arcuate nucleus
Summary
The arcuate nucleus is a hypothalamic cluster of neurons that senses hunger and satiety hormones in the blood. Ghrelin activates its appetite-stimulating neurons, while leptin and insulin inhibit those neurons and activate its appetite-suppressing ones.
Detail
Meaning: The arcuate nucleus sits at the base of the hypothalamus beside the third ventricle, where the blood-brain barrier is leaky enough for circulating hormones to reach it. It has two main neuron groups. NPY/AgRP neurons promote eating. POMC/CART neurons suppress it. Ghrelin, released by an empty stomach, activates the first group. Leptin, released by fat cells in proportion to fat stores, and insulin from the pancreas inhibit the first group and activate the second. The arcuate nucleus then signals other hypothalamic regions: the lateral hypothalamus (classic "hunger center") and the ventromedial hypothalamus (classic "satiety center").
On the MCAT: Expect a passage on leptin-deficient mice, a damaged leptin receptor, or a hormone injection into the hypothalamus. You predict the direction of change. Loss of leptin signaling in the arcuate nucleus gives increased eating and weight gain. After a meal, ghrelin falls, leptin and insulin rise, and appetite drops. In leptin resistance, leptin is high yet hunger persists.
Common confusion: Students swap the hormone directions or treat the arcuate nucleus as the lateral or ventromedial hypothalamus. Remember that ghrelin raises hunger, leptin lowers it, and the arcuate nucleus is the hormone-sensing stage that feeds those two regions.
Sources
- Principles of Neural Science
- Neuroscience
- Psychology
Written for the MCAT and checked before it was published. For study reference only. Spotted an error? Let us know.