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Components of the neural circuitry controlling fluid balance. The circuitry is shown in a stylized sagittal section through the rat brain. Information from
baroreceptors in the circulatory system and from sensory receptors in the mouth, throat, and viscera is conveyed to the nucleus of the solitary tract and
neighboring structures in the caudal brain stem through the glossopharyngeal (IX) and vagal (X) nerves (right side). The hormone angiotensin II (ANG II)
provides the brain with an additional signal concerning low blood volume (left side). Circulating angiotensin II is sensed by receptors in the subfornical
organ (SFO); SFO neurons project to and release angiotensin II in the median preoptic area (MePO), paraventricular nucleus of the hypothalamus (PVN),
vascular organ of the lamina terminalis (OVLT), and adjacent lateral hypothalamic area (LHA). High arterial pressure is detected by baroreceptors that
Source: Homeostasis, Motivation, and Addictive States, Principles of Neural Science, Fifth Editon
project to the caudal brain stem; when arterial pressure is too high, drinking is suppressed by an inhibitory input to the median preoptic area from the
Citation:
Kandel
JH,
TM, is
Siegelbaum
Hudspeth
of Neural
Fifth Editon;
2012
Available
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paraventricular nucleus of the hypothalamus. The latter nucleus is positioned to integrate inputs concerning both blood volume and osmolality and is
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believed to play
a key role
in triggering
drinking.
Neurosecretory
cells in this nucleus (and in the supraoptic nucleus) trigger release of vasopressin from
the neural lobe (NL) of the pituitary, thus decreasing urinary output. Input to the paraventricular nucleus from the suprachiasmatic nucleus (SCN) brings