After feeding, and during the absorptive period, insulin is secreted by the B cells of the pancreas (Fig. 20.3) in response to nervous impulses that arise in the gut wall; to hormones that are liberated by endocrine cells in the intestinal mucosa; and to a rise in arterial glucose concentration. This has the effect of decreasing glucose output by the liver and increasing its uptake and conversion to glycogen, increasing outflow from the glucose pool into glucose-dependent tissues and producing a positive arteriovenous glucose difference across the forearm and other peripheral tissues.
