Presentation on theme: "Sound Test Circadian Pacemaker suprachiasmatic nuclei – 2 tiny clusters of neurons in front of the hypothalamus Internal and External Synchronization."— Presentation transcript:
Circadian Pacemaker suprachiasmatic nuclei – 2 tiny clusters of neurons in front of the hypothalamus Internal and External Synchronization Stages of Sleep Effects of Sleep Deprivation Dreams Examples of Sleep Disordered Breathing SDB Cardiovascular Consequences of Sleep Disordered Breathing and other causes of sleep deprivation Research into sleep function Order Out Of Chaos (ORD-14a) Sleep and the Daily Struggle for Sync @Ronnie Lemmi
Circadian Pacemaker Internal synchronization Each of the organs in the body has thousands of oscillators – similar within an organ, different across all organs all keeping 24 hour biochemical beat. Within each organ genes are active or idle at different times of day insuring that the organ’s characteristic proteins are manufactured on schedule. External synchronization 24 hour rhythm is scheduled by external synchronization – entrainment. Synchronized on 3 levels – microscopic, between organs, between our bodies and the world around us.
Light Light is the most important cue for keeping the body in sync. Light entrains the pacemaker. Light strikes the eyes and produces change in photoreceptors in the retina which forward electrical signal along the neuropathway to the suprachiasmatic nuclei in the hypothalamus. The photoreceptors include rods, cones and circadian receptors 80 % of blind people have sleep disorders 20% manage to synchronize to the light-dark cycle. Circadian photoreceptors in the retina are intact even if the rods and cones are not.
Melatonin Melatonin is a naturally occurring hormone that regulates sleepiness. It is made in the brain, to induce and maintain sleep. Peak output is in the dark of night while asleep. Decreased output when exposed to light. Siesta – Many people have a temporary drop in alertness in the early afternoon, commonly known as the "post-lunch dip." While a large meal can make a person feel sleepy, the post-lunch dip is mostly an effect of the biologic clock. People naturally feel most sleepy (have the greatest “drive for sleep”) at 2 times of the day about 12 hours apart – for example at 2:00 a.m. and 2:00 p.m. There are also 2 times when it is difficult to fall asleep even if moderately sleep deprived. These are “forbidden zones”.
Biological clock Midnight to Noon 2:00 Deepest sleep, greatest drive to sleep. Most difficult time for shift workers This has been called Zombie zone 2:00 -4:00 highest number of single vehicle accidents, births, deaths, heart attacks 4:30 People entrained to 24 hour day lowest temp 1-2 hours before time of habitual wakening. 4:00 – 6.00 Minimum temperature. Minimum alertness 6:00 Awake 6:45 Sharpest rise in blood pressure, temperature rising, cortisol “stress hormone” secreted maximally, increased alertness 7:30 Melatonin secretion stops 9:00 Highest testosterone level 10:00 High alertness 10-11 Morning forbidden zone – unlikely to be able to sleep even if sleep deprived
Biological Clock Noon to Midnight 2:00 greatest drive for sleep –siesta time. Low body temperature, low alertness. Ideal nap time 10-20 minutes. Enough time to restore concentration and improve productivity. Need to wake up before entering deep sleep otherwise it is difficult to wake up again. 2:30 Best coordination 3:30 Fastest reaction time 5:00 Greatest cardiovascular efficiency and muscle strength 6:30 Highest blood pressure 7:00 Highest body temperature, highest alertness 9:00 Melatonin secretion starts 9-10 Evening forbidden zone 1-2 hours before bedtime Even if moderately sleep deprived, difficult to fall asleep.
Stages of Sleep NREM sleep Non-Rapid Eye Movement Sleep Sleep proceeds in cycles of REM and NREM, usually four or five of them per night, the order normally being N1 → N2 → N3 → N2 → REM. There is a greater amount of deep sleep (stage N3) earlier in the night, while the proportion of REM sleep increases in the two cycles just before natural awakening
NREM Stage 1 NREM stage 1: This is a stage between sleep and wakefulness. The muscles are active, and the eyes roll slowly, opening and closing moderately. This stage is sometimes referred to as somnolence or drowsy sleep. Sudden twitches and jerks, also known as positive myoclonis may be associated with the onset of sleep during N1. Some people may also experience hypnagogic hallucinations during this stage. During N1, the subject loses some muscle tone and most conscious awareness of the external environment.
NREM Stage 2 & 3 NREM stage 2: In this stage, it gradually becomes harder to awaken the sleeper. Muscular activity decreases and conscious awareness of the external environment disappears. This stage occupies 45-55 % of total sleep in adults NREM stage 3: This stage is called slow wave sleep (SWS). The sleeper is less responsive to the environment; many environmental stimuli no longer produce any reactions.
Rapid Eye Movement Sleep REM Sleep REM is synchronized with body temp cycles. REM most likely just after temp lowest, most common at end of sleep. The sleeper now enters rapid eye movement (REM) Vivid dreams, eyes move rapidly. Breathing and heart rate fluctuate erratically, muscles are paralyzed by spinal inhibition Dreams are usually perceived more as an apparent participant than as an observer. Peak for REM early AM near end of sleep
Dreams People have proposed many hypotheses about the functions of dreaming. Sigmund Freud postulated that dreams are the symbolic expressions of frustrated desires that have been relegated to the unconscious mind. He used dream interpretation in the form of psychoanalysis to uncover these desires. Penile erections during sleep are commonly believed to indicate dreams with sexual content. In males 80% to 95% of erection accompanies REM sleep but only 12 % of men’s dreams contain sexual content.
Rapid Eye Movement Sleep REM Sleep This level is also referred to as paradoxical sleep because the sleeper, although exhibiting EEG waves similar to a waking state, is harder to arouse than at any other sleep stage. Vital signs indicate arousal and oxygen consumption by the brain is higher than when the sleeper is awake. An adult reaches REM approximately every 90 minutes, with the latter half of sleep being more dominated by this stage. REM sleep occurs as a person returns to stage N2 from a deep sleep. The function of REM sleep is uncertain but a lacks of it will impair the ability to learn complex tasks
Optimal Amount of Sleep A person's major sleep episode is relatively inefficient and inadequate when it occurs at the "wrong" time of day; one should be asleep at least six hours before the lowest body temperature. The timing is correct when the following two circadian markers occur after the middle of the sleep episode and before awakening. Maximum concentration of the hormone melatonin, and minimum core body temperature. Short sleep has been shown to be a risk factor for weight gain, hypertension and Type 2 diabetes. In terms of prevention, findings indicate that consistently sleeping around seven hours per night is optimal for health, and a sustained reduction may predispose to ill health.
Example of Sleep Disordered Breathing Obstructive Sleep Apnea (OSA) is a condition in which major pauses in breathing occur during sleep. Apneas occur when the muscles around the patient's airway relax during sleep, causing the airway to collapse and block the intake of oxygen. As oxygen levels in the blood drop, the patient then comes out of deep sleep in order to resume breathing. When several of these episodes occur per hour, sleep apnea rises to a level of seriousness that may require treatment.
Testing for obstructive sleep apnea Testing is generally performed in a sleep lab and includes: Electroencephalogram measuring brain waves. Electrocardiogram measuring heart rate and rhythm Chest bands that measure respiration Monitors that sense oxygen levels in the blood (level of oxygen may drop during apnea and rise with awakening) Body temperature recording Self administered test includes all of the above except EEG and is usually sufficient to make an accurate diagnosis. Preparation for test required. If the test is not satisfactory, a sleep lab study is usually recommended.
Treatment of Sleep Apnea Continuous Positive Airway Pressure CPAP is the most effective nonsurgical treatment for obstructive sleep apnea. It is the first treatment choice and the most widely used. Research shows that C-PAP decreases daytime sleepiness, especially in those who have moderate to severe sleep apnea. Studies show that in people who have moderate to severe sleep apnea C-PAP lowers blood pressure during both the day and the night.
Cardiovascular consequences of Sleep Disordered Breathing Hypertensive patients whose blood pressures do not fall appropriately at night, or “non-dippers,” are at increased risk for cardiovascular damage. Patients with SDB frequently have repetitive episodes of blood pressure elevation in conjunction with their apneic episodes, and they may be particularly likely to manifest a non-dipper pattern. Moreover, some individuals with SDB have hypertension that is not controlled despite the use of multiple antihypertensive. Recent data suggest that treating OSA lowers not only nighttime but also daytime blood pressure. 1
Sympathetic Nervous System The sympathetic nervous system is responsible for up- and down- regulating many homeostatic mechanisms in living organisms. Fibers from the SNS innervate tissues in almost every organ system. Best known for mediating the neuronal and hormonal stress response commonly known as the fight-or-flight response. To produce the fight or flight response, the hypothalamus activates the SNS and the adrenal-cortical system. SNS uses nerve pathways to initiate reactions in the body and the adrenal cortical system uses hormones in the blood stream. This response acts primarily on the cardiovascular system. Sympathetic stimulation can contribute to insulin resistance facilitating the development of a vicious cycle of worsening obesity, hypertension, and SDB.
Activation of the Sympathetic Nervous System Heart rate & blood pressure increase Pupils dilate Veins in skin constrict Blood glucose level increases Smooth muscles relax allowing more oxygen into lungs Non essential systems shut down (digestion) Trouble focusing on small tasks. The brain is directed to focus only on the big picture in order to determine where the threat is coming from.
Sympathetic Nervous System A major physiological result of repetitive nocturnal SDB events is intermittent, often profound hypoxemia. Intermittent hypoxia is known to activate the sympathetic nervous system both acutely and chronically. Sleep deprivation contributes to the development of insulin resistance as well as other metabolic and endocrine alterations. These observations strongly suggest sleep loss, including that attributable to SDB, has adverse effects and may represent a risk factor for obesity.
Sleep is essential for forming and consolidating memories and plays a central role in the formation of new neuronal connections. As the body sleeps the brain is actively clearing out waste material that has accumulated as a result of daily thinking. Chronic prolonged wakefulness and sleep disruption stresses the brain’s metabolism. The result is the degeneration of key neurons involved in alertness and proper cortical function and a buildup of proteins associated with aging and neural degeneration. When we skip sleep, we may be doing irreparable damage to the brain, prematurely aging it or setting it up for heightened vulnerability to other insults Article about the work of Maiken Nedergaard, a Danish biologist who has been leading research into sleep function at University of Rochester Some conclusions from her research: Good Night. Sleep Clean
Analyze your Epworth sleepiness score Interpretation 0-7: It is unlikely that you are abnormally sleepy 8-9: You have an average amount of daytime sleepiness 10-15: You may be excessively sleepy depending on the situation. You may want to consider seeking medical attention 16-24: You are excessively sleepy and should consider seeking medical attention.