Which function is primarily controlled by the sympathetic nervous system?

The sympathetic nervous system is responsible for preparing the body for 'fight or flight' situations, which involves activating various physiological processes to respond to perceived threats or stressors. One of the primary functions of the sympathetic nervous system is the constriction of blood vessels, also known as vasoconstriction.

This process helps to redirect blood flow to vital organs and muscles that are critical for immediate survival, such as the heart and skeletal muscles, and away from non-essential systems during stressful times. By constricting blood vessels, the sympathetic nervous system increases blood pressure and enhances the availability of oxygen and nutrients to those muscles.

In contrast, relaxation of blood vessels would be associated with the parasympathetic nervous system, which promotes a state of rest and recovery. Increased peristalsis and salivation are also functions primarily regulated by the parasympathetic nervous system, focusing on digestion and rest rather than the active responses driven by the sympathetic nervous system.