develop, an insomnia largely due to medication.  Learned or Conditioned Insomnia: has no symptoms because it has been acquired from their own bad sleeping habits.  Insomnia may be treated by: stimulus control therapy: here bed and bedroom are associated only with sleep; or with sleep restriction therapy: restricting a person’s time in bed in order to improve sleep efficiency.  Narcolepsy: inappropriate sleep attacks in which a person involuntarily falls asleep in the middle of a waking episode.  Narcolepsy has four main characteristic features: (1) sleep attacks; (2) cataplexy-sudden loss of muscle tone; (3) sleep paralysis; & (4) auditory, visual, or tactile hallucinations.  SIDS (Sudden Infant Death Syndrome): during sleep, a sudden inexplicable death of an infant who has been in perfectly good health.  Sleep Apnea: a rare sleeping disorder in which the person stops breathing momentarily.  Characteristically sufferers of sleep apnea are male, overweight, have high blood pressure and will experience fatigue, morning headaches, sleepiness and loss of memory but mainly FEAR of death in the night.  Somnambulism: sleep walking occurring during stage 4 sleep that usually involves repetitive acts performed while asleep that are not recalled once the person wakes.  Sleep Talking: talking occurring stage 1 of sleep, when a person is "half asleep and half awake." 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