Glucagon and the a Cell: Physiology and Pathophysiology

Signals to Islet Cells External Signals The islets achieve their physiologic goals through appropriately timed and quantitated responses to signals that inform them about events taking place else-where in or near the body. These signals reach the islet cells by way of the circulation (nutrients and hormones) and the autonomic nervous system (norepinephrine, acetylcholine, and probably certain neuro-peptides).⁶⁰ In steady and relatively unstressed states (basal and near-basal states and even famine) it seems likely that the glucose level or unidentified controls or both maintain the required levels of insulin and glucagon. By contrast, whenever the steady state is acutely perturbed,.