Final answer:
The statement that the gut peptides PYY, GLP-1, and CCK act at the brain to signal satiety is true. They are involved in intricate appetite-regulating networks, interacting with the hypothalamus to modulate food intake and convey feelings of fullness.
Step-by-step explanation:
It is true that the gut peptides PYY, GLP-1, and CCK also act at the brain to signal satiety. These peptides are key players in the complex regulation of appetite and food intake. These substances are released after eating and interact with the hypothalamus region of the brain, which is critical for controlling hunger and satiety signals. PYY, short for peptide YY, slows down gastric emptying and stimulates appetite-reducing circuits within the brain. GLP-1, or glucagon-like peptide-1, enhances the secretion of insulin and promotes a feeling of fullness. CCK, or cholecystokinin, helps in digestion and also signals satiety to the brain by acting on CCK receptors.
The secretion of these peptides leads to the sensation of fullness and satisfaction, known as satiation, and signals the cessation of eating behaviors. They work as part of an intricate network of signals involving the gastrointestinal tract, the pancreas, and the liver, all of which contribute to the regulation of food intake. Throughout this process, as blood glucose levels rise, various hormonal responses collaborate to shut off hunger and encourage the stopping of eating.