The parts of the midbrain that receive sensory input from visual systems and are involved in reflex movements of the head and eyes toward a stimulus (such as a sudden, bright light) are called colliculi.

The midbrain, also known as the mesencephalon, is a small region of the brain that serves as a relay center for visual, auditory, and motor system information. The midbrain is divided into two main parts: the tectum and the tegmentum.

The tectum contains two pairs of lobes, called the colliculi. These are the superior and inferior colliculi.

The superior colliculi are involved in preliminary visual processing and control of eye movements. When a sudden bright light is presented, the superior colliculi help direct the movement of the head and eyes toward the stimulus. This is a reflex movement, meaning it happens automatically without conscious thought.

The inferior colliculi are involved in auditory processing. They receive signals from the auditory nerve and help to process and perceive sounds.

So, in response to your question, the parts of the midbrain that receive sensory input from visual systems and are involved in reflex movements of the head and eyes toward a stimulus (such as a sudden, bright light) are called the superior colliculi.