Ch. 9.3. Hunger Flashcards
Why do most Southeast Asian adults avoid drinking much
milk?
Most Southeast Asian adults lack the genes that help digest lactose, the main sugar in milk.
What evidence indicates that taste is not sufficient for
satiety?
Animals that sham-feed chew and taste their food but do not become satiated.
What evidence shows that stomach distension is sufficient for satiety?
If a cuff is attached to the junction between the stomach and duodenum so that food cannot leave the stomach, an animal becomes satiated when the stomach is full.
What are two mechanisms by which cholecystokinin (CCK) increases satiety?
When the duodenum is distended, it releases CCK, which closes the sphincter muscle between the stomach and duodenum. CCK therefore increases the rate at which the stomach distends. Also, neural signals from the intestines cause certain cells in the hypothala- mus to release CCK as a neurotransmitter, and at its receptors, it triggers decreased feeding.
Why do people with very low insulin levels eat so much?
Those with very low levels, as in type 1 diabetes, can- not get glucose to enter their cells, and therefore, they are constantly hungry. They pass much of their nutrition in the urine and feces. Those with constantly high levels deposit much of their glucose into fat and glycogen, so within a short time after a meal, the supply of blood glucose drops.
What would happen to someone’s appetite if insulin levels and glucagon levels were both high?
When glucagon levels rise, stored glycogen is converted to glucose, which enters the blood. If insulin levels are high also, the glucose entering the blood is free to enter all the cells. So the result would be decreased appetite.
Why are leptin injections less helpful for most overweight
people than for mice with a mutation in the leptin gene?
Those mice fail to produce leptin. Nearly all over- weight people produce enough leptin, and extra leptin only weakly suppresses appetite.
Name three hormones that increase satiety and one that increases hunger.
Insulin, CCK, and leptin increase satiety.
Ghrelin increases hunger.
Which neuropeptide from the arcuate nucleus to the paraventricular nucleus is most important for satiety?
Melanocortin
In what ways does the lateral hypothalamus facilitate feeding?
Activity of the lateral hypothalamus improves taste, enhances cortical responses to food, and increases secre- tions of insulin and digestive juices.
In what way does eating increase after damage in and around the ventromedial hypothalamus? After damage to the paraventricular nucleus?
Animals with damage to the ventromedial hypothalamus eat more frequent meals. Animals with damage to the para- ventricular nucleus of the hypothalamus eat larger meals.
Why did the Pima people begin gaining weight in the mid-1900s?
They shifted from a diet of local plants that were seasonally available to a calorie-rich diet that is available throughout the year.
For someone who is trying to lose weight, why would it be a
good idea to cut down on sweets altogether?
Sugars provide many calories. Although fructose pro- vides fewer calories for a given amount of sweet taste, it is less effective at triggering a sense of satiety. People who try to satisfy their sweet cravings with artificial sweeteners do not generally cut down on total calories. Furthermore, arti- ficial sweeteners promote the types of intestinal bacteria that are associated with type 2 diabetes.
What evidence from rats suggests that bulimia resembles an addiction?
Rats that alternate between food deprivation and a very sweet diet gradually eat more and more, and they react to deprivation of the sweet diet with head shaking and teeth chattering, like the symptoms of morphine withdrawal.
If rats are limited to eating for one hour a day, what determines whether or not they will lose weight?
If the room is cool and the rats have access to a running wheel, they will exercise enough to keep warm, which is also enough to force them to lose weight.
