sympathetic nervous system (thing)

Forming part of the autonomic nervous system, the sympathetic nervous system innervates every part of the body and drives the "fight or flight" response. It generally opposes the action of the parasympathetic nervous system

Examples of sympathetic effects:

• dilates pupil
• increases heart rate
• dilates air passages in lung
• reduces gut motility
• increases blood glucose level
• reduced urine output
• sweating
• shunting of blood to vital organs (skin turns pale, blood to gut is cut off, blood only goes to brain, heart, necessary muscles)
• piloerector muscles (raise hair and goosebumps)

note: Ejaculation is sympathetic

more info: http://gwis2.circ.gwu.edu/~atkins/Neuroweb/sympathetic.html