regulation of plasma osmolarity (12) Flashcards
what is the average total in gain of water?
2500 mL/day
what is the greatest source of water loss per day? how much is this?
urine 1500 mL/day
what are the unregulated water losses from the body?
feces
skin/sweat
exhaled air
when the U/P osmolarity =1 tell me about the osmolarity of the urine and ECF
the urine is isotonic and ECF osmolarity is also isotonic
when the U/P osmolarity >1 tell me about the osmolarity of the urine and ECF
the urine is hypertonic and ECF osmolarity is also hypertonic
when the U/P osmolarity < 1 tell me about the osmolarity of the urine and ECF
the urine is hypotonic and the ECF osmolarity is also hypotonic
what is the typical osmolar excretion of solutes in the urine per day?
600 mOsmoles/day in the urine
how high can the kidney increase the urine osmolarity to? how low?
can increase the osmolarity to 1200 mOsm/L or decrease osmolarity to 30 mOsm/L
define “free water”
water that is not osmotically obligated to remain in the tubular fluid due to presence of solutes
define “free water clearance”
the rate/time dependent ability of the kidney to take water from the tubular fluid and put in the plasma (or opposite)
high or low plasma osmolarity will cause ADH releasE?
high plasma osmolarity
what limits the positive & negative free water clearance?
the magnitude of solute consumed
what will consuming a diet low in solute do to the free water clearance
increase the negative free water clearance and decrease the positive free water clearance
describe the osmolarity of the tubular fluid in the proximal tubular
iso-osmotic
describe the osmolarity of the tubular fluid in the loop of henle
hypo-osmotic
describe what “antidiuresis” means
refers to restricted water intake (hydropenia) when the kidneys maximally concentrate the urine and excrete a minimal volume of urine because of increase absorption of water in excess of solutes
describe what “diuresis” means
refers to ingestion of excess water when kidneys maximally dilute the urine & excrete a large volume of urine because absorption of water in excess of solutes does not occur
describe the osmolarity of the fluid entering the distal convoluted tubule
relatively hypo-osmotic
what area and factors determine the osmolarity of urine?
depends on whether or not water is reabsorbed in the initial and cortical collecting tubules (ICT and CCT) and the outer and inner medullary collecting ducts (OMCD and IMCD)
ADH/AVP acts on these nephron segments
where is antidiuretic hormone synthesized?
paraventricular and supraoptic nuclei of the hypothalamus
what is the half-life of ADH and why is this important?
18 minutes- this is important because you want to be able to quickly shut this off when the volume/osmolarity returns to normal. Gives you the timliness of the kidneys to act quickly
what is the function of ADH?
increase the water permeability of the principal cells of the outer & inner medullary collecting tubules & ducts
tell me about the binding of ADH/AVP in the distal tubule
binds to V2 receptors in the basolateral membrane of “principal cells” where present in the cells of the initial collecting tubule to the end of the collecting duct
these receptors are receptors are G protein coupled and stimulate adenyl cyclase to produce camp which then activates PKA
true or false
ADH is able to act on the aquaporins located on the basalateral and the apical membrane
ONLY the apical membrane
the channels on the basolateral membrane are NOT regulated
what two areas in the hypothalamus have the osmoreceptors
organum vasculosum of the lamina terminalis (OVLT) and the subfornical organ (SFO)
explain how osmolarity affects the osmoreceptors to act to increase the release of ADH
An increase in osmolarity opens the mechano-sensitve cation channels causing depolarization of the membrane potential which will increase the frequency of APs traveling to ADH/AVP synthesizing & secreting neurons in the hypothalamus
