Which physiological changes are associated with the activation of the sympathetic nervous system?

The activation of the sympathetic nervous system initiates the "fight or flight" response, preparing the body for increased physical activity and stress. One of the hallmark physiological changes during this activation is an increase in heart rate and blood flow. This is accomplished through the release of catecholamines, such as adrenaline, which stimulate the heart to beat faster and stronger, thereby increasing cardiac output. Additionally, blood vessels in the muscles dilate to improve blood flow, ensuring that the body is adequately supplied with oxygen and nutrients needed for rapid responses to perceived threats.

In contrast, options referring to increased digestive activity, decreased respiratory rate, and reduced blood pressure represent physiological changes typically associated with the parasympathetic nervous system, which is responsible for "rest and digest" activities. During sympathetic activation, digestive processes slow down, the respiratory rate typically increases to enhance oxygen intake, and blood pressure rises to support heightened activity levels.