Blinking reflexes are controlled by a number of muscles. The orbicularis oculi and the levator palpebrae superioris muscles govern the opening and shutting of the upper eyelid. The orbicularis oculi muscle shuts the eye, whereas the levator palpebrae muscle contracts to open it. The third major group of muscles involved in the blinking mechanism is made up of the facial muscles. The mentalis muscle pulls the eyeball forward to blink, and the frontalis muscle raises the brow to blink. There are also small muscles behind the eyeball that are responsible for moving it back and forth during a blink. These muscles are not used to open or close the eye but rather to adjust its position. The orbicularis oculi is a flat muscle that covers most of the outer surface of the eye. It functions to open and close the eye. When you sleep at night, this muscle is very active because it is trying to keep the eye closed. As you wake in the morning, this muscle starts to relax if you are not making any sudden movements with your head, because it does not want anything to hurt your eye. If you continue to move your head around slowly, the orbicularis oculi will eventually get tired and not be able to shut your eye anymore.