Answer:
Sympathetic nervous system
Step-by-step explanation:
Pat is home alone one night and hears her doorbell ring. She is not expecting a visitor and her heart starts to beat quickly. Pat's Sympathetic nervous system has been activated by this unexpected visitor and it will produce hormones involved in her stress response.
Sympathetic nervous system is place which reacts in response to quick shocks or or the body's involuntary movements to situations and reacts in the form of producing stress hormones. It increases the blood flow to the muscles due the sudden involuntary actions.