The body systems required some rest, and average sleeping would help in this regard.

The body systems required some rest, and average sleeping would help in this regard.

Thanks for the recommendation

Anyone needs to be relaxed to be well prepared for the daily work.

We should not devote much time for sleeping, it makes us lethargic. 5 to 6 hours in a day is okay for healthy work flow of our routine.

Dear Prof Urooj, Osama and Munaf,

Many thanks!, for your answer to my question.

Dear Ajay Kumar , it is an interesting question. I have some sleeping problem this days and the need of investing more time has came to me very clearly.

A number of proposals and perspectives have emerged that, taken together, paint a compelling and converging picture for why sleep evolved and why it is now needed.

Why sleep evolved

Collectively, these four environmental and biological pressures lead to a bifurcation of external interactive behavior and internal maintenance activity that is synchronized with the 24-hour day/night cycle. They further encourage all postponed internal maintenance activities to be synchronized and performed in parallel, in other words, sleep.

Given the different day vs. night ecosystems, it is natural that animals that have a survival edge during one phase of the 24 hour cycle would use the other phase for sleeping. "Diurnal" animals are specialized for engaging with the daytime environment, whereas "nocturnal" animals (cats, kangaroos, owls) are specialized for night and sleep during the day. However there are other patterns as well, such as "crepuscular" animals that are active at the day/night boundary (dawn, dusk).

Why sleep is now needed

Given that a regular sleep period has formed, the question is: What goes on during sleep that is so important?

There appears to be no one single sleep activity that is the reason for sleep. Because the sleep/wake division of the 24-hour activity cycle has been around in animals for a long time -- all known animals have a quiescent period -- the sleep period has had hundreds of millions of years to acquire multiple uses.

At the cellular level, removing toxic radicals and strengthening or rebuilding tissues has been suggested.

In the brain, a number of uses for sleep have been identified or proposed [1], including:

"At the whole animal behavioural level, the functions of sleep seem clear: energy is saved, performance is restored and (in humans) affect becomes more positive. Such findings have led to the universal acknowledgement that sleep restores brain function." [1]

Sleep as a Diverse and Decentralized Phenomenon

A wide variety in sleep patterns can be found across animal species. Some animals (insects, fish) are quiescent but not fully "asleep" (inactive). In cetaceans (whales and dolphins), half of the brain goes to sleep at a time for 1-2 hours on an irregular schedule throughout the day and night. Bears, bats, and some rodents hibernate, which is a quiescent extended-sleep period lasting for weeks or months in the winter. Siegel (2008) reviews the phenomenon of sleep across animal species. [2]

Krueger et al (2008) reviews the functions and mechanisms of sleep in the brain and proposes that sleep is not a centralized process of the brain, as is normally thought, but is instead a decentralized intrinsic process of neural tissue. They propose that neural tissue initiates sleep onset in a decentralized fashion that propagates until it takes over the whole brain, in something like a social mass movement. The evolutionary pressure to partition activity into day/night divisions is also discussed.

A good way to understand the role of sleep is to look at what would happen if we didn't sleep. Lack of sleep has serious effects on our brain's ability to function. If you've ever pulled an all-nighter, you'll be familiar with the following after-effects: grumpiness, grogginess, irritability and forgetfulness. After just one night without sleep, concentration becomes more difficult and attention span shortens considerably. With continued lack of sufficient sleep, the part of the brain that controls language, memory, planning and sense of time is severely affected, practically shutting down. In fact, 17 hours of sustained wakefulness leads to a decrease in performance equivalent to a blood alcohol level of 0.05% (two glasses of wine). This is the legal drink driving limit in the UK.

Source BBC;

About 5 to 6 hours of sleep per day is essential to keep ourselves fresh and fit. Basically sleeping is our basic needs. If we will not sleep then a numbers of complications start. So many people have bad immune system, and many are suffering from tension, depression and anxiety. In my opinion a normal healthy person must have a sound sleep of about 6 hours per day.

If we can't well sleep, there may be the nervous and consequent health problems.

However, in some mission or flight trips for far countries, we have not enough sleeping time.

Sometimes, during the important task working, I can't sleep in some nights.