Upon being stimulated by fear or anger, the adrenal medulla automatically injects the hormone epinephrine (adrenaline) directly into the blood stream, the "adrenaline dump." This can have numerous effects on the body, including:
- Increased heart rate (200 to 300 beats per minute) and increased blood pressure, which may cause fainting; and the body may constrict itself into a fetal position in preparation for a coma.
- Dilation of the bronchial passages, permitting higher absorption of oxygen.
- Dilated pupils to allow more light to enter.
- Visual exclusion (tunnel vision) occurs, allowing greater focus but resulting in the loss of peripheral vision.
- Release of glucose into the bloodstream, generating extra energy by raising the blood sugar level.
- Auditory exclusion, or enhancement, of hearing.
- Increased pain tolerance.
- Loss of color vision.
- Short-term memory loss.
- Dry mouth.
- Tingling sensations.
- Urge to urinate and defecate.
- Decreased fine motor skills.
- Decreased communication skills.
- Decreased coordination.
The distorted perception of time, as well as the partial color blindness and tunnel vision, cause people to have serious misinterpretations of their surroundings, causing them to take seemingly inappropriate actions. Temporary paralysis may occur, momentarily causing you to freeze as your body desperately tries to catch up to the sudden awareness that your life is in danger. The severe lack of adrenaline after an event may mimic post-traumatic stress disorder, where people may appear extremely emotional and overly tired, regardless of their actual physical exertion.