Answer:
Adrenaline
Explanation:
Adrenaline, also called norepinephrine, is a hormone produced mainly by the adrenal glands (medulla). Its main goal is to prepare the body to “fight or flight” response, it means that under stressful situations (in this case, fear), it triggers heart rate increase, airway expansion (to benefit gas exchange), blood pressure increase, mydriasis, etc.
Adrenaline release is stimulated by the sympathetic nervous system.
