- The intake of nutrients is under intricate control. A number of statements are made about factors controlling food intake:
(A) Cholecystokinin produced from small intestine stimulates food intake
(B) Leptin produced in adipose tissues stimulates food intake
(C) Leptin receptors are located in hypothalamus
(D) Ghrelin produced in the stomach inhibits food intake
(E) Leptin also stimulates the metabolic rate
(F) Ghrelin increases secretion of Neuropeptide Y
Choose the combination of all correct statements from the following options:
(1) A, B and C (2) A, B and D
(3) D, E and F (4) C, E and F
Hormonal Control of Food Intake: Clarifying Roles of Cholecystokinin, Leptin, and Ghrelin
Food intake is regulated by a complex network of hormones and peptides that communicate signals about hunger, satiety, and energy stores to the brain, primarily the hypothalamus. Key players include cholecystokinin (CCK), leptin, and ghrelin, each with distinct roles in appetite modulation and metabolism.
Evaluating the Proposed Statements
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(A) Cholecystokinin produced from the small intestine stimulates food intake:
False. Cholecystokinin (CCK) is a satiety hormone that inhibits food intake. It is released after eating and promotes feelings of fullness. -
(B) Leptin produced in adipose tissues stimulates food intake:
False. Leptin is produced by fat cells and acts to suppress appetite, signaling adequate energy stores. -
(C) Leptin receptors are located in the hypothalamus:
True. Hypothalamic neurons possess leptin receptors, through which leptin influences appetite and energy expenditure. -
(D) Ghrelin produced in the stomach inhibits food intake:
False. Ghrelin is known as the “hunger hormone” because it stimulates food intake. -
(E) Leptin also stimulates the metabolic rate:
True. Leptin increases energy expenditure by stimulating metabolic rate alongside suppressing appetite. -
(F) Ghrelin increases secretion of Neuropeptide Y:
True. Ghrelin promotes the release of neuropeptide Y (NPY), which enhances appetite and reduces energy expenditure.
Correct Combination from the Options
The statements that are correct are:
-
C: Leptin receptors in the hypothalamus
-
E: Leptin stimulates metabolic rate
-
F: Ghrelin increases secretion of Neuropeptide Y
Thus, the correct combination is:
(4) C, E and FSummary Table: Hormones and Their Effects on Food Intake
Hormone Site of Production Effect on Food Intake Other Effects Cholecystokinin (CCK) Small intestine Inhibits (satiety) Stimulates digestion, slows gastric emptying Leptin Adipose tissue Inhibits Increases metabolic rate Ghrelin Stomach Stimulates Increases NPY secretion Conclusion
Contrary to some misconceptions, CCK and leptin inhibit food intake, whereas ghrelin stimulates hunger. Leptin acts not only to reduce appetite but also to raise metabolic rate. Ghrelin stimulates neuropeptide Y, a potent appetite enhancer. Recognizing these physiological actions clarifies how the body intricately controls food consumption.
Therefore, the correct answer is:
(4) C, E and F -
