Sympathetic nervous system

The sympathetic nervous system is part of the autonomic nervous system has the following functions:

The autonomic nervous system
Blue = parasympathetic
Red = sympathetic

Diverts blood flow away from the gastro-intestinal (GI) tract and skin via vasoconstriction.
Blood flow to skeletal muscles, the lung is not only maintained, but enhanced (by as much as 1200%, in the case of skeletal muscles).
Dilates bronchioles of the lung, which allows for greater alveolar oxygen exchange.
Increases heart rate and the contractility of cardiac cells (myocytes), thereby providing a mechanism for the enhanced blood flow to skeletal muscles.
Dilates pupils and relaxes the lens, allowing more light to enter the eye.

See also