Sleep Deprivation

• People typically go through about four sleep cycles during one night of sleep. The REM stage of sleep gets longer and longer as the night passes, while stage 3 and 4 sleep gets shorter and shorter. During the night’s first sleep cycle, the REM stage lasts about ten minutes. During the night’...

• When people are relaxed and ready to fall asleep, their EEG will show mostly alpha waves. When people fall asleep, they enter into stage 1 sleep, which lasts just a few minutes. In stage 1, the EEG shows mostly theta waves. Heart rate, breathing rate, and body temperature drop, and muscles r...

Biological rhythms usually synchronize with environmental events such as changes in daylight. However, experiments have shown that many biological rhythms continue to have the same cycle even without cues from the environment. Such biological rhythms are Endogenous, which means that they originat...

• People then pass into slow-wave sleep, which occurs during stages 3 and 4. In stages 3 and 4, which together last about thirty minutes, the EEG displays mostly delta waves. People in stage 3 and 4 sleep show slow breathing and pulse rates, have limp muscles, and are difficult to rouse.

• At the end of stage 4, people go back through the stages in reverse, from stage 4 to 3 to 2 to 1. When they reach stage 1, instead of waking up, people go into REM, or rapid eye movement, sleep. A single cycle might look like this: ' 123432REM '
• REM sleep is a stage of deep sleep in ...

• Everyone has occasional difficulty sleeping, but some people have Insomnia, a chronic problem with falling or staying asleep. Another kind of sleep disorder is Narcolepsy, which is a tendency to fall asleep periodically during the day. Narcolepsy can be dangerous, as people who experience it...

Sleep is just one of many types of consciousness we experience, and sleep itself comprises several states of consciousness. Even when we’re sleeping, our brains and bodies continue to work.

Sleep is affected by biological rhythms or periodic physiological changes. Biological rhythms are reg...

Most people in stage 4 sleep are still, quiet, and difficult to rouse. Sleepwalkers, however, sometimes become physically active during stage 4. They may get up and walk around their room or even carry on a conversation, take a bath, cook, or go outside and get in their car. Because they are in a...

• Sleep apnea is another condition that can have negative effects on health and safety. People who have Sleep Apnea stop breathing many times during a night’s sleep, and each time they stop breathing, they wake up briefly and gasp for air. This prevents them from getting enough deep sleep, whi...

• During REM sleep, pulse rate and breathing become irregular, eyes move rapidly under closed lids, and muscles remain very relaxed. Genital arousal also happens during REM. In women, the clitoris becomes swollen with blood, and vaginal lubrication increases. In men, the penis becomes erect. E...

Although everyone sleeps, no one really knows why people sleep. Researchers have proposed several theories to explain how sleep evolved to be a necessary behavior:

1. People conserve energy by sleeping periodically.
2. Sleep has a protective function, as it keeps people tucked away a...

1. Circadian Rhythms: biological cycles that occur about every twenty-four hours. Sleep follows a circadian rhythm. Hormone secretion, blood pressure, body temperature, and urine production also have circadian rhythms.
2. Infradian Rhythms: biological cycles that take longer than twenty-fo...

Endogenous rhythms exist because the body has biological clocks that keep time. Biological clocks can be adjusted by environmental cues, such as changes in temperature.

In humans, the Suprachiasmatic Nucleus (SCN) is the main biological clock that regulates circadian rhythms of sleep. The S...

Jet lag is the fatigue and disorientation air travelers feel after a long flight. Although traveling itself drains energy, the time change also contributes to fatigue. People experience jet lag when the events in their environment are out of sync with their biological clocks.

EXAMPLE: A tra...

Sleep research has provided a lot of information about what happens to the brain and body during sleep. Researchers study sleep by monitoring subjects who spend the night in labs, and they use various instruments for different purposes:

1. Electroencephalographs(EEGs): record brain waves

During one night’s sleep, people pass through several cycles of sleep, each lasting about ninety to one hundred minutes. There are five distinct stages of sleep in each cycle: 1, 2, 3, 4, and REM.