Which of the following is an example of an expected response to sympathetic nervous system stimulation?

• A. Decreased heart rate
• B. Pupillary constriction
• C. Slower digestion
• D. Increased heart rate

Answer: (D)

When the sympathetic nervous system is activated, the body prepares for action—the fight-or-flight response. A key effect is increasing heart rate to boost blood flow to muscles and vital organs. This is achieved by beta-adrenergic receptors in the heart, which raise the rate and force of heartbeats.

Among the options, an increased heart rate is the clearest, most direct example of a sympathetic response. Decreased heart rate is a parasympathetic effect. Pupillary constriction is parasympathetic. Slower digestion is a sympathetic effect, but the most characteristic and commonly tested single sign of sympathetic activation is the rise in heart rate.