The central controller for water balance is
the hypothalamus but there is no single anatomically
defined ‘center’ which is solely responsible for producing
an integrated response to changes in water balance. There are
numerous pathways interconnecting the various centers or areas
in the hypothalamus. The osmoreceptors are located in the area
known as the AV3V (anteroventral 3rd ventricle). Lesions in the
AV3V region in rats cause acute adipsia.
The thirst centre is located in the lateral
hypothalamus. It receives input from osmoreceptors in the AV3V
region and from the subfornical organ and the organum vasculosum
of the lamina terminalis (OVLT) which are sites for angiotensin
II action. The OVLT is in the AV3V region.
ADH is formed predominantly in the neurones of the supraoptic
and paraventricular nuclei. These nuclei receive input from the
osmoreceptors and also from ascending adrenergic pathways from
the low and the high pressure baroreceptors. Aquaporin 4 has
recently been identified in cells in the hypothalamus
particularly in the paraventricular and supraoptic nuclei.
The key parts of the hypothalamus involved in water balance
OVLT & SFO (respond to angiotensin II)
Supraoptic & paraventricular nuclei (for ADH
All material © Copyright - Kerry Brandis, 2001