Glia is the supportive tissue of the brain. The most common glial cells are astrocytes and oligodendrocytes. Unlike nerves, glia can reproduce itself. Glia is the origin of the largest percentage of brain tumors. Astrocytes are involved with the blood brain barrier and brain metabolism.
Oligodendrocytes maintain the myelin covering of nerve cells.
Myelin helps transmit information between nerve cells. The hypothalamus makes up part of the wall of the third ventricle and is the base of the optic chiasm. The limbic system, together with the hypothalamus, controls hunger, thirst, emotional reactions, and biological rhythms. It is also involved with the endocrine and autonomic motor systems. The medulla oblongata, a part of the brain stem, connects the brain with the spinal cord.