WHAT IF YOU NEVER FELT THIRST?

Throughout the day, there are systems that detect the slightest changes to the amount of water in your body. The main one is an area, about the size of an almond, in the brain called the hypothalamus. Among other things, the hypothalamus is sensitive to the water content of the blood. When the water level drops, there is a noticeable, albeit small, decrease in blood pressure. At this point, baroreceptors come into play. Located at the aorta, where blood first exits the heart, they are involved with detecting changes in blood pressure. On being activated, these sensitive receptors immediately send a message to the hypothalamus, which in turn responds by ordering the pituitary, the pea-sized gland right beneath it, to begin producing and secreting a hormone called vasopressin, or ADH.

Via the bloodstream, this hormone embarks on a long journey and eventually arrives at the kidneys. Just as a key fits into its intended lock, the kidney has special receptors that are just right for this hormone. When it reaches the receptors, they communicate the message that the kidneys need to go into water-saving mode, and the kidney cells immediately begin retaining water, to bring the amount of water lost to a minimum.

This same hormone also causes the sensation of thirst in the brain. And as a result of this perfect built-in system, of which we are totally unaware, we can balance our body's water level with a glass from the faucet.

Adrenal glands produce hormones that activate the region of thirst in the brain. Information obtained from the baroreceptors in the heart is taken to the hypothalamus. Once enough water has been taken in, the message is sent from the tongue and stomach that reserves are now full. The hypothalamus commands the salivary glands to stop production, and as a result, the mouth goes dry.

If there were no pituitary hormone, or if kidney cells weren't able to understand and obey its command to retain water, we would need to drink between 15 and 20 liters of water a day in order not to die of thirst. And because we'd need to void this water continually, we wouldn't be able to sleep or stay in one spot for any length of time.

As we've seen, all parts of the system that balances our body's water level cooperate with the brain. Cells in the aorta notify the brain of the lack of water. Immediately realizing the consequences of this message, the brain then releases a signal that goes to the kidneys, the relevant organs out of all the others in the body, and tells them what to do.

These processes take place in our bodies countless times during the day, without our even being aware of them. Moreover, they take place in the bodies of all the people around us, and in all the people who have ever lived and will live in future. They all possess the same sensitive receptors. All their cells know how to respond to changes in blood pressure. The cells of every human being have been given this ability to measure changes in blood pressure.

How did such a complex and faultless system come about, appearing with the identical qualities in every single person?

That such a mechanism couldn't arise as a result of blind coincidence is clear to every person of intelligence. Also, it's not possible for this system's parts to have acquired these features on their own. Cells themselves cannot discover processes that even a human requires careful attention to read and understand. Moreover, vasopressin is only one of the hundreds of hormones found in the body. Each of the others has a similar relationship to its appropriate organ. And no hormone ever takes its message to the wrong place; every organ understands correctly and fully the message that the hormone carries.  It's patently obvious that such a system was brought into existence by a superior Intelligence. The possessor of this intelligence is God, the Creator of everything.

Every human is responsible for reflecting upon these miracles of creation in their own bodies and for expressing gratitude to God, Who created them in such perfection.

God makes the signs clear to you and God is All-Knowing, All-Wise.
(Qur'an, 24: 18)