The organum vasculosum of the lamina terminalis (OVLT) (or supraoptic crest) is one of the circumventricular organs

Circumventricular organs

Circumventricular organs are so named because they are positioned at distinct sites around the margin of the ventricular system of the brain.They are among the few sites in the brain which have an incomplete blood–brain barrier...

 of the brain. Other circumventricular organs are the subfornical organ

Subfornical organ

The subfornical organ, situated on the ventral surface of the fornix, at the interventricular foramina , is one of the circumventricular organs of the brain.-Relations with other circumventricular organs:...

 (SFO) and the area postrema

Area postrema

The area postrema is a medullary structure in the brain that controls vomiting. Its privileged location in the brain also allows the area postrema to play a vital role in the control of autonomic functions by the central nervous system.-Anatomy:...

 in the brainstem.

AV3V region

The OVLT and the SFO are both strongly interconnected with the median preoptic nucleus of the hypothalamus

Hypothalamus

The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...

 (the nucleus medianus), and together these three structures comprise the so called "AV3V" region - the region anterior and ventral to the third ventricle. The AV3V region is very important in the regulation of fluid and electrolyte balance by controlling thirst, sodium excretion, blood volume regulation, and vasopressin secretion.

Function

The OVLT is outside the blood brain barrier, and so neurons in this region can respond to factors that are present in the systemic circulation.

Some neurons in the OVLT are osmoreceptor

Osmoreceptor

An osmoreceptor is a sensory receptor primarily found in the hypothalamus of most homeothermic organisms that detects changes in osmotic pressure. Osmoreceptors can be found in several structures, including the organum vasculosum of the lamina terminalis and the subfornical organ...

s, being sensitive to the osmotic pressure

Osmotic pressure

Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane....

 of the blood. These neurons project to the supraoptic nucleus

Supraoptic nucleus

The supraoptic nucleus is a nucleus of magnocellular neurosecretory cells in the hypothalamus of the mammalian brain. The nucleus is situated at the base of the brain, adjacent to the optic chiasm...

 and paraventricular nucleus

Paraventricular nucleus

The paraventricular nucleus is a neuronal nucleus in the hypothalamus. It contains multiple subpopulations of neurons that are activated by a variety of stressful and/or physiological changes. Many PVN neurons project directly to the posterior pituitary where they release oxytocin or vasopressin...

 to regulate the activity of vasopressin

Vasopressin

Arginine vasopressin , also known as vasopressin, argipressin or antidiuretic hormone , is a neurohypophysial hormone found in most mammals, including humans. Vasopressin is a peptide hormone that controls the reabsorption of molecules in the tubules of the kidneys by affecting the tissue's...

-secreting neurons. These neurons also project to the nucleus medianus (also called the medial preoptic nucleus) which is involved in controlling thirst

Thirst

Thirst is the craving for fluids, resulting in the basic instinct of animals to drink. It is an essential mechanism involved in fluid balance. It arises from a lack of fluids and/or an increase in the concentration of certain osmolites, such as salt...

.

External links

• http://www.sci.uidaho.edu/med532/lamina.htm