Topic overview

Start with the big picture

Islet β-cells release insulin, which supports glucose uptake in muscle and adipose tissue, limits gluconeogenesis and other breakdown processes, and promotes storage and synthesis. During fasting, exercise, or hypoglycemia, α-cells release glucagon, increasing hepatic glucose output through glycogenolysis and gluconeogenesis. Their reciprocal actions help stabilize blood glucose. The lesson also outlines how glucose stimulates insulin secretion: rising ATP closes ATP-sensitive potassium channels, depolarizing the cell membrane and promoting calcium entry and insulin-vesicle release. Alongside this mechanism, it explores hormone patterns in fed and fasting states, the insulin-enhancing effects of GLP-1 and GIP, and clinical connections to diabetes mellitus and hypoglycemia.