The brainstem is made up of all the unpaired structures that connect the cerebrum with the spinal cord. Most rostral in the brainstem are structures often collectively referred to as the diencephalon. These structures are the epithalamus, the thalamus, the hypothalamus, and the subthalamus. Directly beneath the diencephalon is the midbrain, or mesencephalon, and beneath the midbrain are the pons and medulla oblongata, often referred to as the hindbrain. The epithalamus is represented mainly by the pineal gland, which lies in the midline posterior and posterior to the third ventricle. This gland synthesizes melatonin and enzymes sensitive to daylight. Rhythmic ...(100 of 37287 words)