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