THALAMUS AND HYPOTHALAMUS
The forebrain subdivides to form the telencephalon and diencephalon. The telencephalon gives rise to the cerebrum; the diencephalon gives rise to the thalamus and hypothalamus.

In mammals, the thalamus receives all sensory messages from the spinal cord (except those from the olfactory receptors) prior to being directed to the cerebrum's sensory areas. The function of the thalamus is to sort and interpret these messages before relaying them to the appropriate neurons in the cerebrum.

Lying just beneath the thalamus, the hypothalamus forms the floor of the third ventricle. The hypothalamus contains olfactory centers and is the main integration hub for controlling the viscera (internal organs). It supplies input to areas in the medulla and spinal cord that control activities such as heart rate, respiration, and fat metabolism. In reptiles, birds, and mammals, the hypothalamus regulates body temperature. It also controls appetite and water balance and plays a part in emotional and sexual responses. The hypothalamus is the bridge between the nervous and endocrine systems. It produces various hormones and regulates the pituitary gland.