Most of the people think that parching of mouth or throat is only caused by thirst. But, this is not a fact. Such parching can occur due to many other causes also. When we do exercises, our throat gets dry. Tension or production of less saliva by the salivary glands can also produce this effect. The question arises: why do we feel thirsty?
We know that water and salt are always present in our blood. The body tissues also contain these two substances. Under the normal conditions, the proportion of these two materials in blood remains constant. If due to some reason, the amount of water in blood gets reduced, the proportion of the two materials also changes. In such a situation the ‘thirst centre’ located in the brain sends signals to the throat. As a result of this the throat starts contracting. This contraction makes it dry and we start feeling thirsty, and so we drink water.
However, sometimes, the salivary glands secrete enough saliva and our stomach and blood too have enough water and yet we feel thirsty. For example, when man drinks liquor he takes enough quantity of salted preparations along with the drink. Though the amount of water goes increasing with the intake of liquor, yet consumption of salted foods increase the quantity of salt in blood. As a result of this the amount of salt in blood exceeds the normal level. This disturbs the normal proportion of salt and water in the blood. In such a situation we feel thirsty. Excessive thirst may be a symptom of diabetes or kidney ailments. In such cases immediate medical checkup should be undertaken.