Levels of Sleep CyclesTop Topics

5 Things Your Body Expects You to Know About Levels of Sleep Cycles

A lot happens in your body while you sleep, as you cycle between REM and Non-REM sleep. REM stands for “rapid eye movement”, during which your eyes move quickly in different directions. That doesn’t happen during non-REM sleep.

Sleep was once considered an inactive, or passive, state in which both the body and the brain “turned off” to rest and recover from the day’s activities.

Scientists have since found that the brain goes through characteristic patterns of activities throughout each period of sleep, that it is sometimes, even more, active than when we’re awake.

Understanding these patterns of sleep, and the factors that affect them may help in making choices that will lead to better quality sleep.

The Nature of Sleep

Prior to the era of modern sleep research, scientists regarded sleep as an inactive brain state. It was generally accepted that as night fell and sensory inputs from the environment diminished, so do brain function too.

As a result of that, scientists thought that the brain simply shut down during sleep, only to restart again when morning came.

An invention In 1929 enabled scientists to record brain activity,  and from recordings known as electroencephalograms (EEGs), researchers could see that sleep was a dynamic behavior, one in which the brain was highly active at times, and not turned off as previously thought.

Over time, sleep studies using EEGs and other instruments that measured eye movements and muscle activity would reveal there are two main types of sleep. These two were defined by characteristic electrical patterns in a sleeping person’s brain, as well as the presence or absence of eye movements.

The two main types of sleep are “rapid-eye-movement” (REM) sleep and “non-rapid-eye-movement” (NREM) sleep. On an EEG, REM sleep, often called “active sleep,” is characterized by low-amplitude (small), high-frequency (fast) waves and alpha rhythm, as well as the eye movements.

Many sleep experts think that these eye movements are in some way related to dreams, because, when people are awakened from REM sleep, they usually report that they had been dreaming, often extremely vivid dreams.

In disparity, people report dreaming far less frequently when awakened from NREM sleep. It is interesting to know that, during REM sleep muscles in the arms and legs are temporarily paralyzed, and experts believe it to be a neurological barrier that prevents us from “acting out” our dreams.

NREM sleep can be broken down into distinct stages.

The 4 Stages of Sleep and Why They Matter

During sleep, our brain cells work more slowly but more intensively, and this shows up on an EEG as an electrical activity that is lower in frequency but higher in voltage.

When we sleep, there are also physical changes in the body such as changes in eye movement and muscular tension. Further changes in electrical activity in the brain show when each stage of sleep begins and ends.

Sleep Stage 1

In this stage, our breathing and heartbeat become regular, our muscles relax and our body temperature falls. We become less aware of external stimuli and our perception of reality starts to withdraw.

The slightest noise is enough to wake you from this stage. You must have experienced the sensation of falling suddenly, typical of this stage. We spend about 10% of the night either awake or in stage 1, which generally lasts between 13 and 17 minutes.

Some people twitch during this stage, which, in effect, is the stage during which we fall asleep. As such, it occurs only once during a night of uninterrupted sleep.

Sleep Stage 2

Sleep becomes deeper during stage 2, and our muscles relax further. Physical sensations are significantly reduced and our eyes do not move. About half of our total sleeping time is spent in stage 2, and at this stage, electrical activity in the brain occurs at a lower frequency than when we are awake. Both stages 1 and 2 are known as the light-sleep phase, and they last for about 20–30 minutes together. We usually fall back to stage 2 several times during the night.

Sleep Stages 3

At stage 3, we reach the first of our deep-sleep stages. This occurs after approximately 20 to 30 minutes when our body is now completely relaxed, and we are more or less completely disconnected from reality. To wake someone from this deep stage of sleep, you will need to make quite a lot of noise or shake them quite hard.

Sleep Stage 4

Waking someone from stage 4 is a bit like trying to wake a hibernating animal. This is the most restful part of the night’s sleep, where muscular activity decreases even further and our eyes do not move.

Stages 3 and 4 constitute about 20 percent of our time asleep and are known as the deep-sleep phase.

It is during these deep stages of NREM sleep, that the body repairs and re-grows tissues, builds bone and muscle, and strengthens the immune system.

As you get older, however, you sleep more lightly and get less of these deep sleep stages. Aging is also linked to shorter time spans of sleep, but you will still need as much sleep as when you were younger.




The Sequence of Sleep Stages

Our sleep follows a specific sequence. It appears we complete a sleep cycle and begin a new one approximately every 80 to 110 minutes (usually around 90 minutes).

A night’s sleep begins with a light-sleep phase of varying length, followed by the first deep-sleep phase of the night and a short REM phase. In the second half of the night, we spend a relatively shorter amount of time in deep-sleep phases and our REM phases tend to be longer. The final REM phase of the night may last for as long as 30 minutes or more, and then, we wake up.

During the first year of life, children spend most of their time asleep in REM sleep, but from the age of four, the proportion of REM sleep falls to about 20% of the night sleep.

People over the age of 60 spend only about 15% of the night sleep in REM sleep, and the pattern of REM sleep changes as we grow older.

With the exception of infants, people spend most of the night in the light-sleep phase, and if the amount of time we sleep is reduced, it’s the light sleep phase that suffers the deficit. This ensures that we still make it to the deep-sleep phases, which have the most restful effect.

Nevertheless, we need to spend some time in the light-sleep phase in order to reach the deeper sleep phases, as it is not possible to access deep sleep immediately after falling asleep. Good sleep takes time to build.

Each sleep phase serves a specific purpose for the body, and the primary function of both light and deep-sleep phases is to have a regenerative effect on various processes in the body.

During the REM phase, the brain is almost as active as when we are awake, and we need both deep sleep and REM sleep to properly process the impressions and memories of the day.

Sleep Cycle Changes And Your Health

A new study suggests that when routine sleep habits are disrupted, that increases your risk for diabetes and heart disease.

The study found that those with large differences in their sleep schedules on workdays and free days tended to have worse cholesterol and fasting insulin levels, greater insulin resistance, larger waist size, and higher body mass index (BMI). The body mass index, BMI is an estimate of body fat based on height and weight.

The most basic daily rhythm we live by is the sleep-wake cycle, which is related to the cycle of the sun. It makes us feel sleepy as evening draws near and wakeful as the day sets in.

Sleep-wake and other daily patterns are part of our circadian rhythms, which are governed by the body’s internal or biological clock, found deep within the brain.

Research has been finding that the body’s clock is responsible for more than just sleep and wakefulness, as other systems, like hunger, mental alertness, and mood, stress, heart function, and immunity also operate on a daily pace.

Jet lag and shift work can throw our normal patterns out of whack and take a toll on our physical and mental health. Even shifting the clock an hour forward or backward when daylight savings time begins or ends can disrupt some people’s biological clocks.

There is the problem that a night-time schedule places you at greater risk of heart disease, diabetes, gastrointestinal illnesses and reproductive problem. For people whose body clocks are misaligned for many years, there is also the risk or higher rates of developing some cancers.

Unfortunately, nobody knows really why disrupting the dark-light sleep-wake cycle should have such an impact on our health. Though researchers are unpacking the problem little by little, there are still a lot of assumptions about circadian rhythms and body clocks and who knows what.

The idea of a biological clock may sound like a quaint metaphor, but there is actually a very distinct brain region that is charged with keeping time; an area called the suprachiasmatic nucleus (or SCN), situated right above the point in the brain where the optic nerve fibers cross.

This location enables the SCN to receive the cues it needs from light in the environment to help it maintain time.

Genes may influence the body’s clock and circadian rhythms since the system requires both types of input light and genes to keep it on track.

To stay on the 24-hour cycle, the brain needs the input of sunlight through the eyes to reset each day, and when humans are allowed to run off their body’s clock apart from input from the sun (by being kept in continuous darkness), the body’s daily cycle tends to lengthen to about 25 hours.

Also, when people lack the genes that help control the clock’s cycle, their sleep-wake cycles can stray even further, or be absent completely. The need for both light and genes, make the biological clock a good example of how genes and the environment work in harmony to keep the system functioning well.

 

How to Sleep Better Naturally

The benefits of adequate sleep are numerous as it ranges from better heart health and less stress to improved memory and weight loss.

Keep In Sync With Your Body’s Natural Sleep-Wake Cycle

Synchronizing with your body’s natural sleep-wake cycle, or circadian rhythm is one of the most important strategies for sleeping better. If you maintain a regular sleep-wake schedule, you’ll feel much more refreshed and energized than if you sleep the same number of hours at different times, no matter how little, the alteration is.

Try to go to sleep and get up at the same time every day, as this helps set your body’s internal clock and optimize the quality of your sleep. Choose a bedtime when you normally exhausted, so that you don’t toss and turn. If you’re getting enough sleep, you should naturally wake up without an alarm.

Avoid Sleeping in-even on Weekends.

The more your weekend or weekdays sleep schedules differ, the worse the jetlag-like symptoms you’ll experience. If you need to make up for a late night, opt for a daytime nap rather than sleeping in on weekends. This allows you to pay off your sleep debt without disturbing your natural sleep-wake cycle.

Sleeping until noon on Saturday will only disrupt your biological clock and cause more sleep problems. Going to bed at the same time every night even on weekends, holidays, and other days helps to establish your internal sleep/wake clock and reduces the amount of effort (if any) required to fall asleep.

Change Your Diet

Cut out the food and drinks that contain caffeine, such as coffee, chocolate, etc by mid-afternoon, and make dinner your lightest meal. Finish dinner a few hours before bedtime, and skip spicy or heavy foods, which can keep you awake with heartburn or indigestion.

Don’t Smoke

A study found that smokers are four times more likely not to feel well rested after a full night’s sleep than non-smokers. The Researchers attribute this to the stimulation or effect of nicotine and the nighttime withdrawal from it. Smoking also exacerbates sleep apnea and other breathing disorders such as asthma, which can make it difficult to get a good restful sleep.

Exercise During The Day

People, who exercise regularly during the day, sleep better at night and feel less sleepy during the day. Regular exercise also improves the symptoms of insomnia and sleep apnea and increases the amount of time one spends in the deep, restorative stages of sleep.

The more vigorously you exercise, the more powerful the sleep benefits, but even light exercise, such as walking or jogging for few minutes, improve sleep quality.

It can take sometimes of regular exercise activity before you experience the full sleep-promoting effects. Be patient and focus on building an exercise habit.

Exercise speeds up your metabolism, elevates body temperature, and stimulates hormones such as cortisol. So, try to finish moderate to vigorous workouts at least three hours before bedtime. Relaxing, low-impact exercises such as yoga or gentle stretching in the evening can also help promote sleep.

Relaxation Techniques For Better Sleep

Practicing relaxation techniques before bed is a great way to wind down, calm the mind, and retire to good sleep. Deep breathing, where you make each breath even deeper than the last, is a good start.

Progressive muscle relaxation, where you start with your toes, tense all the muscles as tightly as you can, then completely relax, before working your way up to the top of your head is another relaxation technique for better sleep.

Visualizing a peaceful, restful place that’s calming and peaceful can help you do the trick. Concentrate on how relaxed this place makes you feel, and you may be off to a good night rest before you know it.

 

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