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2. A number of biological
processes follow regular rhythms or cycles that
vary in length. The study of biological rhythms,
chronobiology, includes research on the effects
of such cycles on the diagnosis and treatment of
diseases.
3. Circadian rhythms are biological changes that occur on a daily schedule, including the sleep-wake cycle and the body temperature cycle.
4. Circadian rhythms are controlled by the suprachiasmatic nucleus (SCN), neurons located in the hypothalamus that act as an internal clock. Levels of a hormone secreted by the pineal gland, melatonin, are affected by light and darkness; thus melatonin may play a role in controlling biological rhythms. By isolating volunteers in an environment without time cues, researchers have found that the free-running sleep-wake cycle extends to about 25 hours. To correspond to the 24-hour day, the cycle must be reset every day by external cues, especially sunlight.
5. Jet travel and shift work can disrupt the sleep-wake cycle. The symptoms of jet lag result from the difference between our internal clock and the time in our environment. It is easier to adapt to phase delays, resulting from east -west travel, than to phase advances, resulting from west-east travel.
6. Rotating shift work can be improved by clockwise rotation (days to evenings to nights) and keeping workers on a given shift for more than a week. These changes lead to reduced tiredness and better safety records.
7. The major breakthrough in the study of sleep was the observation of rapid eye movements (REM), which indicate that a sleeper is dreaming. Measures of physiological processes such as the electroencephalograph (EEG) also aid sleep research.
8. A sleep cycle lasts about 90 minutes and starts with non-REM (NREM) sleep. We descend through NREM Stages 1 to 4 and then ascend through them to rapid eye movement (REM) sleep. In the average adult, this cycle repeats itself about four to six times each night. REM sleep is associated with dreams, a high level of brain activity, and paralysis of the major voluntary muscles.
9. The amount of time spent sleeping varies with age. The average sleep decreases from about 16 hours at birth to about 7 to 8 hours in young adulthood, with little change thereafter. Observations of individuals during multiple sleep latency tests suggest that many people are not getting enough sleep to feel refreshed each day. Sleep efficiency (time in bed actually asleep) is lower among elderly people, who experience less slow-wave sleep and spend increased time in the lighter stages of sleep. Naps are more common than many people believe and tend to have a refreshing effect.
10. Sleep-deprived individuals usually recover quickly from their loss of sleep. While deprived, they experience microsleeps, which can cause poor performance on tasks requiring attention.
11. REM sleep deprivation leads to the REM rebound, an increase in the amount of REM sleep. Infants spend about 50 percent of their sleep in REM, perhaps to provide stimulation needed for brain development. Sleep may have evolved to fill time, but the amount of sleep in each species depends on vulnerability to predators and the need to find food.
12. Most cases of insomnia are of short duration. Sleeping pills have limited usefulness and should be used with care. The stimulus control method is an effective treatment for many cases of sleep onset insomnia.
13. Hypersomnias are sleep disorders that are marked by excessive daytime sleepiness. Narcolepsy is characterized by daytime sleepiness, cataplexy, and other symptoms consistent with the intrusion of REM sleep into waking hours. Overweight middle-aged men are susceptible to sleep apnea, which consists of frequent pauses in breathing during the night.
14. Parasomnias are sleep disturbances other than insomnia and hypersomnias. Sudden infant death syndrome (SIDS) is the leading cause of death for infants between 1 week and 1 year of age. Placing infants to sleep on the side or back may reduce the incidence of SIDS. Enuresis (bedwetting) is a common disorder in childhood and can be treated with the urine alarm. Sleepwalking (somnambulism) and sleep terrors are associated with Stage 4 sleep, tend to occur in children, and usually disappear without treatment. REM sleep behavior disorder occurs in older men and consists of aggressive actions during REM sleep. Nightmares are bad dreams that occur during REM sleep.
15. As typically defined, dreams are associated with REM sleep, although NREM sleep is not a mental void. Freud suggested that dreams serve to fulfill wishes, especially of a sexual or aggressive nature. Analysis of the manifest content of a dream yields the dream's latent content, or true meaning. Waking activities can interfere with the ability to recall dreams.
16. The activation-synthesis hypothesis suggests that dreams result from attempts by the brain to make sense of high levels of neuronal activity. The parts of the brain that are stimulated during REM sleep account for the characteristics of most dreams.
17. Hypnosis can be traced to the eighteenth century, when Franz Anton Mesmer claimed that he had the power to induce magnetic equilibrium in the bodies of his patients.
18. Hypnosis can be defined as a heightened state of suggestibility. Contrary to the view that it is an altered state of consciousness, evidence shows that it does not differ from a state of relaxation.
19. Hypnosis has been used to reduce pain and in various kinds of medical treatments. However, it is not clear what aspect of hypnosis may be responsible for pain reduction; relaxation, distraction, and expectations seem to play significant roles.
20. Hypnosis has been used in improve recall. However, hypnotically refreshed memories tend to contain distortions and false reports. Individuals who have had their memories refreshed through hypnosis are actually more confident in their memories.
21. In hypnotic age regression, a hypnotized person appears to return to childhood or perhaps even to past lives. Research indicates that age regression results in the reporting of fantasies or memories suggested by the hypnotist.
22. There are competing explanations of hypnosis. The cognitive-social explanation suggests that the observed phenomena can be explained by the relationship between the hypnotist and the hypnotized individual, as well as by widely shared expectations about the procedure. Another explanation, offered by Ernest Hilgard, suggests that dissociation may be at work in cases of hypnosis.
23. Psychoactive substances are chemicals that affect consciousness, perception, mood, and behavior. Regular and excessive use of drugs can lead to substance abuse or substance dependence.
24. Alcohol is a widely used psychoactive drug. The use of alcohol is associated with a wide range of medical and psychological consequences including cirrhosis of the liver. Alcohol is a depressant; its major effect is on parts of the brain responsible for inhibiting behavior.
25. The effects of alcohol are related to blood alcohol concentration (BAC), an indication of the amount of alcohol in the blood. Your BAC is determined by how much you drink, the time you take to drink it, your weight, and whether you have consumed food before or while drinking.
26. Expectations about the effects of alcohol can influence drinking patterns. However, the relationship of alcohol to violence seems to be due to its biological effects, not to expectations.
27. The rate of alcohol abuse and dependence is higher in men than in women.
28. Like alcohol, barbiturates are depressants; they slow the activity of the central nervous system.
29. Stimulants such as amphetamines speed up the activity of the nervous system. One of the most widely used stimulants is caffeine, which is found in foods such as chocolate, beverages such as coffee, and some medications. Nicotine, a major component of tobacco smoke, is associated with several preventable diseases such as heart disease. Cocaine can get to the brain quickly and cause a powerful high followed by a dramatic low.
30. Opioids, such as morphine and codeine, are drugs derived from the seedpod of the poppy plant; their primary medical use is to reduce pain. Heroin is a synthetic compound that is derived from morphine.
31. A variety of drugs known as hallucinogens can cause changes in perception, including hallucinations. Among the best-known hallucinogens are lysergic acid diethylamide (LSD) and phencyclidine piperidine (PCP). Marijuana consists of dried leaves and flowers from the Cannabis sativa plant. The active psychoactive ingredient in marijuana is THC.
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