How do Beta Cells secrete insulin to decrease blood glucose concentration?

Blood glucose enters the beta cells by facilitated diffusion. The increased concentration of glucose in the beta cell causes the rate of respiration to increase therefore produces more ATP. The rise of ATP triggers the potassium ion channels in the plasma membrane of the beta cell to close. Potassium ions then build up inside the cell and this causes the plasma membrane to depolarise. Depolarisation triggers the calcium ion channels to open and the influx of calcium ions causes vesicles that contain the insulin to fuse to the plasma membrane. This is called exocytosis. Insulin is then released into the blood.