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Human beings spend one third of their life sleeping. Hence it is a behavioral state that is natural for all individuals. Prior to 1950 it was believed that a person’s body and mind is shut up when sleeping. But later intensive scientific research carried out by various scientists proved that various parts of our brain remain active even when we are asleep.

Sleep is an activity not an option. A person deprived of sleep often suffers from lack of concentration, memory loss, fatigue, depression and as a consequence emotional instability. Hence it is important to gather scientific information about changes that occur in the body during sleep and how those changes affect our ability to move and behave rationally.

Why do we fall asleep?
The scientific explanation which gives the reason of sleeping is that through out the day a chemical called adenosine is accumulated in the human beings. It makes people feel more and more tired. Once a person goes to sleep this adenosine breaks down. Moreover, when we go to sleep those nerve cells in the human brain called neurons become active which makes us to go to sleep switching off the neurons that keeps us active.

Misconceptions about sleep
The following are the myths related to sleep and their correct explanation:

1. During sleep body and brain goes to rest – There are some modest decrease in   metabolism rates but not all organs take rest when we go to sleep.

2. Body adjusts to different sleep schedules easily – It is not easy for the biological clock to adjust with your shift schedules. People, who work at night and sleep in daytime, still feel sleepy at night. You cannot make your biological clock work as you wish.

3. People need less sleep as they go old – It is not necessary to sleep less as you go old. It happens mostly because of various diseases that hampers the sleep.

4. Sleeping less at night doesn’t affect daytime functioning – It gives rise to a condition of “sleep debt”. It has a negative effect on daytime functioning and people, who suffer from sleep debt, complain of fatigue, mood swings and depression.

5. Good night’s sleep decreases morning sleepiness – The people who suffer from insomnia or other sleeping disorders complain of morning sleepiness and even excessive sleeping for a day or night cannot cure them of that. They must seek professional help.

Sleep measuring tools

The following instruments are used by scientists to measure sleep in humans.

1. EEGs (electroencephalograms) – This machine is used by the scientists to study electrical changes in the brain through electrodes and the data is represented by graphs as per their frequencies and termed as ‘waves’.

2. EOGs (electrooculograms) – The scientists use electrodes on the skin near the eye to measure changes in voltage as the eye rotates in its socket.

3. EMGs (electromyograms) – The scientists when using this technique, place electrodes on the skin overlaying a muscle.

In practice, EEGs, EOGs, and EMGs are recorded simultaneously on continuously moving chart paper or digitized by a computer and displayed on a high-resolution monitor. This allows the relationships among the three measurements to be seen immediately and the studying these data scientists decipher the sleeping pattern in human beings.

Five stages of sleep

1. First Stage- In this stage eye and muscle movements are slow.

2. Second stage- Eye movements stop, brain activity slows; infrequent rapid bursts of brain activity exist.

3. Third stage- Very slow brain activity, frequent small brain activity bursts. It is difficult to disturb at this deep sleep level.

4. Fourth stage- Only slow brain activity occurs now. No eye or muscle activity. It is difficult to disturb anyone at this deep sleep level. If awaken, it takes a few minutes to orientate one’s self.

5. Final stage REM (rapid eye movement)- Increased breathing, more irregular, shallow breathing, rapid random eye movement. Muscles in limbs become paralyzed temporarily. Heart beats increase per minute and there is gradual increase in blood pressure. Dreaming is frequent and sometimes vivid.

Functions of different organs during sleep cycle:

1. Endocrine system-Sleep determines the hormone secretion in human beings. For e.g. Follicle stimulating hormone (FSH) and luteinizing hormone (LH) in females which are responsible for menstrual and reproductive processes, are among the hormones released during sleep. In fact, the sleep-dependent release of luteinizing hormone is thought to be the event that initiates puberty. Other hormones, such as thyroid-stimulating hormone, are released prior to sleep.

2. Renal System- The kidney functioning, release of chemicals like sodium, potassium, calcium etc., plasma flow etc are reduced during sleep. This is the explanation of urine concentration in large amounts during sleep.

3. Alimentary system– The alimentary system in human beings slows down when a person goes to sleep. Secretion of digestive juices are decreased and reduces the digestion process.

Hence sound sleep is necessary for proper functioning of the body. Usually hours of sleep that is required varies from person to person but an adult human being need at least of 8 hours of sleep on a daily basis for normal functioning. Teenagers are recommended 9-10 hours of sleep.