The hypothalamus consists of a cluster of small but critical nucleii; located inferior to the thalamus, just posterior to the optic chiasm and forming the floor of the 3rd ventricle. It includes (anatomically) the optic chiasm, mammilary bodies, infundibulum, and pituatary gland. It's function is to integrete the activities of the autonomic,endocrine, and limbic systems,by helping to maintain homeostasis. It also controls the regulation of temperature, appetite, sexual drive, and sleep patterns. It  modulates activities of the pituatary gland by releasing neurohormones that control the pituatary's release fo hormones.