The parasympathetic system is responsible for vegetative functions, uses the neurotransmitter acetylcholine, and has short postsynaptic nerves located near or on the organs they innervate. On the other hand, the sympathetic system is responsible for fight-or-flight functions, uses the neurotransmitter norepinephrine, and has relatively long postsynaptic nerves that synapse at a distance from the organs they innervate. Although the primary neurotransmitter released from sympathetic postganglionic neurons is norepinephrine, there are two important exceptions. These exceptions are the postganglionic neurons that innervate chromaffin cells of the adrenal medulla and those that innervate the sweat glands. When the postganglionic neurons that innervate sweat glands are activated, they release ACh (not epinephrine) which binds to muscarinic ACh receptors (mAChR: specifically the M1 and M3 receptors) on the target cell. Adrenal medullary chromaffin cells are functionally analogous to sympathetic postganglionic neurons and when stimulated by ACh from a sympthetic preganglionic neuron these cells release epinephrine and norepinephrine into the circulation. The receptors triggering the release of adrenal epinephrine and norepinephrine are nicotinic (nAChR).

In addition to the previous answer:

The effects of sympathetic and parasympathetic nerves are generally antagonistic; in a few cases, however, they can be complementary or cooperative. So, 1) the effects of sympathetic and parasympathetic stimulation on salivary gland secretion are complementary due stress\pain. The secretion of watery saliva is stimulated by parasympathetic nerves, which also stimulate the secretion of other exocrine glands in the digestive tract. Sympathetic nerves stimulate the constriction of blood vessels throughout the digestive tract. The resultant decrease in blood flow to the salivary glands causes the production of a thicker, more viscous saliva. 2)The effects of sympathetic and parasympathetic stimulation on the reproductive and urinary systems are cooperative. There is also cooperation between the two divisions in the micturition (urination) reflex. Although the contraction of the urinary bladder is largely independent of nerve stimulation, it is promoted in part by the action of parasympathetic nerves. This reflex is also enhanced by sympathetic nerve activity, which increases the tone of the bladder muscles. Emotional states that are accompanied by high sympathetic nerve activity (such as extreme fear) may thus result in reflex urination at bladder volumes that are normally too low to trigger this reflex.