Final answer:
Insulin is secreted by the alpha cells of the pancreatic islets in response to high blood sugar. When blood glucose levels rise, beta cells in the pancreas release insulin to lower blood glucose levels.
Step-by-step explanation:
Insulin is secreted by the alpha cells of the pancreatic islets in response to When blood glucose levels rise, such as after a meal, beta cells in the pancreas release insulin to lower blood glucose levels by increasing the rate of glucose uptake in most body cells, and by increasing glycogen synthesis in skeletal muscles and the liver.