Hypothalamus Health Dictionary

A region of the brain, roughly the size of a cherry, situated behind the eyes and the thalamus.

The hypothalamus controls the sympathetic nervous system (part of the autonomic nervous system). In response to sudden alarm or excitement, signals are sent from higher regions of the brain to the hypothalamus, initiating sympathetic nervous system activity. This causes a faster heartbeat, widening of the pupils, an increase in breathing rate and blood flow to muscles.

Other nerve cells in the hypothalamus are concerned with the control of body temperature, thirst, and appetite for food. The hypothalamus is also involved in regulating sleep, motivating sexual behaviour, and determining mood and emotions. It indirectly controls many endocrine glands through its influence on the pituitary gland.

Disorders of the hypothalamus are usually due to an intracerebral haemorrhage or a pituitary tumour. They have diverse effects, ranging from hormonal disorders to disturbances in temperature regulation, and increased or decreased need for food and sleep.

A part of the diencephalon of the brain, it is a major actor in the limbic system. This is a functional, not anatomic, system in the brain that influences and is influenced by emotions. Call the limbic system an ad hoc committee that decides how things are going today, based on past, present, potential, and myriad informational inputs from the somatic body. The hypothalamus gathers the data and sets the levels of the pituitary thermostat. The pituitary does what the hypothalamus tells it to do, and our whole chemical nervous system responds to the pituitary, which responds to the hypothalamus, which, along with the rest of the limbic system, decides the kind of day we need to get ready for. And to think that some doctors used to (and still) scoff at a “psychosomatic disorder.”

That part of the fore-brain situated beneath and linked with the THALAMUS on each side and forming the ?oor of the third ventricle (see BRAIN). Also linked to the PITUITARY GLAND beneath it, the hypothalamus contains collections of nerve cells believed to form the controlling centres of (1) the sympathetic and (2) the parasympathetic nervous systems (see under NERVOUS SYSTEM). The hypothalamus is the nervous centre for primitive physical and emotional behaviour. It contains nerve centres for the regulation of certain vital processes: the metabolism of fat, carbohydrate and water; sleep; body temperature and sexual functions.

n. the region of the forebrain in the floor of the third ventricle, linked with the thalamus above and the *pituitary gland below (see brain). It contains several important centres controlling body temperature, thirst, hunger, and eating, water balance, and sexual function. It is also closely connected with emotional activity and sleep and functions as a centre for the integration of hormonal and autonomic nervous activity through its control of the pituitary secretions (see neuroendocrine system; pituitary gland). —hypothalamic adj.