Hyperarousal

• Trauma over-stimulates the nervous system, leaving survivors feeling permanently "on edge" ("hyperarousal"). 
• They "jump" at the slightest noise.
• Sometimes as they are about to fall asleep, they experience a dramatic "twitch" or "start".  This is called a nocturnal myoclonic jerk. (It is harmless.)
  

Hyperacusis

• Certain noises may also seem to be more vivid than usual. 

Hypervigilance 

• This is a related reaction which means that the individual displays a heightened and to some extent exaggerated sense of personal risk (e.g., a rape victim who never felt safe walking alone at any time of the day or night, and could never remain alone in the company of men, whether or not she knew them. 
• This level of anxiety in such circumstances may trigger a "panic attack").