Final answer:
The sympathetic nervous system increases heart rate, causes pupillary dilation, and triggers vasoconstriction, but does not cause pupillary constriction; that's a function of the parasympathetic nervous system.
Step-by-step explanation:
The sympathetic nervous system is responsible for the body's 'fight-or-flight' response during stressful situations. One of its functions is to increase heart rate to prepare the body for action. Another function includes triggering the dilation of pupils (pupillary dilation) to improve vision. In addition, it causes vasoconstriction, which is the narrowing of blood vessels to increase blood pressure. However, it does not normally cause vasodilation, which is the widening of blood vessels, as this would lower blood pressure and is not conducive to the fight-or-flight response. Therefore, the function that is NOT a part of the sympathetic nervous system is pupillary constriction, which is actually a function of the parasympathetic nervous system and works to decrease pupil size under rest-and-digest conditions.