Final answer:
Your racing heart and rapid breathing in response to being accused of stealing are due to your sympathetic nervous system, which activates the fight-or-flight response in stressful situations.
Step-by-step explanation:
The racing heart and rapid breathing triggered by an accusation of stealing money from your roommate are physiological responses mediated by your sympathetic nervous system. This part of the autonomic nervous system activates during stressful "fight or flight" situations. When faced with a perceived threat, such as an accusation, the body responds by releasing adrenaline, which leads to a faster heart rate, increased breathing, dilation of pupils, and other changes that prepare you to either confront the situation or evade it.
This is part of a broader fight-or-flight response that involves both the nervous and endocrine systems and is designed to prepare the body to handle emergencies or perceived dangers. This response is not only for physical threats but is also tied to strong emotional reactions and can be triggered in social or anxiety-inducing situations, as in the example of being accused by a roommate.