Many people have heard of the fight or flight response. It refers to a set of nerve and hormone si...
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Many people have heard of the fight or flight response. It refers to a set of nerve and hormone signals that cause physical changes to help us deal with danger. It is produced by a part of your nervous system that works automatically, called the sympathetic nervous system. When you encounter almost anything challenging, a tiny region at the base of your brain called the hypothalamus releases a hormone called corticoreleasing hormone, or CRH. This hormone travels a short distance to the pituitary gland at the base of the brain and triggers release of another hormone known as adrenocorticotropic hormone. This hormone, also known as ACTH, travels through your blood stream to your adrenal glands, located just above each of your kidneys. ACTH stimulates the adrenal glands to release epinephrine, also known as adrenaline, norepinephrine, and cortisol. Together, these hormones produce the physical changes associated with the fight or flight response. Your heart rate and breathing rate increase. The sweat glands on your skin become more active and your pupils dilate. Goosebumps occur when nerve signals cause tiny muscles attached to hair follicles to contract. The hair follicles rise above the rest of the skin, and these tiny elevations are what we call goose bumps.

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