Answer:
The Amygdala
Explanation:
The fear response starts in a region of the brain called the amygdala. This almond-shaped set of nuclei in the temporal lobe of the brain is dedicated to detecting the emotional salience of the stimuli – how much something stands out to us.
I used this site, if you would like to know more information please read it whenever you are free.
https://www.smithsonianmag.com/science-nature/what-happens-brain-feel-fear-180966992/