The diencephalon is a small structure of the brain, superior to the brainstem and surrounded by cerebral hemispheres. It’s a crucial site for relaying impulses and controlling the autonomic nervous system. It’s also the area that regulates body temperature, hunger, thirst, emotional patterns, and a 24-hour natural body cycle called the circadian rhythm.
The diencephalon consists of many smaller parts, the two most important are the thalamus and hypothalamus. The thalamus relays sensory impulses towards the cerebrum.
The hypothalamus is small, about the size of an almond, and sits above your brainstem. It is below (hypo) the thalamus. It has various functions; it controls the autonomic nervous system, regulates body temperature, hunger, and thirst, and also produces two hormones: ADH and oxytocin. The hypothalamus is also a commander of the pituitary gland, which releases essential hormones.
Figure 1: Major regions of the brain