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William-Adolphe Bouguereau's Thirst (1886)

Thirst is the basihgdj[instinct]] of humans or animals to drink. It arises from a lack of fluids and/or an increase in the concentration of certain osmolites such as salt. If the water volume of the body falls below a certain threshold, or the osmolite concentration becomes too high, the brain signals thirst. The osmolite concentration in the blood is measured with specialized sensors in the hypothalamus, notably in two circumventricular organs that lack an effective blood-brain barrier, the organum vasculosum of the lamina terminalis and the subfornical organ. These areas project to the supraoptic nucleus and paraventricular nucleus, which contain neurons that secrete the antidiuretic hormone, vasopressin, from their nerve endings in the posterior pituitary, but also project to other hypothalamic areas, including especially the median preoptic nucleus to trigger thirst. Continuous dehydration can cause myriad problems, but is most often associated with neurological problems such as seizures, and renal problems.

Excessive thirst, known as polydipsia, along with excessive urination, known as polyuria, may be an indication of diabetes. Angiotensin II is a hormone which is a powerful dipsogen (ie it stimulates thirst) which acts via the subfornical organ.

Is the thirst caused by a reduction in the volume of fluid found between cells. This can be caused by a number of things including bleeding, vomiting, diarrhea, sweating, and alcohol consumption.

A liquid rich in electrolytes is needed to replenish.

• Nomadic peoples of the sahara drink and carry blood as a beverage for their extracellular thirst.

Thirst triggered when fluid is drawn out if cells due to an increase in the concentration of salts and minerals outside of the cell. Caused by salty snacks etc.

Water is best to rid this thirst.

For optimal health, experts recommend that humans get 8-10 servings of about 8-ounces (approximately 2 litres) of water per day to maintain hydration. This figure does vary according to ambient temperature, movement and physical size. Being that water is essential to the general function of the human and all animal bodies, eight servings is widely regarded as the minimum for the body to function optimally. However, water can be obtained from many sources, such as foods and other beverages containing water. Getting enough water from your diet and staying hydrated is key to your overall health, including urinary tract and digestive tract health.

When getting your daily water intake, it's important to not rely heavily on caffeinated beverages, as they actually work as a diuretic. Further, moderate or excessive alcohol consumption can lead to dehydration, thus it's important to maintain hydration when drinking caffeinated and alcoholic beverages.

• M.J. McKinley and A.K. Johnson (2004). "The Physiological Regulation of Thirst and Fluid Intake". News in Physiological Sciences 19 (1): 1-6. Retrieved on 2006-06-02. 

• Hunger

• Dehydration