question: Why does salt makes us thirsty?
comment: The bit of basic physics to be known here is the concept of the "osmotic gradient." Simply put, water will flow towards high concentrations of solute (in this case, salt). If there's a lot of salt in your blood -- say, after eating a lot of salty food -- the water in your cells will flow out, into the space outside the cells, to try to bring the concentrations into balance. Your body senses this outflow of water and causes you to feel thirsty, so you drink more water, because there's less in your cells.
passages: In addition, there are visceral osmoreceptors. These project to the area postrema and nucleus tractus solitarii in the brain.
  
  Section::::Detection.:Salt craving.
  
  Because sodium is also lost from the plasma in hypovolemia, the body's need for salt proportionately increases in addition to thirst in such cases. This is also a result of the renin-angiotensin system activation.
  
  Section::::Detection.:Elderly.
   Section::::Function of sodium ions.
  
  Sodium is the primary cation (positive ion) in extracellular fluids in animals and humans. These fluids, such as blood plasma and extracellular fluids in other tissues, bathe cells and carry out transport functions for nutrients and wastes. Sodium is also the principal cation in seawater, although the concentration there is about 3.8 times what it is normally in extracellular body fluids.
  
  Section::::Function of sodium ions.:Human water and salt balance.
   Salt has long held an important place in religion and culture. At the time of Brahmanic sacrifices, in Hittite rituals and during festivals held by Semites and Greeks at the time of the new moon, salt was thrown into a fire where it produced crackling noises. The ancient Egyptians, Greeks and Romans invoked their gods with offerings of salt and water and some people think this to be the origin of Holy Water in the Christian faith. In Aztec mythology, Huixtocihuatl was a fertility goddess who presided over salt and salt water.
   Osmoreception is the body's sensation of thirst. When the amount of water in one's body falls below a certain threshold, the concentration of osmolytes (e.g. salt) increase in one's blood. Osmoreceptors, or sensory receptors in the hypothalamus, detect these changes in osmotic concentration. These signals are then transferred to neural signals of thirst.
  
  Section::::Loss of sensation.
   Clusters of cells (osmoreceptors) in the organum vasculosum of the lamina terminalis (OVLT) and subfornical organ (SFO), which lie outside of the blood brain barrier can detect the concentration of blood plasma and the presence of angiotensin II in the blood. They can then activate the median preoptic nucleus which initiates water seeking and ingestive behavior. Destruction of this part of the hypothalamus in humans and other animals results in partial or total loss of desire to drink even with extremely high salt concentration in the extracellular fluids.
   Circulating water and solutes in the body maintain blood pressure in the blood, as well as other functions such as regulation of body temperature. When salt is ingested, it is dissolved in the blood as two separate ions – Na and Cl. The water potential in blood will decrease due to the increase solutes, and blood osmotic pressure will increase. While the kidney reacts to excrete excess sodium and chloride in the body, water retention causes blood pressure to increase.
  
  Section::::Effect of salt on blood pressure.:DASH-Sodium study.
   b. The blood supply system to the gland is set in countercurrent exchange loop mechanism for keeping the high concentration of salt in the gland's blood, so that it doesn't leave back to the blood system.
  
  The glands remove the salt efficiently and thus allow the birds to drink the salty water from their environment while they are hundreds of miles away from land.
  
  Section::::Countercurrent exchange in industry and scientific research.
   Section::::Detection.:Decreased volume.:Renin-angiotensin system.
   The human body has evolved to balance salt intake with need through means such as the renin–angiotensin system. In humans, salt has important biological functions. Relevant to risk of cardiovascular disease, salt is highly involved with the maintenance of body fluid volume, including osmotic balance in the blood, extracellular and intracellular fluids, and resting membrane potential.
   Thirst
  
  Thirst is the craving for potable 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 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.
   BULLET::::- In Shinto, salt ritually purifies locations and people and piles of salt are placed in dishes by the entrance of businesses to ward off evil and attract patrons.
  
  BULLET::::- In the Old Testament thirty-five verses mention salt, some examples are:
  
  BULLET::::- In the New Testament, six verses mention salt, examples include:
  
  BULLET::::- In Catholicism:
   Since only some plants need sodium and those in small quantities, a completely plant-based diet will generally be very low in sodium. This requires some herbivores to obtain their sodium from salt licks and other mineral sources. The animal need for sodium is probably the reason for the highly conserved ability to taste the sodium ion as "salty." Receptors for the pure salty taste respond best to sodium, otherwise only to a few other small monovalent cations (Li, NH, and somewhat to K). Calcium ion (Ca) also tastes salty and sometimes bitter to some people but, like potassium, can trigger other tastes.
   Section::::Salt in religion.
  
  One of the reasons that this superstition has been so enduring and widespread is that salt has long held an important place in religions of many cultures.
  
  BULLET::::- In Brahmanic sacrifices and during festivals held by Semites as well the Greeks at the time of the new moon, salt was thrown into fire to make crackling noises.
  
  BULLET::::- Ancient Egyptians, Greeks, and Romans invoked gods with salt offerings. Some people think this to be the origin of Holy Water in Christianity.
  
  BULLET::::- In Aztec mythology, Huixtocihuatl was a fertility goddess who presided over salt and salt water.
   Sodium ions play a diverse and important role in many physiological processes, acting to regulate blood volume, blood pressure, osmotic equilibrium and pH.
  
  Section::::Sodium distribution in species.:Plants.
   The well known effect of sodium on blood pressure can be explained by comparing blood to a solution with its salinity changed by ingested salt. Artery walls are analogous to a selectively permeable membrane, and they allow solutes, including sodium and chloride, to pass through (or not), depending on osmosis.
   In ancient Rome, salt on the table was a mark of a rich patron; those who sat nearer the host were "above the salt", and those less favored were "below the salt". The Roman historian Pliny the Elder stated as an aside in his Natural History's discussion of sea water, that "[I]n Rome ... the soldier's pay was originally salt and the word 'salary' derives from it ..."
   Section::::Biological role.
   During India's independence movement, Mohandas Gandhi organized the Salt Satyagraha protest to demonstrate against the British salt tax.
  
  Section::::History.:Cities and wars.:English "-wich towns".
   Section::::Detection.:Decreased volume.
   BULLET::::- "Wanka da garri ba ya maganin yunwa." "Taking a bath with garri is not going to cure hunger."
  
  Section::::Process.
   In the Old Testament, in , "David struck down 18,000 Edomites in the Valley of Salt." In addition, "tells the story of the prophet Elisha pouring salt onto Jericho's water springs."
   Section::::Detection.:Decreased volume.:Others.
  
  BULLET::::- Arterial baroreceptors sense a decreased arterial pressure, and signals to the central nervous system in the area postrema and nucleus tractus solitarii.
  
  BULLET::::- Cardiopulmonary receptors sense a decreased blood volume, and signal to area postrema and nucleus tractus solitarii as well.
  
  Section::::Detection.:Cellular dehydration and osmoreceptor stimulation.
   Salt is essential for life in general, and saltiness is one of the basic human tastes. Salt is one of the oldest and most ubiquitous food seasonings, and salting is an important method of food preservation.
   Section::::Hypertension and cardiovascular disease.:Debate on the link between salt intake and cardiovascular disease.
   BULLET::::- Potassium, a very common electrolyte (heart and nerve health). With sodium, potassium is involved in maintaining normal water balance, osmotic equilibrium, and acid-base balance. In addition to calcium, it is important in the regulation of neuromuscular activity. Food sources include bananas, avocados, vegetables, potatoes, legumes, fish, and mushrooms.
  
  BULLET::::- Sodium, a very common electrolyte; not generally found in dietary supplements, despite being needed in large quantities, because the ion is very common in food: typically as sodium chloride, or common salt.
  
  Section::::Nutrients.:Minerals.:Trace minerals.
  