Answer:
Endocrine and Nervous system
Step-by-step explanation:
Endocrine and Nervous system
The nervous system is what is responsible for the fight or flight response in every living animal, and so that is one of the major body systems everyone should think of when the body is enacting a stress response to a stimulus.
The SNS (Sympathetic Nervous System) also releases instruction to flood the body with hormones like adrenaline to help the animal either fight or run.
The endocrine however signals to the pituitary gland in the brain to increase the production of Cortisol (Stress hormone), otherwise known as a steroid hormone that regulates a lot of other body system as well, the Cortisol is another large factor in Fight or Flight response.
I hope this helps!