SLEEP Dr. Libby Dunphy Honors 200-01
Outline What is sleep? Why do we sleep? How much sleep is needed? How do Circadian Rhythms work?
What is Sleep?
Discuss with neighbors 1) What is sleep? What are some characteristics of sleep? 2) Work together to compose a definition of sleep for a dictionary.
What is Sleep? Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles http://en.wikipedia.org/wiki/sleep Recurring =? Consciousness =? Sensory activity =? Voluntary muscles =?
"Early to bed, and early to rise, makes a man healthy, wealthy, and wise. --- Benjamin Franklin, inventor "Sleep is an acquired habit. Cells don't sleep. Fish swim in the water all night. Even a horse doesn't sleep. A man doesn't need any sleep." --- Thomas Edison, inventor
Who Sleeps? all mammals, all birds, and many reptiles, amphibians, and fish
Animal sleep habits Brown Bat 19.9 hours (83%) Python 18 hours (75%) Tiger 15.8 hours (66%) Three-toed Sloth 14.4 hours (60%) Cat 12.1 hours (51%) African Elephant 3.3 hours (14%) Giraffe 1.9 hours (8%)
Comparison of sleep time
Animal Sleep Unihemispheric sleep Some animals let half their brain sleep while the other half stays awake. Some birds, reptiles Many aquatic mammals
Discuss with neighbors 1) Animals cannot defend themselves while asleep! Wouldn t evolution get rid of sleep if it caused an animal to get eaten? 2) Why do animals need to sleep? How is sleep useful? What purposes does it serve? 3) What happens when an animal (or human) doesn t sleep enough?
Sleep is Essential ALL animal species sleep. ALL animals need recovery sleep when they stay awake longer than usual. ALL animals suffer serious consequences when they lack sleep. http://en.wikipedia.org/wiki/sleep
Sleep is Essential Rats (normally live 2-3 years) Deprived of REM sleep die in 5 weeks Deprived of all sleep die in 3 weeks http://parishotelboutique.blogspot.com/2011/01/happy-monday.html
Why do we Sleep? help conserve energy decreases metabolism only about 5 10% Other reasons??? Physical well-being (illness recovery, etc) Mental well-being (stress reduction) Cognition and Problem solving
Sleep in Human Animals
Human sleep Average adult needs 7-8 hours sleep a day 1/3 of your life is spent asleep 122 days of the year If you live 75 years, 25 years of that will have been spent asleep. Dreaming occurs 5 times in an 8 hour period That is 1,825 dreams a year!
Why do we sleep? "As far as I know, the only reason we need to sleep that is really, really solid is because we get sleepy. William Dement, founder of the Sleep Research Center at Stanford University
Discuss with neighbors 1) How much sleep is enough for someone your age? 2) How much sleep do you get on an average night? 3) Do you think you get enough sleep? 4) If it s not enough sleep, do you think that you are impaired in any way by being tired? 5) If you could sleep as much as you needed, how many hours do you think you would sleep?
Sleep Deprivation Too little sleep results in: Impaired memory Depression Decrease immune system (illness, infection) Increased pain http://www.webmd.com/
Sleep Deprivation http://insomnia.ygoy.com/2011/01/03/lack-of-sleep-side-effects/
Sleep is Essential Humans Longest record time without sleep is 11 days Rare sleep disorders cause longer periods Microsleep (short loss of consciousness) Progressive problems Concentration Motivation Perception Hallucination
Sleep Heals Sleep deprivation causes slower wound healing in rats Decreases the number of white blood cells
Sleep Heals Study: people who averaged <7 hrs/night were about 3x more likely to develop cold symptoms than study volunteers who got >8 hrs/night (when exposed to rhinovirus) In addition, those individuals who got better quality sleep were the least likely to come down with a cold.
Sleep Reduces CV Risk Study : -even modestly reduced sleep (six to seven hours per night) was associated with a greatly increased the risk of coronary artery calcification (clogged arteries), a predictor of future myocardial infarction (heart attack)
Sleep improves memory Sleep Deprivation causes A decrease in working memory (holds information in the mind so it can be used for tasks) A decrease in higher-level cognitive functions including decision making and reasoning
Sleep and Memory http://healthysleep.med.harvard.edu/healthy /matters#link12
Sleep and Obesity Study #1: -people who slept <6 hrs/ night were much more likely to have excess body weight -people who slept 8 hrs/ night had the lowest body fat Study #2: -babies who are "short sleepers" are much more likely to develop obesity later in childhood
Sleep and Obesity http://ahnutrition.wordpress.com/2009/07/30/lack-sleep-weight-gain/
http://news.stanford.edu/news/2004/december8/med-sleep-1208.html
Circadian Rhythms Circa (around) Diem (day) Biological process that displays an oscillation of about 24 hours Circadian clock found in animals, plants, and fungi (even some bacteria!) Controlled by external cues (zeitgebers), most importantly daylight
http://en.wikipedia.org/wiki/file:biological_clock_human.svg
Control of Circadian Rhythms Light turns on photosensitive ganglion cells in the retina (back of eye) The eye sends a signal to the SCN (in the hypothalamus region of brain) The SCN sends a signal to the Pineal gland which makes melatonin
Light input on circadian rhythms
Melatonin levels http://www.epgonline.org/
Melatonin Melatonin levels rise in the evening and drop towards morning. Binds to melatonin receptor found in brain and other tissues Causes drowsiness and sleep Has been used to treat insomnia, jetlag, autism, cancer, Alzheimers, etc
Testing your Reaction Time http://healthysleep.med.harvard.edu/needsleep/whats-in-it-for-you/how-awake-are-you
A culture of sleep deprivation I burn my candle at both ends, It will not last the night. But ah, my foes, and oh, my friends, It gives a lovely light. -Edna St. Vincent Millay
Discuss with neighbors 1) Does the American culture value sleep? 2) Do other cultures value sleep? 1) Imagine if a friend tells you that she sleeps 11 hours a day. What would you think about her? 2) Imagine if a friend tells you that she sleeps 4 hours a day. What would you think about her?
WIRED AND TIRED http://www.eurofound.europa.eu/ewco/2004/10/fi0410nu01.htm
What s to blame? Before electric lights Segmented sleep was normal??? Sleep from sunset until midnight Period of wakefullness- Sex, prayer, thought Second sleep until dawn Siesta or nap during daytime After electric lights One long sleep from late in evening until morning
WIRED AND TIRED 1990-24% of Americans get less than 6 hrs / night 2010-30% of Americans get less than 6 hrs / night 74% of Americans drink a caffeinated beverage on an average workday
Discuss with neighbors 1) Do you think that you get less sleep than your parents did at your age? 2) Why don t you get enough sleep? What factors are different now compared to 20 years ago?