The desire to drink water is called Thirst. Thirst occurs for two reasons:

1. Decreased volume of intermolecular fluid
2. Increased osmolarity in plasma

Our Body is made up of countless cells. Cells are connected to each other but there is space between them. This space is called extracellular space. Intermolecular space is a special type of liquid. There is a feeling of thirst when the volume of this liquid decreases.

The cells of our body are surrounded by a thin membrane. This membrane is semipermeable. If there is a semi-permeable membrane barrier between the two solutions, the solvent travels from the low-concentration solution to the high-concentration solution, until the concentration of the two solutions is equal. This process is called osmosis. In this process the semi-permeable membrane allows only the molecules of the solution to pass through, the molecules of the solute cannot pass through it hence it is called a semi-permeable membrane. For example, if a semi-permeable membrane has a sugar solution on one side and water on the other, the water molecules will move toward the sugar solution.

The fluids in our body are called plasma, such as lymph and blood. Plasma contains proteins and inorganic salts. The ratio of substances in plasma is called osmolarity. As the Amount of water in the plasma decreases, the concentration of proteins and salts increases. This phenomenon is called hypertonic osmolarity. When the osmolarity of the cells becomes hypertonic, there is a feeling of thirst and the person normalizes the osmolarity of the plasma by drinking water or other beverages.

Thirst meter?

Drinking water does not immediately become part of our body. It takes time to absorb and normalize osmolarity. But the strange thing is that as soon as we take a certain amount of water down our throats, we feel thirst quenched and we stop drinking water. This phenomenon can be understood with more clarity in the process of drinking camel water. A thirsty camel quickly drinks a large amount of water and suddenly stops drinking. What is the reason for this unique behavior of humans and animals? Scientists believe that there is a mysterious "meter" somewhere in the throat area of ​​the esophagus that controls the required amount of water. The existence and performance of this "meter" is still a mystery. There is a significant difference in the behavior of humans and animals in the process of drinking water when thirsty. The meter that controls the required amount of water in animals works more prominently, while the function of this "meter" is not very clear in humans under the guise of social life.

Water balance in the body

Water is delivered to the body in two ways:

1. Water production is a result of carbohydrate metabolism.
2. Drinking water or other beverages.

There are several places for dehydration:

1. Skin
2. lungs
3. Esophagus
4. Kidneys

Under normal physical conditions, almost as much water is excreted as is injected into the body and a certain amount of water remains constant in the body. About 65% of our body is made up of water. Children have 75% water content.

Two types of systems maintain the amount of water in the body:

1. Pituitary intake of water. This mechanism makes you feel thirsty.
2. Discharge of water from the body in the form of excretion of urine. This system also makes you feel thirsty.

Other control mechanisms also contribute to this process, such as the energy-controlling carbohydrate transfer mechanism and the sweat-releasing mechanism that controls body heat.

The mechanism of thirst

The mechanism of thirst is very important. It is the process of drinking water that eliminates dehydration in the body. The process of drinking water in humans is more in control by habits and social requirements than the thirst mechanism. Man often drinks or is forced to drink unnecessary water, tea, coffee, and other beverages. But no animal can be forced to water. There is a famous saying: "You can take a horse to the water but you cannot force it to drink water".

The hypothalamus in the back of the brain controls many of our functions. The hormones released by it control hunger, thirst, sleep, breathing, etc. The pituitary gland also works under the influence of the hypothalamus. Damage to the hypothalamus affects the feeling of thirst.

To understand the system of thirst, scientists conducted experiments on different animals, which are summarized as follows:

The increased osmolarity of body fluids, decrease in intramolecular fluid volume, anemia due to injury or wound or surgery, dehydration due to vomiting and diarrhea, stimulation of osmoreceptors in the hypothalamus Gives a feeling of thirst. The hypothalamus is located near the area where the sensation of thirst is aroused, which produces compounds called ADH. This ADH (Antidiuretic Hormone) is called vasopressin. It stimulates the feeling of thirst. The kidneys also produce another vasopressin known as angiotensin. This stimulant also stimulates the hypothalamus to arouse the feeling of thirst.

If the hypothalamus is injured when the brain is injured, the patient loses the feeling of thirst. Similarly, congenitally mentally ill people do not feel thirsty. They have to be watered from time to time otherwise dehydration occurs in the body. If dehydration is not treated in time, the patient may die. Patients with diarrhea also become dehydrated. In all these cases the dehydration is immediately met by intravenous injection.

Thirst is reduced to 0.5% of the total water in the body. Excess deficiency affects the function of the salivary glands in the throat and produces a small amount of saliva which causes dryness of the throat, palate, and tongue. Excessive sweating, high fever, diarrhea, and excessive consumption of alcohol lead to immediate dehydration. If this reduction is 15 to 20% of the bodyweight then the patient dies.

Moderation is essential

Too much of everything is harmful. Excessive use of water is called hyper hydration. It is also called "water poisoning". But this is rarely seen, for example, when a person drinks a large amount of water in a very short period or for many days. Excessive amounts of water impair the ratio of water to salts in the body. As a result of osmosis, the concentration of salts in the cells is greatly reduced and they are unable to perform their functions. The formation of ADH is also affected due to which the kidneys cannot function properly. Swelling of the brain, fit, coma ... even death can occur due to "water poisoning".

Which water to drink?

Distilled water, although pure, is not suitable for quenching thirst. Its use can also cause water poisoning because it does not contain the salts needed for good health. In contrast, tap water or mineral water is healthier.

Moment of thought

Thirst is a "verse" of God that makes us recognize it. Thirst is a great reward of Gog Almighty which saves us from dehydration. But if this thirst exceeds a certain limit, it also takes the form of torment.