Which of the following is a characteristic of the sympathetic nervous system?

The sympathetic nervous system is primarily responsible for the "fight or flight" response, which prepares the body to react to stressful situations. One of the hallmark characteristics of this system is the increase in heart rate, which enhances the delivery of oxygen to muscles and vital organs during times of stress or danger. This increased heart rate is achieved through the release of catecholamines, such as adrenaline, which stimulate the heart to beat more forcefully and rapidly.

In contrast, decreased heart rate, vasodilation, and relaxation of the body are associated with the parasympathetic nervous system, which works to conserve energy and promote resting functions after a stressful event. The parasympathetic system slows the heart rate, causes blood vessels to dilate in specific regions, and promotes a state of calm and relaxation in the body. Understanding these distinctions is crucial for recognizing how the two branches of the autonomic nervous system function in different physiological contexts.