Among His signs is sleep

In the Name of Allah, The Most Gracious, Most Merciful
Scientists hold that sleep is the greatest of all of Allah’s Divine Favors upon mankind. This is because it revives the human body and renews its energy. In this context, Allah, All-Mighty, says,

“And among His (Allah’s) Signs is your sleep by night; and by day, your seeking of His Bounty. Verily, in that are indeed Signs for a people who listen.” [XXX; 23]

The most up-to-date studies in the field of sleep confirm that when man gets up and starts work, certain chemicals are produced in small amounts in his body. By time and labor, the amounts of these chemicals increase until they reach a certain ratio in the blood. Therefore, messages are sent to the brain, which, in turn, sends neuro-electric orders to the sleep-centers in the nerve-endings. The nerve-endings either dissemble and cut off the neuro-electric current – which causes man to sleep – or assemble together, allowing the neuro-electric current to pass along – which keeps man awake. Hence, mechanism of sleep is made up of a chemical substance, or a compound of substances, that are produced increasingly in the human body by time and labor, until messages are sent to the brain, which, in turn, sends neuro-electric orders to the sleep-centers in the nerve-endings, which dissemble, cutting off the neuro-electric current and causing man to feel exhausted and to fall asleep.

Now, the question is:
Whose arrangement is this?! Whose organization is this?! Whose creation is this?! How would our life be without sleep?! If man stays awake for two straight nights, he will certainly get confused and exhausted. So, what would happen to man if he were deprived of sleep?! Once again, we repeat Allah’s Divine Words,

“And among His (Allah’s) Signs is your sleep by night; and by day, your seeking of His Bounty. Verily, in that are indeed Signs for a people who listen.”

In the human body there are centers for light sleep and centers for heavy sleep. In other words, you might stay in bed for eight hours. during one or two of these eight hours, you are heavily asleep and completely unconscious of anything around you. But during the rest of these eight hours, you are lightly asleep and conscious of all the things taking place around you:
you are conscious of those who speak, come in, get out, or knock on the door.
The question is:
Who has made in the body centers for light sleep, sh3er for heavy sleep, and sh3er for remaining awake?!
A baby usually sleeps for long hours in order that its body grows. A five-year old child sleeps for 12 hours, an adolescent for 9 hours, and an adult for 7-8 hours.
The question is:
Who has planned sleep?! Who has set its periods and times?! Who has made it time for rest and comfort for muscles and organs of the body?! Once again, we reiterate Allah’s Words,

“And among His (Allah’s) Signs is your sleep by night; and by day, your seeking of His Bounty. Verily, in that are indeed Signs for a people who listen.”
Praise be to Allah, the Lord of Creations