The central structures of the brain are the thalamus, hypothalamus, and pituitary gland. The thalamus relays sensory information to the cerebrum; the hypothalamus helps regulate body functions such as thirst and appetite, as well as sleep, aggression, and sexual behavior; and the pituitary gland produces hormones that play a role in growth, development, and various other physiological variables. The pons, medulla, and midbrain are the three structures that compose the brain stem. The ventricles are natural cavities inside the brain filled with cerebrospinal fluid.