Humoral Stimuli
The term "humoral" is derived from the term "humour," which refers to bodily fluids, such as blood. A humoral stimulus refers to the control of hormone release in response to changes in extracellular fluids, such as the ion concentration in the blood. For example, a rise in blood glucose levels triggers the pancreatic release of insulin. Insulin causes blood glucose levels to drop, which signals the pancreas to stop producing insulin. This is an example of a negative feedback loop.