Hunger and Satiety Hormones, B&B

CCK

Acts as both neurotransmitter and to close sphincter between the duodenum and stomach, causing stomach to hold its contents and fill up faster. Early satiety hormone, acting to end a meal; "here and now"

Leptin

Long-term hunger regulation accomplished by monitoring (subcutaneous) fat levels in the body. Fat cells produce this peptide, which signals the brain to either increase (in low levels) or decrease (in high levels; also results in high levels of physical and immune activity) eating. Thought to also be involved in long-term energy balance. Binds at arcuate nucleus and brain stem. Puberty is triggered by a certain level of this peptide. Giving this peptide does not simply cure obesity in most cases; the issue is typically that there are not enough receptors for it (obese people make plenty of this peptide normally).

Insulin

Pancreatic peptide hormone. In addition to increasing glucose decreasing glucose levels in the bloodstream, its effects are similar to the Leptin's except... Reflects VISCERAL fat (fat around organs). If receptors for this peptide are knocked out, the organism overeats and becomes fat because it cannot detect information about fat levels.

Ghrelin

Released as a neurotransmitter in the brain and a hormone in the stomach (to trigger stomach contractions). Potent apetite stimulant (growling). Increases the amount of food eaten, decreases energy expenditure, increases weight gain. Level rise 1-2 hours before a meal. Overproduction can lead to obesity (always hungry).

Orexin

Released by cells in the LH. Increases animal's persistence in seeking food. Responds to incentives and reinforcement in general. If we block receptors for this peptide, the animal is less likely to seek out and work for reward.

PYY

Satiety hormone released by intestinal cells. Increases upon ingestion of a meal and provides potent appetite-suppressing satiety (opposite of Ghrelin, similar to CCK). If injected into bloodstream or arcuate nucleus, curbs appetite. Chronically lowered in obsess people