system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is that feeling we get in our stomach when we're hungry? Why does it happen?
gpt
Hunger is caused by a region in your brain called the hypothalamus, which regulates many different types of involuntary activities. The hypothalamus makes you feel full or hungry based on chemical hormone signals, nerve signals, and the type of food we last ate (more or less satiated for longer). Nerve signals from the stomach and small intestine detect pressure changes (distended or empty). Ghrelin stimulates secretion of neuropeptide Y which causes people to feel hungry; gherlin is released two hours after people eat and is associated with insulin levels.