Arcuate Nucleus (ARC)

The arcuate nucleus is a critical collection of neurons located in the mediobasal hypothalamus, positioned adjacent to the third ventricle. This strategic location allows it to sense hormones and nutrients directly from the bloodstream, as the blood-brain barrier is somewhat more permeable in this region. The ARC is considered the primary 'sensing' station for the body's energy status, housing the essential neuronal populations that govern appetite and metabolism.

The ARC contains two antagonistic neuronal groups: the NPY/AgRP neurons, which stimulate hunger and promote energy conservation, and the POMC/CART neurons, which promote satiety and increase energy expenditure. These neurons project to other areas of the brain, such as the paraventricular nucleus, to execute complex behavioral and physiological responses to food intake. Dysfunction in the arcuate nucleus, often caused by inflammation or hormonal resistance, is a central feature of metabolic disorders and the survival shift.