What are the biological bases of hunger and thirst needs?

The biological bases of hunger and thirst needs are those which are indicated by events inside and outside the body.

Every organism has needs that produce drive and stimulate behaviour. It leads to certain actions towards achieving certain goals and reducing the drive.

The stimuli for hunger include stomach contractions, low concentration of glucose in the blood, nerve impulses sent by liver to the brain and external factors like aroma, taste and appearance of food.

Thirst occurs due to deprivation of water that leads to loss of water from cells and tissues of the body, drying of the mouth and subsequently causes dehydration. The anterior hypothalamus contains osmoreceptors that generate nerve impulses as a signal for thirst and drinking in case of cell dehydration.