You are studying alone in your room late at night when you hear a loud noise downstairs. Your heart beat has increased significantly and your breathing is deeper. You wonder if a burglar has entered the house so you decide to investigate. When you cautiously walk downstairs you discover your cat has knocked over a plant stand. Your body begins to relax and return to normal. Which part of your nervous system is responsible for returning you to a normal state

The parasympathetic nervous system (PNS) is one of the three divisions of the autonomic nervous system. The PNS rests and relaxes the body after it is at a heightened state of arousal (usually due to the fight and flight system being activated). The PNS is responsible for returning heart beat back to a normal rate, slowing down rapid breathing, relaxing muscles, constricting pupils and relaxing the digestive and excretory system so that they return to normal functioning. 

the electromagnetic spectrum includes, from longest wavelength to shortest: radio waves, microwaves, infrared, optical, ultraviolet, x-rays, and gamma-rays.