USA Biology Olympiad (USABO) Practice Exam

Which of the following is not a function of the parasympathetic division of the nervous system?

1. Stimulation of the adrenal medulla

2. Increased gastrointestinal activity

3. Decreased heart rate

4. Pupil constriction

The correct answer is: Stimulation of the adrenal medulla

The correct answer highlights a key distinction between the functions of the parasympathetic and sympathetic divisions of the nervous system. The parasympathetic division, often described as responsible for "rest-and-digest" functions, plays a significant role in promoting activities that occur during restful states. This includes increasing gastrointestinal activity to aid digestion, decreasing the heart rate to conserve energy, and stimulating pupil constriction to enhance near vision and focus on surrounding details. In contrast, stimulation of the adrenal medulla is primarily a function of the sympathetic nervous system. The adrenal medulla, when activated, releases adrenaline and noradrenaline, hormones that prepare the body for "fight-or-flight" responses. This process increases heart rate, redirects blood flow to muscles, and generally prepares the body for rapid action, which is contrary to the calming, restorative functions of the parasympathetic division. In summary, while the parasympathetic division enhances digestive functions, reduces heart rate, and constricts pupils, it does not stimulate the adrenal medulla, which aligns with the physiological demands of stress or emergency situations handled by the sympathetic system.