Lecture 8 - Sleep PDF

CIRCADIAN RHYTHMS AND SLEEP Roadmap Module 1- Circadian rhythms and Module 1- Circadian rhythms: Sleep and wakefulness cycles adenosine Module Module 2-2-Sleep, Sleep,stages stagesofofsleep sleep Module 3-3-Why...

CIRCADIAN RHYTHMS AND SLEEP Roadmap Module 1- Circadian rhythms and Module 1- Circadian rhythms: Sleep and wakefulness cycles adenosine Module Module 2-2-Sleep, Sleep,stages stagesofofsleep sleep Module 3-3-Why Module doare What we the sleep? brain mechanisms of sleep and wakefulness? Module 4- Chronotypes: When is your Module 4-Why do we sleep? Why do we dream? peak of wakefulness Module Module 5-5-Sleep Chronotypes: loss When is your peak of wakefulness Module 6- Sleep disorders Module 1 Circadian rhythms and adenosine FLUCTUATIONS IN THE ENVIRONMENT Biological Rhythms Endogenous biological rhythms that help us deal with fluctuations in the environment. Linked to the cycle of: Hibernation Days- CIRCADIAN RHYTHM (e.g. wakefulness and sleep) Seasons- CIRCANNUAL RHYTHM (e.g migration) Migration Human Circadian rhythms Endogenous (generated from within) rhythms control or initiate various biological processes. Regulate the sleep/ wake cycle. Also regulate other processes such as: the frequency of eating and drinking, body temperature, secretion of hormones, volume of urination, and sensitivity to drugs. Human Circadian Rhythms  What gives rise to biological rhythms? Neural system that times behavior Suprachiasmatic nucleus (SCN) Rhythms of Waking and Sleep Light resets the SCN via a small branch of the optic nerve known as the retinohypothalamic path (from the retina in your eye to the hypothalamus). If light is available, this pathway signals the SCN that it still not time to sleep. Is it possible that your smart phones and tables are disrupting your sleep? Smart phones and sleep Smartphones—like laptops, tablets, and televisions—emit something called blue light, which is a type of light that the brain interprets as daylight. The blue light actually suppresses melatonin (a hormone that affects circadian rhythm and should increase when you are preparing for bedtime). The result: Your brain feels stimulated. This is fine if you’re looking at your smartphone’s screen at noon, but if you’re looking at the screen at midnight, your brain is going to get confused and think that the sun is out— making it even tougher to fall asleep. Sleep pressure: adenosine  Sleep pressure- Adenosine Sleep pressure is the desire to sleep Correlated with the amount of adenosine in your brain You can think of adenosine as the chemical barometer that will continuously register the amount of elapsed time since you woke up this morning. Adenosine does 2 things: Turns down the volume of wake- promoting regions in the brain Turns on the volume of sleep- promoting regions in the brain.  Sleep pressure- Adenosine When adenosine concentrations peak, you will feel an irresistible urge to sleep. If we wake up at the same time during the week but sleep in on the weekend, it might be difficult to fall asleep on Sunday night. Not enough hours have gone by for enough adenosine to build up. Taking a long nap in the afternoon will reduce the levels of adenosine in the afternoon and might make it difficult to fall asleep at night.  Adenosine and Caffeine Caffeine blocks the adenosine receptor- tricks the brain by muting the adenosine signal. The half-life of caffeine is 6 hours (how long it takes the body to remove 50% of the caffeine concentration. The quarter-life of caffeine is 12 hours. If you take a coffee or tea at 7:30 pm, by 1:30 am you still have 50% of the caffeine in your system. Foods like dark chocolate and ice- cream also have significant amounts of caffeine. Circadian rhythms and sleep pressure  16 Module 2 Sleep Scientist don’t fully understand the role of sleep. However, mysteries about sleep have just started unraveling in sleep laboratories around the world.  17 Measuring sleep: electroencephalogram An electroencephalogram (EEG) is a test that detects electrical activity in your brain using small, metal discs (electrodes) attached to your scalp. Your brain cells communicate via electrical impulses and are active all the time, even when you're asleep. This activity shows up as wavy lines on an EEG recording  18 Stages of sleep Non-REM Sleep Consists of 4 stages: Stage 1 Stage 2 Stage 3 Stage 4 REM- sleep (rapid eye movement or paradoxical sleep)  19 90-Minute Cycles During Sleep With each 90-minute cycle, stage 4 sleep decreases and the duration of REM sleep increases.  20 REM Sleep- Paradoxical sleep Rapid-eye-movement (REM sleep) Also called paradoxical sleep because the brain waves resemble the activity of the awake brain. Atonia No tone; complete muscle inactivity produced by the inhibition of motor neurons; no movement of the body except for eyes Vivid dreams occur during REM sleep Everyone dreams a number of times each night Dreams appear to take place in real time, and dream sessions get longer as a sleep session progresses  21 Non-REM Sleep Also called slow-wave-sleep (SWS). Dreaming is rare during NREM sleep (but it happens) Muscles are not paralyzed. Muscles maintain muscle- tone. Sleeptalking, sleepwalking, night terrors After sleep deprivation there is usually a sharp rebound of SWS, suggesting there is a "need" for this stage Non-REM sleep REM sleep Four stages One stage Synchronized/slow Desynchronized and brain activity (Slow fast brain activity wave sleep SWS) (Paradoxical sleep) Not-vivid dreams Vivid dreams Muscle tone Atonia Posture maintained Posture completely lost Decreased as night Increases as night progresses progresses Entire body moves Eye movement Module 3 Why do we sleep?  24 Why do we sleep? The short answer is, no one knows Some hypothesis: Protective role in human evolution- sleep emerged in evolution to preserve energy and protect us during the time of day when there is little value and considerable danger. When darkness shut down the day’s hunting, food gathering and travel, our distant ancestors were better off asleep in a cave, out of harm’s way. Those that didn’t try to navigate around dark cliffs were more likely to leave descendants.  25 Why do we sleep? Restoration theory –sleep restores the immune system and repair body and brain tissue. Studies in mice show that sleep sweeps the brain of toxic metabolic waste products. Scientist are investigating if lack of sleep might lead to the development of Alzeihmer’s disease (accumulation of brain proteins proteins).  26 Why do we sleep? Memory consolidation from short-term memory into long-term memory. Short-term memories are memories that last a few second or a few minutes. Long-term memories are long-lasting memories. Experiences of the day are often replayed during sleep, strengthening those brain connections and making them more long-lasting. http://www.pbs.org/wgbh/nova/sciencenow/3410/01.html (PBS) Module 4 When is your peak of wakefulness? Chronotypes Some of us are more alert and active in the morning, some of us in the middle of the day and some of us in the evening. These differences affect when we feel tired and when we are able to sleep. These individual differences in circadian typology are referred to as chronotypes. Chronotypes Morning type-larks (40%) Prefer to wake up with the sun Feel more energetic earlier in the day. Night owls (30%) Prefer going to bed late and wake up late (even in the afternoon) Some are unable to fall asleep early at night, no matter how hard they try. Peak of productivity later in the day. Unable to function well early in the morning- early in the morning their prefrontal cortex remains in a disabled state. In-between types (30%) Chronotypes Strongly determined by genetics. Chronotypes are not a choice – morning larks or night owls are not larks or owls by choice. Society and chronotypes Society largely rewards early types. Many jobs start early. Job performance of owls as a while is far less optimal in the morning. Owls are more chronically sleep deprived. Sleep deprivation leads to worse health” depression, anxiety, diabetes, cancer, heart attach and stroke. Need for a change? Circadian rhythms of teenagers The circadian rhythm of teenagers shifts. Children and older adults have internal clocks set to make them sleepy in the evening, around 8 or 9 p.m. This shifts to 10 or 11 p.m. in puberty. Teenagers are biologically programmed to go to sleep later. Careful: Do not take this to mean that you should stay longer on your phones. High school start times not consistent with this shift. Circadian rhythms of teenagers In 2014 the American Academy of Pediatrics issued a statement that asked that schools start at 8:30 a.m. or later. https://pediatrics.aappublications.org/content/pediatrics/134/3/642.full. pdf Circadian rhythms of teenagers The American Academy of Pediatrics issued a statement that asked that schools start at 8:30 a.m. or later. Only 14% of schools comply with this. As a result, many teenagers in the United States suffer from sleep deprivation. 28% of high school students acknowledged falling asleep in class at least once a week (Sleep foundation, 2006). 69% of college and university students reported “feeling tired” or “having little energy” on several or more days in the last two weeks (APA, 2009). Module 5 Sleep loss  Prevalence of short sleep duration Short sleep duration is defined as less than 7 hours of sleep per 24-hr period. Consequences of sleep deprivation Sleep and well-being WASHINGTON, D.C. -- Americans who report that they usually get more hours of sleep per night have higher overall well-being than those who typically get fewer hours of shut-eye. Getting more hours of sleep is positively associated with having higher well-being, with the relationship peaking at eight hours and leveling off thereafter. These data are based on interviews with 7,058 U.S. adults conducted Sept. 5-19, 2014, as part of the Gallup-Healthways Well-Being Index. The Well-Being Index measures five elements of well-being: purpose, social, financial, community and physical. Sleep deprivation and performance Sleep deprivation and academic performance Sleep-deprived students often function below their peak. Sleep deprivation diminishes productivity (leads to more hours needed to fulfill school requirements) ability to concentrate (leads to reduced ability to study) increases the tendency to make mistakes (leads to more errors in exams) affects memory consolidation Sleep deprivation and reaction times Slow responses for those operating equipment, piloting or diving. Increased errors in visual attention tasks (reading X-rays, performing surgery. Driver fatigue has contributed to an estimated 20% of American traffic accidents. Sleep deprivation and obesity Sleep deprivation: Increases ghrelin, a hunger arousing hormone Decreases leptin, a satiety hormone Increases cortisol, a stress hormone that stimulates the body to make fat Lack of sleep and depression Sleep loss is a predictor of depression. In a study of 15,500 subjects between 12 and 18 years old found that those who slept 5 or fewer hours a night had a 71 % higher risk of depression than their peers who slept 8 hours or more (Gangwisch et al., 2010). Lack of sleep and mood Lack of sleep leads to irritability. For students, lack to sleep leads to more conflicts in friendships and romantic relationships. Do you sleep enough? How much sleep do we really need? How much sleep do we really need? Are you productive, healthy and happy on seven hours of sleep? Or does it take you nine hours of quality ZZZs to get you into high gear? Do you depend on caffeine to get you through the day? Do you feel sleepy when driving ? Do you have health issues such as being overweight? Are you at risk for any disease? Imagine that I could give you a medicine that: Improves your mood and decreases the likelihood of depression Improves your ability to concentrate Improves your grades at school Reduces the number of errors that you make and the likelihood of car accidents Helps you control your weight Improves your immune system and helps you battle disease Reduces your irritability Reduces your conflicts with friends and family Makes you feel more rested Increases your feelings of well-being That medicine is free and you can have it tonight Sleep  Sleep is NOT a luxury It is as vital to health and well-being as food and exercise For more information on sleep National sleep foundation https://sleepfoundation.org/