We all have at least a vague notion of what sleep is, the definition of sleep in dictionary says that is a condition of body and mind which typically recurs for several hours every night, in wich the nervous system is inactive, the eyes closed, the postural muscles relaxes, and counsciousness pratically suspended. But is so much more than that.
It's difficult to do a detailed analysis of our own sleep given that we rarely know that we're sleeping when we're asleep. And even when we observe the sleep of others, so much of what they experience is not easily seen from the outside.
There was a time when people thought that sleep was simply a time when the body and brain "shut off" for a few hours each night to rest in preparation for the next day. But now scientists understand that neither the body nor the brain "shut down" when we sleep, in fact, they are often working harder than they do during the day, undergoing processes to restore cells, process information, and improve health.
The human body follows a natural 24-hour pattern, approximately, called the circadian rhythm. This rhythm is influenced by the environment (such as lightness) as well as your genetic makeup and determines your sleep patterns by releasing hormones when it's time to sleep. Abnormalities in the circadian rhythm can lead to sleep disorders like insomnia.
Sleep has two main phases - REM and non-REM. We spend about a quarter of our sleeping lives in the REM phase, which is a period of vigorous brain activity, marked by vivid dreams. This stage may be responsible for consolidating information and processing memories, which is why babies spend twice as much time in REM sleep than adults do, since those days are full of new experiences that brain needs to process.
Non-REM sleep has three to four distinct stages. These grow gradually deeper throughout the night until it becomes very difficult to be disturbed from sleep. During this time, the body works to gently lower the heart rate, temperature and breathing rate.
You can know more of Stages of Sleep in here.
Everyone
needs sleep, but its biological purpose remains a mystery. Sleep affects almost every type of tissue and
system in the body – from the brain, heart, and lungs to metabolism, immune
function, mood, and disease resistance.
Research shows that a chronic lack of sleep, or getting poor quality
sleep, increases the risk of disorders including high blood pressure,
cardiovascular disease, diabetes, depression, and obesity.
Sleep is a complex and dynamic process that affects
how you function in ways scientists are now beginning to understand. Based on research and monitoring the brains of sleeping people, they have some ideas of how sleep is important:
- Offers the body a chance to recover from daily life. Many researchers have suggested the restorative effects of sleeping. This doesn't just mean that the body rests during sleep, rather, the cells busily regenerate themselves and the body temperature, heart rate and breathing drop in order to conserve energy.
- Facilitates learning and memory.
- Plays a role in imune function.
Your body produces special proteins called cytokines, which help your imune system fight off infection. According to the U.S. Department of Health and Human Services, more of these proteins are produced during sleep when you are sick, which is one of the reasons you may feel so tired when you have the flu. Rest gives the body the time it needs to produce these infection-fighting proteins and to restore itself to wellness.
Not only do you need rest to sustain the attention and cocnentration necessary to learn new tasks, but according to Harvard's Division of Sleep Medicine, sleep is a time for the brain to consolidate memories, which makes learning new things easier. People who sleep after learning how to play a video game generally perform much better in the game later than those who stay awake. Even more intriguingly, a recent study in Natural Neuroscience showed that people can even learn completely new behaviours (in this case, to associate unpleasant and pleasant odors with certain sounds) while they are completely asleep.
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