renal regulation of water and acidbase balance Flashcards
what is osmotic pressure dependent on
total number of solute particles
how can we calculate osmolarity
concentration x no. of dissociated particles
osm/l
what are some form of unregulated water loss
sweat faeces
vomit
water evaporation from skin
what is regulated water loss
renal regulation - urine production
what is positive water balance
happens when there is high water intake
causes increase in ecf vol
decreased na+ and decreased osmolarity
.. therefore kidneys produce hyposmotic (dilute) urine production
what is negative water balance
happens when low water intake
decreased ecf vol but increased na+ and osmolarity
kidneys produce hyperosmotic urine and triggers thirst
where is 67% of water reabsorbed in kidneys
proximal convoluted tubule
what % of water is reabsorbed at thin descending limb
15%
no na or cl reabsorbed
is any water reabsorbed at ascending limb
no only na and cl reabsorbed
why does medullary interstitium need to be hyperosmotic
for water reabsorption to occur from loop of henle and collecting ducts
what are vasa recta
series of blood capillaries that surround your nephron mainly in medullary region
how is urea transported out collecting duct into medullary interstitium
via uta3 and uta1 transporters
where can urea travel to after leaving the collecting duct
into vasa recta via utb1 transporter or into thin ascending limb via uta2 transporter
what is the reason behind why urea increases interstitium osmolarity
urine concentration occurs
urea excretion requires less water
what is vassopressins role in urea
boosts uta1 and uta3 numbers and increases permeability of collecting duct for urea
what is the main function of adh/vasopressin
promote water reabsorption from collecting duct
where is vasopressin/adh produced
hypothalamus - neurons in supraoptic and praventricular nuclei
what are some stimulatory factors that influence adh production and release
increase in plasma osmolarity hypovolemia decrease in blood pressure nausea angiotensin 2 nicotine
what are some inhibitory factors influencing adh production and release
decrease in plasma osmolarity hypervolemia increase in blood pressure ethanol atrial natriuretic peptide
what % change is required for detection by baroreceptors for adh release/inhibition
5-10%
what is the mechanism of adh
adh binds to v2 receptor on basolateral membrane of collecting duct
activates g coupled protein mediated signalling cascade
activates protein kinase A
and increases secretion of aqp2 which are inserted into apical membrane
what is diuresis
increased dilute urine excretion
what is antidiuresis
concentrated urine in low volume excretion
treatment for syndrome of inappropriate adh secretion (siadh)
non-peptide inhibitor of adh receptor - conivaptan and tolvaptan
what is the treatment of nephrogenic diabetes insipidus
thiazide diuretics and nsaids
what is the role of kidneys in acidbase balance
secretion and excretion of h+
reabsorption of hco3-
production of new hco3-
what is the neutral ecf hco3-
~ 350mEq or 24mEq/L
what % of bicarbonate ions are reabsorbed by kidneys
almost 100%
around 80% in pct
10% in thick ascending limb
how are h+ ions reabsorbed in pct
- via na+h+ antiporter
2. h+ atpase pump
how are bicarbonate ions reabsorbed into blood
via na+hco3- symporter
what are the 2 different cells present in dct and collecting duct
alpha intercalated cell
beta intercalated cell
what is role of alpha intercalated cell
hco3- reabsorption and h+ secretion
what is the role of beta intercalated cells
hco3- secretion and h+ reabsorption
how are new bicarbonate ions produced
in proximal convoluted tubule glutamine is converted into 2 molecules of ammonia and 1 divalent ion which gives rise to 2 hco3- ions which are reabsorbed
ammonia re-enters blood circulation reaches liver and gets converted into one urea ion and one proton ion
THEREFORE ammonia must be excreted from body via na+h+ antiporter and becoming ammonia gas and binding with proton ion into tubular fluid
how are bicarbonate ions produced in dct and collecting duct
alpha intercalated cells
proton ion is neutralised with a phosphate ion
hco3- is gained
travels into blood via cl-hco3- antiporter
what are the characteristics of metabolic acidosis
low hco3-
low ph
what is the compensatory response to metabolic acidosis
increased ventilation
increased hco3- reabsorption and production
what are the characteristics of metabolic alkalosis
high hco3- and high ph
what is the compensatory response to metabolic alkalosis
decreased ventilation
increased hco3- excretion
what is respiratory acidosis
high pco2
low ph
what is the compensatory response to respiratory acidosis
acute - intracellular buffering
chronic - increase in hco3- reabsorption and production
what is respiratory alkalosis
low pco2 and high ph
what is the compensatory response to respiratory alkalosis
acute - intracellular buffering
chronic - decrease in hco3- reabsorption and production
