The major regions of the midbrain are the tectum and the tegmentum. These parts of the brain and their divisions are responsible for motivation and the regulation of the auditory and visual systems.
The tectum is divided in to the superior colliculi and the inferior colliculi. These are found at the top of the midbrain.
The superior colliculi control a person's visual reflexes, and how he reacts when he sees movement. The inferior colliculi control a person's ability to hear.
Beneath the tectum is the tegmentum, which is divided into several parts.
The large and intricate reticular formation communicates with the thalamus, the cerebral cortex and the spinal complex. This is the part of the midbrain that controls sleep, arousal and the body's reflexes.
The periaqueductal grey matter controls the movements of primitive actions such as mating and fighting.
The red nucleus supports the coordination of the shoulders and the upper arms.
The substantia nigra is called such because of its abundance of melanin.The neurons in this area bond with dopamine. This is connected to the body's internal "reward" system. It also helps to control eye movement and plays a role in addiction.
The ventral tegmental area also contains cells that are dopaminergic as well as glutamate and GABA neurons. GABA is a neurotransmitter that inhibits the actions of nerve cells.