The hypothalamus and autonomic regulation: an overview

The hypothalamus plays a key role in regulating autonomic function, usually as part of more generalized, often quite stereotyped, behavioural responses triggered by internal challenges (e.g., a change in body temperature or blood glucose levels) or external threats (e.g., the sight, sound or odour of a predator). Neurons within hypothalamic nuclei (especially the paraventricular nucleus, dorsomedial hypothalamus and perifornical area) make direct and indirect connections with sympathetic and parasympathetic preganglionic neurons and, in turn, receive inputs from a wide variety of sources, including (1) visceral and pain receptors, (2) receptors in circumventricular organs signalling changes in blood levels of circulating substances, and (3) inputs from the external environment, such as inputs signalling changes in temperature, light, and odour. Hypothalamic nuclei, especially the paraventricular nucleus and dorsomedial hypothalamus, are believed to generate the marked increases in sympathetic activity associated with disorders, such as neurogenic hypertension, severe heart failure and panic disorder.