Thirst
[Ref:WG22:p240-242; KB2:p3-4]
Stimulus for water intake
- Hypertonicity
- Hypovolaemia
- Hypotension
- Angiotensin II
- Others
* Social factors
* Psychological factors
* Dryness of the pharyngeal mucosal membrane
- Increased effective osmotic pressure of plasma
- Decreases in ECF volume
* Via angiotensin II
- Psychological factors
- Social factors
- Dryness of the pharyngeal mucous membrane
Osmolality
Increased osmotic pressure
--> Acts on osmoreceptors
* Located in anterior hypothalamus
ECF volume
Decreased ECF volume
--> Increase renin secretion
--> Increase angiotensin II production
Angiotensin acts on subfornical organ (SFO)
--> Increase thirst
Some evidence that angiotensin might also act on organum vasculosum of the lamina terminalis (OVLT)
Others
- Baroreceptor in heart and blood vessels are also involved.
- Lesions of the anterior communicating artery can obtund thirst because branches of this artery supplies the hypothalamic area concerned with thirst