The hypothalamus (from the Greek words meaning “chamber underneath”) is a structure with a variety of vital functions that links the nervous system to the endocrine system via the pituitary gland, for the regulation and coordination of basic life functions. The hypothalamus, as the name would suggest, is located below the thalamus and above the brainstem. It receives sensory inputs that detect changes in both internal and external environments. It receives direct inputs from smell, taste, visual, and somatosensory systems and also senses blood temperature, blood sugar, mineral levels, and a variety of hormones. The hypothalamus is closely connected to other limbic structures such as the hippocampus, amygdala, and cingulate cortex, and thus forms part of the continuum of emotional responsiveness. The medial zone of the hypothalamus is involved in motivated behaviours such as defensive behaviours.

The hypothalamus acts as a control centre for certain metabolic processes and activations of the autonomic nervous system involved in fluid and electrolyte balance, energy metabolism, circadian rhythms, sleep, fatigue, thirst, body temperature, hunger, attachment behaviours (including sexual and reproductive behaviour), to name a few. It synthesizes and secretes certain neurohormones that stimulate or inhibit the secretion of pituitary hormones.