Osmoreceptors sense a rise in blood osmolarity and antidiuretic hormone is released. Which class of stimulus triggered that release?

1. Humoral stimuli are changes in blood levels of non-hormone chemicals such as nutrients or ions. 2. Blood osmolarity is a measure of solute concentration, so a rise in it is a humoral change. 3. Hypothalamic osmoreceptors detect that change and prompt release of antidiuretic hormone. 4. A hormonal stimulus would need another hormone to be the trigger, and none is involved here. 5. A neural stimulus works through nerve impulses, as when sympathetic neurons drive the adrenal medulla. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 17 "The Endocrine System", section 17.2 Hormones_