Parasympathetic and sympathetic refer to the two branches of the

Parasympathetic and Sympathetic refers to two branches of the Autonomic Nervous System (ANS).

The Parasympathetic Nervous System (PNS) has a general function of controlling bodily functions such as homeostasis and the body's response during rest.

The Sympathetic Nervous System (SNS) on the other hand refers to the body's response to perceived danger.

Each of these result in different bodily responses.  In the case of the PNS these include: a decreased heart rate, bronchial tube constriction, relaxation of muscles and the constriction of th pupils.  When it comes to the SNS, these responses include: increased cardiovascular contraction (leading to an increased heart rate), dilation of the bronchial tubes, contraction of muscles and dilation of the pupils/