The insulin concentration in blood increases after meals and gradually returns to basal levels during the next 1–2 hours.
However, within an islet of Langerhans the oscillations become synchronized by electrical coupling between closely located beta cells that are connected by gap junctions, and the periodicity is more uniform (3-6 min).
[1] Pulsatile insulin release from the entire pancreas requires that secretion is synchronized between 1 million islets within a 25 cm long organ.
Much like the cardiac pacemaker, the pancreas is connected to cranial nerve 10, and others, but the oscillations are accomplished by intrapancreatic neurons and do not require neural input from the brain.
Pulsatile insulin delivery to the portal vein or islet cell transplantation to the liver of diabetic patients are therefore attractive therapeutic alternatives.
[1] "Chapter 12: Electrical Bursting, Calcium Oscillations, and Synchronization of the Pancreatic Islets by Richard Bertram, Arthur Sherman, and Leslie S Satin".