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  • Hunger claws at your grumbling belly.

  • It tugs at your intestines, which begin to writhe, aching to be fed.

  • Being hungry generates a powerful, often unpleasant physical sensation that's almost impossible to ignore.

  • After you've reacted by gorging on your morning pancakes, you start to experience an opposing force, fullness, but how does your body actually know when you're full?

  • The sensation of fullness is set in motion as food moves from your mouth down your esophagus.

  • Once it hits your stomach, it gradually fills the space.

  • That causes the surrounding muscular wall to stretch, expanding slowly like a balloon.

  • A multitude of nerves wrapped intricately around the stomach wall sense the stretching.

  • They communicate with the vagus nerve up to the brainstem and hypothalamus, the main parts of the brain that control food intake.

  • But that's just one input your brain uses to sense fullness.

  • After all, if you fill your stomach with water, you won't feel full for long.

  • Your brain also takes into account chemical messengers in the form of hormones produced by endocrine cells throughout your digestive system.

  • These respond to the presence of specific nutrients in your gut and bloodstream, which gradually increase as you digest your food.

  • As the hormones seep out, they're swept up by the blood and eventually reach the hypothalamus in the brain.

  • Over 20 gastrointestinal hormones are involved in moderating our appetites.

  • One example is cholecystokinin, which is produced in response to food by cells in the upper small bowel.

  • When it reaches the hypothalamus, it causes a reduction in the feeling of reward you get when you eat food.

  • When that occurs, the sense of being satiated starts to sink in and you stop eating.

  • Cholecystokinin also slows down the movement of food from the stomach into the intestines.

  • That makes your stomach stretch more over a period of time, allowing your body to register that you're filling up.

  • This seems to be why when you eat slowly, you actually feel fuller compared to when you consume your food at lightning speed.

  • When you eat quickly, your body doesn't have time to recognize the state it's in.

  • Once nutrients and gastrointestinal hormones are present in the blood, they trigger the pancreas to release insulin.

  • Insulin stimulates the body’s fat cells to make another hormone called leptin.

  • Leptin reacts with receptors on neuron populations in the hypothalamus.

  • The hypothalamus has two sets of neurons important for our feeling of hunger.

  • One set produces the sensation of hunger by making and releasing certain proteins.

  • The other set inhibits hunger through its own set of compounds.

  • Leptin inhibits the hypothalamus neurons that drive food intake and stimulates the neurons that suppress it.

  • By this point, your body has reached peak fullness.

  • Through the constant exchange of information between hormones, the vagus nerve, the brainstem, and the different portions of hypothalamus, your brain gets the signal that you've eaten enough.

  • Researchers have discovered that some foods produce more long-lasting fullness than others.

  • For instance, boiled potatoes are ranked as some of the most hunger-satisfying foods, while croissants are particularly unsatisfying.

  • In general, foods with more protein, fiber, and water tend to keep hunger at bay for longer.

  • But feeling full won't last forever.

  • After a few hours, your gut and brain begin their conversation again.

  • Your empty stomach produces other hormones, such as ghrelin, that increase the activity of the hunger-causing nerve cells in the hypothalamus.

  • Eventually, the growling beast of hunger is reawakened.

  • Luckily, there's a dependable antidote for that.

Hunger claws at your grumbling belly.

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B2 H-INT US hypothalamus hunger stomach food brain sensation

【TED-Ed】How does your body know you're full? - Hilary Coller

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    詹士緯   posted on 2020/11/24
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