The fight or flight response is activated by danger, fear, and stress. The fight or flight response is caused by both the release of stress hormones and the activation of the sympathetic nervous system. So the fight or flight response is both a hormonal response and a neural response.
When you are stressed, the amygdala in the brain is activated, and it signals the hypothalamus to release CRF (corticotropin releasing factor) which then travels to the pituitary. The pituitary in turn releases ACTH (adrenocorticotropic hormone) which travels to the adrenal glands. The adrenal glands subsequently releases cortisol, which is a stress hormone involved in the fight or flight response.
Also when you are stressed, the amygdala activates the locus coeruleus, which then activates the sympathetic nervous system. The sympathetic nervous system innervates the major body organs, and makes you breathe faster, heart beat faster, dilate pupils, increase blood blow, increase perspiration, and increase muscular tension. In addition, the sympathetic nervous system also triggers the adrenal glands to release adrenaline, which also duplicates and exaggerates the sympathetic nervous system response of increased heart rate, increased blood flow, etc.
So the fight or flight response is caused by the activation of the sympathetic nervous system and the release of stress hormones which include adrenaline and cortisol. For more information on the fight or flight response, please click here.
