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The Biology of Sleep
Transcript of The Biology of Sleep
June 5, 2013 The Biology of Sleep Overview What Is Sleep? REM Sleep Sleep Disorders Circadian Rhythms Not experiencing REM sleep results in mild psychological disturbances (study in 1960) Sleep's Effects Sleep's Effects Exact Definition: “Sleep is a state of physical inactivity and mental rest in which conscious awareness, thought, and voluntary movement cease and intermittent dreaming takes place" Sleep decreases consciousness and lowers metabolism Natural for humans and most vertebrates Sleep Deprivation Sleep deprivation longer than 40 hours is impossible because the body goes into brief, unpreventable microsleep Autonomic nervous system activity increases during sleep deprivation to maintain homeostasis; physical fitness cannot be maintained and immunological functions seem to suffer Sleep Onset Circadian Rhythms: biological time clocks that regulate sleep/wake cycles Degree of stimulation while one is awake affects sleep onset Lower core body temperature, good sleep environment also affect sleep patterns Sleep deprivation increases desire for sleep, linked to circadian rhythms in hypothalamus gland, which determine sleep-wake cycles, core body temperature, and other functions Stages of Human Sleep Different brain waves characterize different phases of sleep Theta waves are produced right after lying down and closing eyes; frequency of waves gets lower as one enters deeper stages of sleep Stage 1 Occurs after 15 mins of sleep, makes up 5% of sleep cycle Light, dozing sleep, irregular and fast theta waves Non-responsive but easily awakened, high chin muscle activity occurs and occasional slow rolling eye movement Stage 2 EEG measures “spindle waves” (slow electrical impulses) in bursts, brain waves slow further Introduction of K-complexes (sharp, high voltage wave groups, often followed by spindles), which may be initiated by internal or external stimuli or by an unknown source in the brain No real eye movement Makes up 45% of sleep cycle Stage 3 Very deep sleep, no eye movement, 7% of sleep cycle Theta waves have lower frequency; rapid transition to stage 4 Stage 4 Slowest brain waves, called delta waves, no eye movement, some spindles 13% of sleep cycle, the stage most affected by prior wakefulness, reflects most cerebral shutdown Researchers think this stage is most necessary for brain tissue restoration Last stage is REM sleep Throughout sleep, cycle goes 1-4, then 4-1 etc. throughout night, each cycle takes approx. 1 hour, average of 3-5 total cycles for a young adult When is it? At the end of each cycle of sleep Neural functions in brain release neurotransmitters What Are Sleep Disorders? Chronic sleep irregularities, which drastically interfere with normal nighttime sleep or daytime functioning What is it? 70 different types of sleep disorders Dreaming! As many as 30 million Americans suffer from a sleep disorder Common Sleep Disorders Insomnia Muscles are paralyzed Sufferers regularly cannot fall asleep and feel the effects the next day, as area of brain used for thinking stays activated Autonomic Activity very Irregular (unlike non REM sleep) Most deaths in sleep Drop in Amplitude, rise in frequency of brain waves Transient insomnia often caused by psychological factors such as stress, excitement, or illness or high altitude, treatable with short-term medication and relaxation techniques Issue can be with sleep onset, sleep maintenance, early arousal, light sleep, and/or conditioning Persistent insomnia a disorder, can result from medical and/or psychiatric disorders, prescription drugs, substance abuse Hypersomnia Excessive daytime sleepiness, uncontrollable sleep attacks, can fall asleep at inappropriate times Light Sleep, but difficult to awaken from Most hypersomnias (apnea and narcolepsy) associated with other disorders, so symptomatic Possible Explanations Others, like CNS hypersomnia and Kleine-Levin syndrome, are idiopathic due to unknown origin Possibly stimulus for nervous system Stimulant drugs may reduce sleepiness for brief periods, and lithium meets with some success in preventing recurrence Possibly sorting through information from life with dreams Maybe to bring oxygen to cornea of eye ( new study) Sleep Apnea Discovered in 1980s, causes irregular breathing patterns during sleep Most commonly affects middle-aged men, can cause high blood pressure and heart damage Sufferers snort or gasp and wake themselves up up to 200 times a night, causes poor night's sleep Treatments include surgery or wearing a face mask that prevents airways from collapsing during sleep Recent Research 2 types: obstructive: caused by collapse of upper airway passages; central: when diaphragm and chest muscles stop functioning briefly Narcolepsy Associated with REM sleep and central nervous system Causes frequent sleep disturbances, thus excessive daytime drowsiness Sufferers fall asleep without warning, often accompanied by cataplexy Cataplexy: muscle weakness associated with sudden emotional responses like anger, which may cause collapse Brief naps of 10 to 20 minutes may help, but there is no cure Parasomnias Events caused by physical intrusions into sleep that are thought to be triggered by the central nervous system Associated with neurological arousal mechanisms- not REM sleep so they are not the acting out of a dream Night and sleep terrors: sudden partial awakenings during non-REM sleep, subject panics, heart rate increases and pupils dilate, usually violent if awoken Dreams Affect neural connections for learning REM sleep behavioral disorder: usually elderly men, punch, kick, etc. while acting out a dream, treated easily Used to think it had to do with remembering things Sort through problems encountered during day? Sleep talking, grinding teeth, banging head, etc occur when changing sleep phases Freud says they are repressed longing Sleepwalking (Somnambulism) 30% of Americans have sleepwalked before Increased risk from sleep apnea, depression, OCD, sleeping pills, antidepressants, and other drugs, also a family history of sleepwalking Symptoms: subject may seem awake except for blank expression, seldom will respond when spoken to, difficult to awaken, sometimes bumps into objects Some sleepwalkers will perform dangerous acts, such as driving Entire episode usually lasts 10 mins, only 1 per night, and is not remembered the next day Other Sleep Disorders Restless leg syndrome (RLS): uncomfortable sensations in legs, must move/stretch, treated with drugs, cause unknown Periodic limb movement (PLM): legs and arms periodically twitch and jerk, sometimes for hours, cause unknown Both result in sleep disruptions and therefore hypersomnia Causes of Sleep Disorders Caffeine alters sleep cycles Some sleep aids may result in insomnia or daytime sleepiness Alcohol causes sleepiness but it is restless, interrupted sleep as REM sleep is affected, and alcohol withdrawal can cause nightmares. You Need Sleep! Sleep did not evolve out of laziness; it is preparation for activity Sleep also cannot be considered an indulgence, as those who sleep less lose efficiency, then have less time to sleep, etc in a cycle Social Jet Lag Social jet lag is the chronic clash between what our bodies need (more sleep) and what our lives demand (being on time) Also includes issue with different sleep amounts on weekdays and weekends Researchers found that over the last 40 years, people go to bed later, but wake up at the same time, losing 40 mins of sleep on weekdays People also spend less time outside, which may account for later circadian rhythms Delayed sleep phase syndrome: biological clock believes it is morning during night and vice-versa, causing sufferers to be tired all day Can be somewhat fixed by sleeping when tired, sleeping later, then exposing oneself to bright light when awake Channel 5TV: My Day Out with narcolepsy Part 1 Should You Use The SNOOZE Button? Lack of Sleep Causes Weight Gain For every hour of social jet lag accrued, the risk of being overweight or obese rises by about 33% Studies suggest that lack of sleep causes higher secretions of ghrelin, the appetite hormone, and a reduction of leptin, the satiety hormone (feeling full) How Much Sleep? Newborns should get about 17 hours a day 5-year-olds need about 12 hours a day Teenagers need 9.5 hours a day, though they rarely get that much Some adults only need 5-6 hours a night One must fulfill his or her own biological needs to be healthy What are they? Biological clock Body runs on a roughly 25 hour clock Body regulates its own times for sleeping and waking Other body functions are also affected to go along with sleep cycle How it works Controlled completely internally; doesn't need visual cues zeitgebers also help regulate What cues body cycle? Optic nerve sends signals to brain assist in regulation Bundle of nerves called the suprachiasmatic nucleus, in the brain's hypothalamus Brain coordinates clocks throughout the body Rewound each night by sleep How do they get out of rhythm? Imposed 24 hour clock must be adjusted to Difficult to adjust to more than 1 hour change (jet lag) People who work at night still experience less alertness at night because of visual cues Melatonin What is it? Primary Regulatory Hormone of human sleep Initiating and maintaining sleep Levels peak at about 2 am Exposure to light regulates its release How is it made? Pineal Gland (part of neuroendocrine system) Nerve fibers in pineal gland release noradrenalin, a chemical messenger produced by the nervous system, which stimulates pinealocytes to produce and release melatonin Very low levels during day, made at like 9 or 10 at night Tryptophan is converted to it in pineal gland Levels at different times vary throughout life and between different people What does it do? Can be ingested for various purposes Insomnia? Jet lag? Improve sleep? Cancer? Less concentration and slower reaction, lowers body temperature, causes vasoconstriction, boosts natural killer cells action, Research on Dreams David Maurice hypothesizes that while humans sleep, rapid eye movement occurs to supply much need oxygen to the cornea of the eye Aqueous humor needs to be stirred Not enough oxygen by diffusion as had been assumed Dreams are random nervous system stimuli In 1983, Nobel laureate Francis Crick and his Salk Institute colleague Graeme Mitchison wrote a Nature article, dreams are cognitive debris Disproves other theories Increase in Sleep Research In 1929, German psychiatrist Hans Berger invented the electroencephalograph, which senses and records signals from the brain’s electrical activity Records electrical charges from neurons Since then, a lot more sleep research! Works Cited
Breecher, Maury M., M.P.H., Ph. D. "The Biology of Dreaming: A Controversy That Won't Go to Sleep." The Biology of Dreaming. Columbia University, n.d. Web. 24 May 2013.
Carter, Michael D., and David N. Juurlink. "Melatonin." CMAJ: Canadian Medical Association Journal 20 Nov. 2012: 1923. Science In Context. Web. 3 June 2013.
Kalb, Claudia. "Social jet lag." Smithsonian Jan. 2013: 15. Science In Context. Web. 3 June 2013.
Lloyd, Janice. "Sleepwalking is fairly common, study finds." USA Today 15 May 2012: 03A. Science In Context. Web. 3 June 2013.
"Melatonin." Drugs and Controlled Substances: Information for Students. Ed. Stacey L. Blachford and Kristine Krapp. Detroit: Gale, 2010. Science In Context. Web. 3 June 2013.
Obringer, Lee Ann. "How Dreams Work." HowStuffWorks. HowStuffWorks.com, 27 Jan. 2005. Web. 20 May 2013.
"Polysomnograph." The Gale Encyclopedia of Science. Ed. K. Lee Lerner and Brenda Wilmoth Lerner. 4th ed. Detroit: Gale, 2010. Science In Context. Web. 3 June 2013
"Sleep." World of Health. Gale, 2007. Science In Context. Web. 3 June 2013
"Sleep and sleep disorders." UXL Encyclopedia of Science. U*X*L, 2007. Science In Context. Web. 3 June 2013.
"Sleep disorders." The Gale Encyclopedia of Science. Ed. K. Lee Lerner and Brenda Wilmoth Lerner. 4th ed. Detroit: Gale, 2008. Science In Context. Web. 3 June 2013.
The New Frontier! There is still a lot to learn about sleeping and dreams! Up-and-coming field of science A ton is being learned and field is expanding!