Which physiological response is associated with the sympathetic nervous system during times of stress?

The sympathetic nervous system is primarily activated in response to stress through what is often referred to as the "fight or flight" response. When the body perceives a threat, several physiological changes occur to prepare for rapid action.

One of the most notable responses is the increase in heart rate and blood flow. This response ensures that more oxygen and nutrients are delivered to muscles and vital organs, enhancing physical performance and readiness to confront challenges. Additionally, blood vessels may constrict in non-essential areas to redirect blood to the muscles and brain, further supporting immediate physical activity.

Other options indicate physiological changes that occur during different states. Decreased heart rate and increased digestion efficiency are more characteristic of the parasympathetic nervous system, which promotes relaxation and restorative processes. The heightened immune response can occur but is not a direct primary response linked with acute sympathetic activation; rather, it may involve the complex interplay of various systems over a broader time frame.

Thus, the correct answer highlights the supportive role of the sympathetic nervous system in preparing the body for immediate physical action under stress, marked by increased heart rate and blood flow.