Understanding Sleep Stages and Common Disorders, Lecture notes of Psychology

Download Understanding Sleep Stages and Common Disorders and more Lecture notes Psychology in PDF only on Docsity! OAC: Stage 2 Psychology What are the stages of sleep? There are five stages of sleep: stages 1, 2, 3, 4 and REM (rapid eye movement). The body cycles through the different sleep stages from stage 1 to REM and then begins again with stage 1. Each stage represents a different physical and mental state of the body during sleep. During some stages, the body is in a lighter sleep and can be awakened more easily, while others indicate a very deep sleep.  Stage 1 (Drowsiness) – We drift in and out of sleep for about 5 to 10 minutes and can be awakened easily. Our eyes move very slowly and muscle activity slows.  Stage 2 (Light Sleep) – Our eye movements stop and our brain waves (fluctuations of electrical activity that can be measured by electrodes) become slower, with occasional bursts of rapid waves called sleep spindles. Our heart rate slows and body temperature decreases.  Stages 3 and 4 (Deep Sleep) – Slow brain waves called delta waves begin to appear, interspersed with smaller, faster waves. By Stage 4 the brain produces delta waves almost exclusively. It is very difficult to wake someone during stages 3 and 4, which together are called deep sleep. There is no eye movement or muscle activity. People awakened during deep sleep do not adjust immediately and often feel groggy and disoriented for several minutes after they wake up. Some children experience bedwetting, night terrors, or sleepwalking during these stages.  REM Sleep – During REM sleep, our breathing becomes more rapid, irregular, and shallow, our eyes jerk rapidly in various directions, and our limb muscles become temporarily paralyzed. Our heart rate increases, our blood pressure rises, and males develop penile erections. People dream during this stage. The average length of time for a complete sleep cycle is 90-110 minutes. About 50 percent of sleep time is spent in stage 2 and about 20 percent in REM sleep. The remaining 30 percent is split among the other stages. On average, a person will cycle through the stages 4 or 5 times in an eight hour period. After a person falls asleep, the first REM sleep period generally happens 70-90 minutes later. The first cycles of the night will tend to have shorter REM periods and longer periods of deep sleep. This trend reverses as the night goes on. The later cycles have longer REM periods and shorter deep sleep periods. By morning, most sleepers spend almost all of their time in stages 1, 2 and REM sleep with very little or no deep sleep (stages 3 and 4). Infants are unique in that they spend approximately 50 percent of their sleep time in REM sleep. OAC: Stage 2 Psychology Common Sleep Disorders Insomnia – Insomnia can be either those people who have reduced sleep quality and quantity and those who have impaired daytime functioning. To classify insomnia you need to distinguish between primary and secondary insomnia. Primary insomnias are disorders that exist on their own. Secondary insomnias are those that occur in the presence of another mental, medical or sleep disorder. Insomnia is prevalent in the community → 15-35% of population report acute insomnia (less than 2 wks of symptoms) → 9-12% of population report chronic insomnia (more than 1 month of symptoms) Sub groups most at risk → elderly, females, shiftworkers, those with obsessive and anxious personalities, medical conditions, psychiatric conditions Excessive daytime sleepiness - An important sleep disorder that leads to excessive daytime sleepiness is obstructive sleep apnea syndrome. Sleep apnea is when an individual stops breathing during sleep. In its mild form it results in snoring. Apnea results in decreased blood oxygen levels and the body’s defence mechanism is to arouse the person, therefore restoring the breathing. A person with apnea repeats episodes of apnea followed by an arousal with loud snorts and then a return to sleep. This may happen up to 400 times a night. → the apnea sufferer is usually unaware of their disorder → it can lead to daytime sleepiness, reduced cognitive performance and learning → 8-20% of population are chronic snorers → 1-4% have obstructive sleep apnea (it is especially prevalent in overweight males) Parasomnias This disorder can include sleep walking, night terrors, and nightmares. They are most common in children. Night terrors and sleep walking occur in slow wave sleep (stage 4). Nightmares occur during REM sleep. Generally the frequency of these decrease with a person’s age. Circadian-related sleep disorders A subset of insomnias that occur because of problems with the timing of sleep with respect to the day-night cycle. → Jet lag, shift work