Renal L3 Flashcards
when considering the body fluid compartments( plasms, interstitial, intracellular) an intravenous infusion of an isotonic solution will result in an in increase in the volume of:
-all compartments
-plasma only
-interstitial compartment only
-plasma and interstitial compartments only
-intracellular compartment only
plasma and interstitial compartments only
is an isotonic solution good at rehydrating cells?
NO
stays in the ECF and does not move into the cells
What is the effect of water ingestion on the ICF, and ECF( plasma and interstitial fluid)?
Water is hypoosmotic
water rapidly equilibrates throughout ECF & ICF. Osmolarity decreases everywhere. Water is evenly distributed.
Rehydrates cells
what is another name for ADH?
vasopressin
what effect does alcohol have on ADH?
inhibits ADH-> can result in dehydration
what is the main role of ADH in the body?
water reabsorption in the kidney
water retention
water balance
where is ADH produced and stored?
the precursor to ADH (AVP) is made in the hypothalamus and stored in vesicles in the posterior pituitary
what is the trigger for ADH release?
osmoreceptors innervating the hypothalamus sense:
-increase in Na+ concentration
-Increase in osmolarity
e.g. from dehydration
-> signal send to the pituitary to release ADH into the bloodstream
what is the trigger for ADH release?
osmoreceptors innervating the hypothalamus sense:
-increase in Na+ concentration
-Increase in osmolarity
* also Blood Volume
e.g. from dehydration
-> signal send to the pituitary to release ADH into the bloodstream
where are osmoreceptors located?
hypothalamus
how do osmoreceptors work?
osmoreceptors have stretch-inhibited(shrink-activated) cation channels
when the cell shrinks due to the hypertonic stimulus cation( Na+) channels open
Na+ entering the cell triggers AP
increased osmolarity- increased firing rate of osmoreceptors
relationship between plasma osmolarity and plasma AVP/ADH lvl
Plasma AVP/ADH increases as osmolarity increases
what part of the tubule does the ADH act on?
last part of the convoluted distal tubule and the collecting duct
how does ADH cause water reabsorption?
ADH binds to the receptors on the basolateral side of the principal cells in the collecting duct.
This triggers a 2nd messenger pathway, causing vesicles inside the cell to merge and insert aquaporin-2 channels into the apical membrane.
Water can now move out of the filtrate through aquaporin-2 channels into the cells
the basolateral membrane is always relatively permeable to water, thus water can now move via osmosis back into the blood
This results in a small volume of concentrated urine being produced
what is the alternative way for ADH to be stimulated apart from Na+ concentration and osmolarity?
decrease in Blood pressure( 10-15%)
decreased in plasma volume
this is sensed by baroreceptors
stimulate ADH release
what is the main function of the renin-angiotensin-aldosterone system?
regulate BP by Na+ retention
regulate Na+ balance
what cells respond to the decrease in NaCl content?
macula densa cells in the distal convoluted tubule
how do macula densa cells respond to decrease in NaCl content?
by increasing prostaglandins
what cells release Renin?
Juxtaglomerular
what stimulates Renin release?
-low NaCl concentration in the distal tubule( sensed by Macula Densa cells)
-decreased perfusion pressure in the afferent arteriole( sensed by granular cells)
-increased sympathetic activity( via baroreflex)
i.e Low BP, BV, or NaCl content
renin-angiotensin system
where is aldosterone released from?
adrenal cortex
what is the action of aldosterone in the kidney?
Aldosterone acts on the principal cells of the distal tubule and collecting ducts to increase transcription of Na+/K+ ATPase pumps in the basolateral membrane thus increasing Na+ reabsorption and K+ excretion
Water reabsorption may also increase as long as ADH is also present!
-Na+ and water retention!!!
what is the effect of eating salty chips on plasma, ICF, and interstitial volume?
increased osmosis of water from intracellular fluid to interstitial fluid to plasma
increased Blood (plasma) Volume
what is the effect of eating salty chips on the body?
-increase in BV
-decrease in renin release
-increased atrial natriuretic peptide(ANP)
-reduced reabsorption of NaCl by the kidneys
-increased loss of water in urine by osmosis
all eventually lead to a decrease in BV
what are the effects of angiotensin 2?
- it is a potent vasoconstrictor, thus it decreases glomerular filtration by vasoconstricting the afferent arteriole
-it increases Na+ and water reabsorption in the proximal and distal convoluted tubules
-it stimulates the release of aldosterone from the adrenal cortex. Aldosterone acts on the collecting ducts to reabsorb more Na+ and Cl-
-stimulates thirst and salt intake, release of ADH
how do ACE inhibitors work?
inhibit ACE
reduce angiotensin 2 lvls
work by getting rid of Na+ and water
reduce BP and BV
helps with edema and heart expansion
in what situation would both ADH and renin-angiotensin systems be working together?
Hemorrhage- loss of Na+ AND water
why would ADH not be used to respond to eating salty chips?
eating salty cheaps while increasing Na+ concentration and osmolarity also increases Blood Volume, which opposes the increase in osmolarity.
what stimulates ANP secretion?
stretching of the atria of the heart
what is the mechanism and site of action of ANP?
suppresses reabsorption of Na+ and water in proximal tubules and collecting duct. Inhibits secretion of aldosterone and ADH.
(prevents further increase in BV and BP)
what are the effects of ANP?
increases excretion of Na+ in urine(natriuresis) , increases urine output (diuresis) and thus decreases BV and BP
what are the responses of the body to blood loss(hypovolemic/isotonic)?
Sensed by juxtaglomerular cells and
arterial baroreceptors
↑sympathetic activity
↑ADH and ↑renin/angiotensin
II/aldosterone
Vasoconstriction
Conservation of water and Na+
what is the thirst mechanism for regulating water intake?
what is the order of events that happen in the body in the case of hemorrhage?
- Baroreceptors try to maintain BP
- Try to maintain Osmolarity: fluid shifts
- try to restore Blood Volume: hormones. Takes hours
- takes 7-14 days to replace blood cells
how much blood volume can be lost with BP remaining the same?
10 % ( ~500mL)
