Brain Tour : Our Brain : The Principal Part of the Brain :

Midbrain

The midbrain extends from the pons to the lower portion of the diencephlon. It contains a pair of tracts referred to as cerebral peduncles.

The cerebral peduncles contain motor fibres that connect the cerebral cortex to the pons and the spinal cord, and the sensory fibres that connect the spinal cord to the thalamus. The cerebral peduncles constitute the main connection for tracts between upper and lower parts of the brain and spinal cord. The nuclei for some cranial nerves originate in the midbrain.

The midbrain helps control sensory and motor functions such as eye movement and coordination of the visual and auditory reflexes.

Throughout the brain stem- medulla, pons, and midbrain, and diencephalon- is a group of widely scattered neurons what give a netlike (reticular) appearance and is referred to as the reticular formation. Neurones of the reticular formation receive and integrate input from the cerebral cortex, hypothalamus, thalamus, cerebellum and spinal cord. The neurones also send impulses to all levels of the central nervous system.

A severe blow to the mandible twists and distorts the brain stem and overwhelms the reticular formation by sending a sudden volley of nerve impulses to the brain, resulting in unconsciousness.