AP PSYCHOLOGY

Detailed explanation-1: -Ghrelin, a hormone produced by the stomach, triggers the release of orexin from the hypothalamus, signalling to the body that it is hungry.

Detailed explanation-2: -Orexin peptides are synthesized and secreted by a group of neurons mostly localized in the lateral hypothalamus including the perifornical area. Small groups of orexin neurons also found in the posterior hypothalamic area and dorsomedial hypothalamic nucleus.

Detailed explanation-3: -Crucial evidence indicates that orexin-A increases food intake by delaying the onset of a behaviourally normal satiety sequence. In contrast, a selective orexin-1 receptor antagonist (SB-334867) suppresses food intake and advances the onset of a normal satiety sequence.

Detailed explanation-4: -Orexins are also known as hypocretins, and were originally identified as appetite-stimulating peptides produced in the lateral hypothalamus (LH). Subsequent research has indicated that orexin is extensively involved in the physiological processes of the sleep–wake cycle, analgesia, alcoholism, learning, and memory.

Detailed explanation-5: -Orexins (also known as hypocretins) were identified as endogenous ligands for two orphan G-protein-coupled receptors in the lateral hypothalamic area. They were initially recognized as regulators of feeding behavior, but they are mainly regarded as key modulators of the sleep/wakefulness cycle.