1. When food is almost digested in the stomach, gastric juice continues to secrete. Because the stomach is empty, the contraction of the stomach is gradually strengthened. The impulse of intense contraction on an empty stomach is transmitted to the brain through nerves, causing hunger. We call this violent gastric contraction hunger contraction.

2. When the stomach is hungry and contracts, the liquid in the stomach and the swallowed gas are restless in the stomach, and they are squeezed eastward and westward for a while, and the result will be a "goo goo" sound.

3. Hunger contraction is cyclical. When you are hungry, the severe contraction of the stomach lasts only about half an hour, and then you enter a quiet period.

Extended data

Hunger persists and enters a state of chronic hunger. In addition to the above biochemical and metabolic characteristics, the human body will also have the following changes:

① Fat mobilization and ketone body production and utilization were further strengthened, protein decomposition was reduced, and blood sugar level was maintained.

② The negative nitrogen balance in pre-starvation period was relieved, and the urine nitrogen content dropped to a relatively stable low level.

③ The utilization of ketone bodies is enhanced, especially in the brain.

④ The gluconeogenesis of kidney is obviously enhanced, almost equal to that of liver, and the glutamine released by kidney is increased. The amide nitrogen and amino nitrogen released by glutamine promote the discharge of hydrogen ions in the form of ammonia, thus improving ketosis and acidosis.

Baidu Encyclopedia: Digestive System