The startle reaction, also called startle response or alarm reaction, is the response of mind and body to a sudden unexpected stimulus, such as a flash of light, a loud noise, or a quick movement near the face. In human beings, the reaction includes physical movement away from the stimulus, a contraction of the muscles of the arms and legs, and often blinking. It also includes blood pressure, respiration, and breathing changes. The muscle reactions generally resolve themselves in a matter of seconds. The other responses take somewhat longer. An exaggerated startle reaction is called hyperexplexia (also hyperekplexia) The exaggerated startle response is often seen in patients with Post Traumatic Stress Disorder (PTSD).