The Stress Response

When someone confronts an oncoming danger, the eyes or ears (or both) send the information to the amygdala, an area of the brain that contributes to emotional processing. When it perceives danger, it instantly sends a distress signal to the hypothalamus.

The hypothalamus activates the sympathetic nervous system by sending signals through the autonomic nerves to the adrenal glands. These glands respond by pumping the hormone epinephrine (also known as adrenaline) into the bloodstream. As epinephrine circulates through the body, it brings on a number of physiological changes.