All Topics  
Thirst

 
Thirst

 
   Email Print
   Bookmark   Link
 

 

Thirst
 
 
  Topics Thirst Topic Home

Thirst is the craving for liquids, resulting in the basic instinct
Instinct

Instinct is the inherent disposition of a life organism toward a particular behavior. The fixed action patterns are unlearned and inherited. The stimuli can can be variable due to imprinting in a sensitive period or also genetically fixed....
 of humans or animals to drink
Drink

A drink, or beverage, is a liquid specifically prepared for human consumption. In addition to basic needs, beverages form part of the culture of human society....
. It is an essential mechanism involved in fluid balance
Fluid balance

Fluid balance is the concept of human homeostasis that the amount of fluid lost from the body is equal to the amount of fluid taken in. Euvolemia is the state of normal body fluid volume....
. It arises from a lack of fluids and/or an increase in the concentration of certain osmolites such as salt
Salt

A salt, in chemistry, is defined as the product formed from the neutralisation reaction of acids and base . Salts are ionic compounds composed of cations and anions so that the product is electrically electric charge ....
.






Discussion
Ask a question about 'Thirst'
Start a new discussion about 'Thirst'
Answer questions from other users
Full Discussion Forum



Encyclopedia


William Adolphe Bouguereau (1825 1905) Thirst (1886)
Thirst is the craving for liquids, resulting in the basic instinct
Instinct

Instinct is the inherent disposition of a life organism toward a particular behavior. The fixed action patterns are unlearned and inherited. The stimuli can can be variable due to imprinting in a sensitive period or also genetically fixed....
 of humans or animals to drink
Drink

A drink, or beverage, is a liquid specifically prepared for human consumption. In addition to basic needs, beverages form part of the culture of human society....
. It is an essential mechanism involved in fluid balance
Fluid balance

Fluid balance is the concept of human homeostasis that the amount of fluid lost from the body is equal to the amount of fluid taken in. Euvolemia is the state of normal body fluid volume....
. It arises from a lack of fluids and/or an increase in the concentration of certain osmolites such as salt
Salt

A salt, in chemistry, is defined as the product formed from the neutralisation reaction of acids and base . Salts are ionic compounds composed of cations and anions so that the product is electrically electric charge ....
. If the water volume of the body falls below a certain threshold, or the osmolite concentration becomes too high, the brain
Brain

The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as cnidarian and echinoderm have a decentralized nervous system without a brain, while sponges lack any nervous system at all....
 signals thirst.

Continuous dehydration
Dehydration

Dehydration is the removal of water from an object. In Physiology terms, it entails a relative deficiency of water molecules in relation to other dissolved solutes....
 can cause myriad problems, but is most often associated with neurological problems such as seizures, and renal
Kidney

The kidneys are Organ that have numerous biological roles. Their primary role is to maintain the homeostasis balance of bodily fluids by filtering and secreting Metabolomics#Metabolitess and minerals from the blood and excreting them, along with water , as urine....
 problems. Excessive thirst, known as polydipsia
Polydipsia

Polydipsia is a medical symptom in which the patient displays excessive thirst. The word derives from the Greek language p???d???a, which is derived from p???? + d??a ....
, along with excessive urination, known as polyuria
Polyuria

In medicine, polyuria is a condition characterized by the passage of large volumes of urine .Polyuria often appears in conjunction with polydipsia , though it is possible to have one without the other, and the latter may be a cause or an effect....
, may be an indication of diabetes.

There are receptors and other systems in the body that detect a decreased volume or an increased osmolite concentration. They signal to the central nervous system
Central nervous system

The central nervous system is the part of the nervous system that functions to coordinate the activity of all parts of the bodies of multicellular organisms....
, where central processing succeeds. Some sources therefore distinguish "extracellular thirst" from "intracellular thirst", where extracellular thirst is thirst generated by decreased volume and intracellular thirst is thirst generated by increased osmolite concentration. Nevertheless, the craving itself is something generated from central processing in the brain, no matter how it is detected.

Detection

There are many different receptors for sensing decreased volume or an increased osmolite concentration.

Decreased volume

Further reading: Hypovolemia
Hypovolemia

In physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma. Volumetric thirst can be caused by a number of things including bleeding and diarrhea....
  • Renin-angiotensin system
Hypovolemia leads to activation of the renin angiotensin system (RAS) and a decrease in atrial natriuretic peptide
Atrial natriuretic peptide

Atrial natriuretic peptide , atrial natriuretic factor , atrial natriuretic hormone , or atriopeptin, is a weak vasodilator, and a protein hormone secreted by heart muscle cells....
. These mechanisms, along their other functions, contribute to elicit thirst, by affecting the subfornical organ
Subfornical organ

The subfornical organ, situated on the ventral surface of the Fornix of brain, at the foramen of Monro, is one of the circumventricular organs of the brain....
.. For instance, angiotensin II, activated in RAS, is a powerful dipsogen
Dipsogen

A dipsogen is an agent that causes thirst. ...
 (ie it stimulates thirst) which acts via the subfornical organ.

  • Other
    • Arterial baroreceptors sense a decreased arterial pressure, and signals to the central nervous system
      Central nervous system

      The central nervous system is the part of the nervous system that functions to coordinate the activity of all parts of the bodies of multicellular organisms....
       in the area postrema
      Area postrema

      The area postrema is a part of the brain that controls vomiting. It was discovered in 1953 by Utah Pharmacologists Herbert L. Borison and S. C. Wang ....
       and nucleus tractus solitarius.
    • Cardiopulmonary receptor
      Cardiopulmonary receptor

      Sorry, no overview for this topic
      s sense a decreased blood volume, and signal to area postrema
      Area postrema

      The area postrema is a part of the brain that controls vomiting. It was discovered in 1953 by Utah Pharmacologists Herbert L. Borison and S. C. Wang ....
       and nucleus tractus solitarius as well.


Increased osmolite concentration

An increase in osmotic pressure
Osmotic pressure

Osmotic pressure is the Fluid_statics#Hydrostatic_pressure produced by a difference in concentration between solutions on the two sides of a surface such as a differentially permeable membrane....
, e.g. after eating a salty meal activates osmoreceptor
Osmoreceptor

An osmoreceptor is a sensory receptor primarily found in the hypothalamus of most homeothermic organisms that detects changes in osmotic pressure....
s. There are osmoreceptors already in the central nervous system
Central nervous system

The central nervous system is the part of the nervous system that functions to coordinate the activity of all parts of the bodies of multicellular organisms....
, more specifically in the hypothalamus
Hypothalamus

The hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland ....
, notably in two circumventricular organs that lack an effective blood-brain barrier
Blood-brain barrier

The blood-brain barrier is a metabolic or cellular structure in the central nervous system that restricts the passage of various chemical substances and microscopic objects between the bloodstream and the neural tissue itself, while still allowing the passage of substances essential to metabolism function ....
, the organum vasculosum of the lamina terminalis
Organum vasculosum of the lamina terminalis

The organum vasculosum of the lamina terminalis is one of the circumventricular organs of the brain . Other circumventricular organs are the subfornical organ and the area postrema in the brainstem....
 (OVLT) and the subfornical organ
Subfornical organ

The subfornical organ, situated on the ventral surface of the Fornix of brain, at the foramen of Monro, is one of the circumventricular organs of the brain....
 (SFO). However, although located in the same parts of the brain, these osmoreceptors that evoke thirst are distinct from the neighbouring osmoreceptors in the OVLT and SFO that evoke arginine vasopressin release to decrease fluid output.

In addition, there are visceral osmoreceptors. These project to the area postrema
Area postrema

The area postrema is a part of the brain that controls vomiting. It was discovered in 1953 by Utah Pharmacologists Herbert L. Borison and S. C. Wang ....
 and nucleus tractus solitarius in the brain.

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.

Senior citizens

For adults over age 50, the body’s thirst
Thirst

Thirst is the craving for liquids, resulting in the basic instinct of humans or animals to drink. It is an essential mechanism involved in fluid balance....
 sensation diminishes and continues diminishing with age, causing many to suffer symptoms of dehydration
Dehydration

Dehydration is the removal of water from an object. In Physiology terms, it entails a relative deficiency of water molecules in relation to other dissolved solutes....
.

Central processing

The area postrema
Area postrema

The area postrema is a part of the brain that controls vomiting. It was discovered in 1953 by Utah Pharmacologists Herbert L. Borison and S. C. Wang ....
 and nucleus tractus solitarius signal, by 5-HT, to lateral parabrachial nucleus
Lateral parabrachial nucleus

The lateral parabrachial nucleus induces thirst by stimulating the median preoptic nucleus.It gets its name from its location relative to the superior cerebellar peduncles, which is also known as the "brachia conjunctiva"....
, which in turn signal to median preoptic nucleus. In addition, the area postrema and nucleus tractus solitarius also signal directly to subfornical organ.

Thus, the median preoptic nucleus and subfornical organ receive signals of both decreased volume and increased osmolite concentration. They signal to higher integrative centers, where ultimately the conscious craving arises. However, the true neuroscience
Neuroscience

Neuroscience is a field devoted to the scientific study of the nervous system. The Society for Neuroscience was founded in 1969, but the study of the brain started a long time ago....
 of this conscious craving is not fully clear.

In addition to thirst, the organum vasculosum of the lamina terminalis
Organum vasculosum of the lamina terminalis

The organum vasculosum of the lamina terminalis is one of the circumventricular organs of the brain . Other circumventricular organs are the subfornical organ and the area postrema in the brainstem....
 and the subfornical organ
Subfornical organ

The subfornical organ, situated on the ventral surface of the Fornix of brain, at the foramen of Monro, is one of the circumventricular organs of the brain....
 contribute to fluid balance
Fluid balance

Fluid balance is the concept of human homeostasis that the amount of fluid lost from the body is equal to the amount of fluid taken in. Euvolemia is the state of normal body fluid volume....
 by vasopressin
Vasopressin

Arginine vasopressin , also known as vasopressin, argipressin or antidiuretic hormone , is a hormone found in most mammals, including humans....
 release.

See also

  • Hunger
    Hunger

    Hunger is a feeling experienced when one has a desire to eat. The often unpleasant feeling originates in the hypothalamus and is released through receptors in the liver....
  • Dehydration
    Dehydration

    Dehydration is the removal of water from an object. In Physiology terms, it entails a relative deficiency of water molecules in relation to other dissolved solutes....