Grades 3–5 · Organisms
How do you know that you are hungry or getting full?
Hunger and fullness are experiences made by the brain using many kinds of information. The stomach is one source of messages, but it is not a perfect fuel gauge. A body can need energy while the stomach contains food, and smells or memories can also affect appetite.
In the diagramHunger and fullness use many messagesThe brain combines gut signals with other informationStomachBrainStretch signalsNo single organ is a perfect fuel-level gauge.
As food enters, the stomach wall stretches. Nerve signals help report that stretch. Cells in the digestive tract also release chemical messengers called hormones. Some help encourage eating; others contribute to a feeling of fullness as a meal is processed. Signals from stored body energy provide further information.
The brain combines these messages with taste, sight, smell, habits and emotion. No one message determines exactly how much a person will eat or when hunger will return. The diagram highlights a few routes into this conversation. It explains communication among organs, rather than assigning a food amount or judging someone’s appetite.
About this explanation
Starting knowledge: Know that nerves and chemical messages connect body parts.
Sources
- National Institute of Diabetes and Digestive and Kidney Diseases — Your Digestive System and How It Works
- NCBI Bookshelf, StatPearls — Physiology, Obesity Neurohormonal Appetite And Satiety Control