Which of the following effects are mediated by the parasympathetic nervous system?

• A. Release of glucose into the bloodstream by the liver
• B. Secretion of epinephrine and norepinephrine by the adrenal glands
• C. Bronchiole dilation
• D. Stimulation of the digestive system

Answer: (D)

The parasympathetic system drives “rest and digest” activities, turning focus to digestion and energy storage. It increases digestive secretions (saliva, gastric juice, pancreatic enzymes), enhances smooth muscle activity and peristalsis in the gut, and supports blood flow to the digestive tract. That’s why stimulation of the digestive system is the effect mediated by this system.

The other options reflect responses more typical of the sympathetic system: releasing glucose from the liver to raise blood sugar (glycogenolysis) during stress; triggering adrenal medulla secretion of epinephrine and norepinephrine; and dilating bronchioles (which is actually a sympathetic effect).