Hypothalamic regulation of appetite and satiety
Core concept
- Arcuate nucleus (ARC) is the integrating centre - sits at the median eminence, a circumventricular organ outside the blood-brain barrier, so it samples circulating hormones directly
- Two reciprocally inhibitory first-order populations
- NPY / AgRP - orexigenic; inc feeding, dec energy expenditure; also GABAergic onto POMC neurons
- POMC / CART - anorexigenic; POMC cleaved to alpha-MSH
- Second-order relay = the melanocortin pathway
- alpha-MSH -> MC4R in the paraventricular nucleus (PVN) -> satiety, inc sympathetic outflow
- AgRP is an inverse agonist at MC4R - it actively drives tone below baseline, not merely competes
- Classic lesion physiology (still examined)
- VMH = satiety centre - lesion -> hyperphagia, obesity
- LHA = hunger centre - lesion -> aphagia, wasting
- "VMH = Very Much Hungrier"
- Ghrelin is the only orexigenic circulating hormone; leptin, insulin, PYY, GLP-1, CCK, amylin all anorexigenic
3 more sections, plus exam facts
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