Which of the following is an action of the sympathetic nervous system?

• A. Decreases respiratory rate
• B. Constricts pupils
• C. Stimulates digestion
• D. Increases heart rate

Answer: (D)

Verified step by step guidance

1. Understand the role of the sympathetic nervous system: It is part of the autonomic nervous system responsible for the 'fight or flight' response, preparing the body for stressful situations.
2. Identify the physiological changes associated with the 'fight or flight' response: These include increased heart rate, dilation of pupils, and inhibition of digestion, among others.
3. Analyze each option given in the problem: Decreases respiratory rate, Constricts pupils, Stimulates digestion, and Increases heart rate.
4. Relate each option to the sympathetic nervous system's actions: Decreasing respiratory rate and stimulating digestion are actions of the parasympathetic nervous system, which promotes 'rest and digest' activities.
5. Conclude that the correct action of the sympathetic nervous system from the options provided is 'Increases heart rate', as it aligns with the body's preparation for stress or danger.