The sympathetic nervous system is a part of the autonomic nervous system that prepares the body for stressful or emergency situations. It activates the "fight or flight" response, increasing heart rate, dilating airways, and redirecting blood flow to essential muscles. This response helps individuals react quickly to threats. When the sympathetic nervous system is activated, it releases hormones like adrenaline and noradrenaline, which enhance alertness and energy. This system works in balance with the parasympathetic nervous system, which promotes relaxation and recovery after stress. Together, they help maintain the body's overall stability and function.