“Sleep that knits up the ravell’d sleeve of care, the death of each day’s life, sore labour’s bath, balm of hurt minds, great nature’s second course, chief nourisher in life’s feast.”
-Macbeth, Act II, Sc. ii
As usual, Shakespeare had it right.
Ernest Hemingway also was on the right track when he said, “I love sleep. My life has a tendency to fall apart when I am awake.”
Modern research has added greatly to our understanding of sleep since the days of Hemingway. We now know much more about what sleep is, and how it helps us.
What happens during sleep?
The brain is quite active when we are asleep. Sleep is not just an opportunity for the brain to shut down. A lot of very important functions are performed by our brains while we sleep. Without this, we would not remain healthy for long.
How do we fall asleep?
A lot of research is going on in this area.
There is a school of thought that says that a chemical called adenosine builds up in our bodies during the day. Once it reaches a certain level, we start feeling drowsy, and eventually fall asleep.
The cells in the brain also produce chemicals. Some of these, such as serotonin and norepinephrine, keep us awake. It is felt that these signals for wakefulness are switched off by cells at the base of our brains at night, allowing us to sleep.
Another chemical which regulates sleep is a hormone called melatonin. This is produced by the pineal gland in our bodies. Its levels are reduced by bright light. At night, the levels of melatonin in our blood rise, and we drift off toward sleep.
How much sleep do we need?
Most adults need between 7-8 hours of sleep. Children and adolescents need more. After adulthood, sleep requirements do not change. Even elderly people need 7-8 hours of sleep.
What are the types of sleep?
Sleep is basically of two types: REM, or rapid eye movement sleep, and non-REM sleep.
Non-REM sleep has 4 stages, I-IV. Stage I is light sleep and Stages III & IV are deep sleep. In the first stage, our eyes move slowly and the activity of our muscles slows down. In the second stage, the eyes stop moving, and brain waves slow down. In the third stage, very slow brain waves are produced, called delta waves. Stage four is a deeper sleep than stage three.
REM sleep is characterized by a rise in heart rate and blood pressure, and, of course, rapid eye movements. The muscles of the arms and legs are temporarily paralyzed (presumably so people do not act out their dreams) and breathing is shallow, fast and irregular. This is the time when intense dreams occur.
Benefits of sleep
- Memory
Research done at the New York University School of Medicine and Peking University Shenzhen Graduate School has shown that the sleeping brain creates more connections between nerve cells, leading to memory formation. This happens during deep or slow-wave sleep, when the brain replays activity from earlier in the day.
So if a student wants to retain stuff for a long time, he or she would be better off studying and then getting a good night’s sleep. This improves learning.
- Housekeeping/Cleaning
Waste materials and toxins build up in the brain in the waking state. The brain has a cleaning system to flush this out: the glymphatic system. This system is ten times more active during sleep, according to recent studies.
- Problem solving
New, creative ways to solve problems are promoted by Rapid Eye Movement (REM) sleep, according to a study by the University of California, San Diego School of Medicine researchers. They believe that there are changes in chemicals produced in the brain during REM sleep, which stimulate the formation of “associative networks.” This apparently allows the brain to take ideas not related to each other, and try to make new connections between them.
- Reflexes and focus
Adequate sleep improves your reaction time and reflexes. This is particularly important when you are driving, since slow reactions can lead to an accident.
People who have slept well are also able to focus better on the task at hand.
- Growth
The body releases more growth hormone during deep sleep (both REM and non-REM). This hormone obviously affects growth in children. It also contributes to muscle mass and cellular repair in children as well as adults.
- Sex hormones
Sleep has an effect on the release of sex hormones, which are important for puberty and fertility.
- Mood
Lack of sleep affects your mood and inter-personal reactions. It increases the risk of developing depression.
- Immunity and infections
Certain proteins called cytokines help the body’s immune system to fight infections. The body makes more of these proteins during sleep.
Studies also show that vaccinations against influenza (and possibly other illnesses) work better to protect people who are well-rested.
- Appetite and weight
Sleep strongly affects how the body uses energy. Production of leptin (a hormone which suppresses appetite) increases during sleep. Simultaneously, the production of ghrelin (a hormones which increases appetite) goes down.
These changes affect body weight, and sleep-deprived people are at risk of obesity.
In fact, there is some data showing that otherwise healthy people who are sleep deprived can show signs of a diabetic-like condition.
- Heart disease
Lack of sleep can also increase the risk of cardiovascular diseases.
Conclusion
Sleep affects almost every tissue in the body.
Make sure you get enough.
Great article with useful information
Great article. Is it true that if you are not getting enough sleep during the weekdays you can “catch up ” over the weekend ?
Not really. A sleep deficit is very difficult to pay off.
Very Informative, specially for young adults !!!! Do power naps count as a replacement for good sleep ???
Yes, if you can reach the stages of deep sleep.