What is the main function of the sympathetic nervous system?

The main function of the sympathetic nervous system is to activate the body's fight-or-flight response. This system prepares the body for stressful or emergency situations by triggering a series of physiological changes. When the sympathetic nervous system is activated, it can increase heart rate, raise blood pressure, dilate airways, and inhibit non-essential functions like digestion. This readiness to respond quickly to perceived threats is crucial for survival.

In contrast, the other functions listed are not primarily associated with the sympathetic nervous system. Regulation of sleep is predominantly managed by other parts of the nervous system, particularly the parasympathetic nervous system, which promotes relaxation and restorative processes. Enhancement of digestion is also a role of the parasympathetic nervous system, encouraging bodily functions that occur during rest and recuperation. Facilitation of relaxation is similarly aligned with the function of the parasympathetic nervous system, which counteracts the stress responses initiated by the sympathetic system.