What reaction is triggered by the sympathetic nervous system?

The reaction triggered by the sympathetic nervous system is best characterized by the "fight or flight" response. This physiological reaction prepares the body to either confront or flee from perceived threats. When the sympathetic nervous system is activated, several changes occur in the body to support this response.

One of the primary effects is an increase in heart rate and blood pressure. This increase in cardiovascular activity allows for enhanced blood flow to muscles and vital organs, thereby providing the necessary oxygen and nutrients to support immediate physical performance. Other responses include dilation of the airways to improve oxygen intake, mobilization of energy stores, and heightened alertness, all of which are critical for responding to stressors.

In contrast, components of the other choices do not accurately reflect the role of the sympathetic nervous system. The rest and digest response is associated with the parasympathetic nervous system, which promotes a state of calm and reduced heart rate. Similarly, the calm and recovery state and increased energy with heightened sensory awareness can also be attributed to parasympathetic functions and are not direct responses driven by sympathetic activation.