<Tr> <Td> Penis </Td> <Td> Inhibits Tumescence </Td> </Tr> <Tr> <Td> Ductus deferens </Td> <Td> Promotes emission prior to ejaculation </Td> </Tr> <P> The sympathetic nervous system is responsible for up - and down - regulating many homeostatic mechanisms in living organisms . Fibers from the SNS innervate tissues in almost every organ system, providing at least some regulation of functions as diverse as pupil diameter, gut motility, and urinary system output and function . It is perhaps best known for mediating the neuronal and hormonal stress response commonly known as the fight - or - flight response . This response is also known as sympatho - adrenal response of the body, as the preganglionic sympathetic fibers that end in the adrenal medulla (but also all other sympathetic fibers) secrete acetylcholine, which activates the great secretion of adrenaline (epinephrine) and to a lesser extent noradrenaline (norepinephrine) from it . Therefore, this response that acts primarily on the cardiovascular system is mediated directly via impulses transmitted through the sympathetic nervous system and indirectly via catecholamines secreted from the adrenal medulla . </P> <P> The sympathetic nervous system is responsible for priming the body for action, particularly in situations threatening survival . One example of this priming is in the moments before waking, in which sympathetic outflow spontaneously increases in preparation for action . </P>

What are the effects of the sympathetic nervous system