Tectum

From Freepedia

The tectum is part of the brain that controls auditory and visual responses. It is located in the dorsal region of the mesencephalon (midbrain). It is composed of the inferior colliculi and the superior colliculi.

The tectum causes the spinal cord to respond reflexively to auditory and visual cues. Your eyes pick up that an object is coming at you, and instantly, you respond either by catching it, deflecting it or ducking. This happens without the realization that it is going on. In danger, the tectum won't wait to relay the message.