Final answer:
A 25-year-old man with dilated pupils and a pounding heart may have ingested substances like norepinephrine or epinephrine, which are responsible for increasing heart rate and dilating pupils as part of the body's 'fight or flight' response.
Step-by-step explanation:
The symptoms described, such as dilated pupils and a pounding heart, indicate that the 25-year-old man might have ingested a stimulant that affects the sympathetic nervous system. Among the substances that cause such effects, norepinephrine and epinephrine (also known as adrenaline) are natural hormones but can also be ingested in synthetic forms. These compounds are responsible for the 'fight or flight' response, which can lead to an increase in heart rate, pupil dilation, and other physiological changes designed to prepare the body to confront or escape threats.
Norepinephrine and epinephrine increase blood pressure and heart rate, and norepinephrine, in particular, is also known to dilate the pupils. Both are linked to the endocrine system's response to stress, as seen in a scenario where someone experiences a traumatic event like a car accident. Beta-blockers, which can be prescribed for high blood pressure, work by blocking the receptors that respond to these hormones, therefore reducing heart rate and blood pressure.