Water Balance (Thirst)

OVLT organum vasculosum laminae terminalis and subfornical organ (SFO)

areas important for detecting osmotic pressure and salt concetration

aldosterone

cause kidneys, salivary glands and sweat glands to retain salt

angiotensin II

constricts the blood vessels and compensates for the drop in blood pressure that resulted from release of renin when the blood volume drops

Supraopic nuleus and paraventricular nucleus (PVN)

control rate at which the posterior pituitary relaeses vasopressin

lateral proptic area

controls drinking

osmotic thirst

eating salty foods and losing fulid causes this

antidiuetic hormone (ADH)

enables the kidneys to reabsorb water from urine and therfore make the urine more concentrated; vasopressin is also known as this

set point

fixed concentration of solutes

area around 3rd ventricle

has the leakies blood-brain barriear-->helps monitor contents of blood

osmotic thirst

helps restore the normal state

vasopression

raises blood pressure by constricting the blood vessels; increased pressure helps compensate for th decreased volume

renin

splits a portion off angiotensignogen, a large protein in the blood to form angiotensin I

osmotic pressure

tendency of water to flow across a semipermeable membrane from teh area of low solute concetration to the area aof a higher concentration; occurs when solutes are more concenrated on on eside of the membrane than on the other--when sodium ions spread through the blood and extracelluar fud but do not creoos the membranes into cells (result = water drawn from cells into extracellular matrix)

hypovolemic

thirst based on low volume; need to restore lost salts not just water

hypovelemic thirst

thrist caused by bleeding or sweatig

When to stop drinking

water must be absorbed through the digestive system and then pumped through the blood to the brain-->body monitors swallowing and detects distension of stomach and upper part of the small intestine