system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what causes our stomach to "rumble" when we are hungry?
gpt
The rumble is called peristalsis, it's a movement your intestines constantly do in order to move food along your body.  It originates in your stomach then moves down your gastrointestinal tract to the sphincter.  The frequency depends on the fullness of your stomach, an organ which is able to gauge how much food there is and tell your brain.  When you're 'hungry' your organs notice not only a lack of food, but more importantly a lack of nutrients.  Your peristalsis cycles fire faster, up to rate of 1 every 10 minutes.  You actually can listen to this muscle movement with a stethoscope, but the audible rumbles come from simply the right conditions of hollow intestines and a strong enough muscular stimulation.