Nancy is in her building elevator going down to the lobby when the elevator stops suddenly between floors, and the doors won't open. nancy's heart starts pounding, and her palms start sweating. in this scenario, nancy's physiological responses can be best attributed to her nervous system.

Sympathetic nervous system

Explanation:

The sympathetic nervous system is a component of the autonomic nervous system that is responsible for the involuntary actions of the body, such as breathing, heart rate, and digestion.  

The sympathetic nervous system is responsible for the body’s reaction to threat or distress by initiating "fight-or-flight" responses which are mostly physiological.

As Nancy perceives a threat to her safety, causing her to worry the more, the part of her brain called amygdala sends across a distress signal to the hypothalamus. The hypothalamus then sends a signal to the autonomous nervous system, which activates the sympathetic nervous system, prompting the adrenal glands to secrete the epinephrine hormone. The secretion of this hormone into the blood system is what initiates the several physiological responses exhibited by Nancy which are termed "fight-or-flight" responses.