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The experience of stress creates both an increase in general arousal in the sympathetic division of
the autonomic nervous system (ANS), as well as another, even more complex, system of
physiological changes through the HPA axis ((Reference None not found in Book)).
The HPA axis is a physiological response to stress involving interactions among the
hypothalamus, the pituitary, and the adrenal glands. The HPA response begins when the
hypothalamus secretes releasing hormones that direct the pituitary gland to release the hormone
ACTH. ACTH then directs the adrenal glands to secrete more hormones, including epinephrine,
norepinephrine, and cortisol, a stress hormone that releases sugars into the blood, helping
preparing the body to respond to threat (Rodrigues, LeDoux, & Sapolsky, 2009). [5]
Figure 10.9 HPA Axis
Stress activates the HPA axis. The result is the secretion of epinephrine, norepinephrine, and cortisol.