Flashcards in Renal Physiology Part 3 Deck (58)
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1
Countercurrent multiplier mechanism
-concentrates solute in medullary interstitium via 2 primary mechanisms:
-Na-K-2Cl cotransporter reabsorption of Na in the TAL
-reabsorption of urea initiated by ADH
-high solute concentration enables kidneys to excrete highly concentrated urine, conserve water during periods of dehydration
-this mechanism requires integrated function of descending, ascending limbs; vasa recta capillaries; collecting ducts
2
Any drugs which increase renal blood flow to vasa recta or inhibit the loop transporter will
decrease the renal medullary interstitial osmolarity and reduce the kidney's ability to produce a concentrated urine
3
ADH
-increase H2O and urea permeability of late distal tubule, collecting duct
-stimulates water reabsorption in principal cells via V2 receptor
-also vasoconstrictor arterioles (V1 receptor) and thus can serve as a hormonal regulator of vascular tone
4
2 primary regulators of ADH are
-plasma osmolality: an increase stimulates, while a decrease inhibits
-blood pressure/volume: an increase inhibits, while a decrease stimulates
5
In well-hydrated individuals (diuresis) collecting duct
is normally impermeable to water
-water remains in tubular lumen; dilute urine is excreted
-low ADH
6
In dehydrated individuals (antidiuresis) collecting duct
is highly water-permeable
-water is reabsorbed; low volume of concentrated urine is excreted
-high ADH
7
ADH promotes urea
reabsorption from inner medullary collecting duct by increasing expression of urea transporters
8
Antidiuresis: high ADH
-ADH makes the collecting duct epithelial highly water permeable
-water is reabsorbed in this segment, and a low volume, highly concentrated urine is excreted
-SIADH, dehydration
9
Water diuresis: low ADH
-high volume of dilute urine is excreted
-collecting duct epithelium is impermeable to water
-lower solute concentrations in medullary interstitium
-diabetes insipidus, volume expansion
10
ANP
-increases GFR: afferent arteriolar dilation, efferent arteriolar constriction
-inhibits Na+ reabsorption in medullary CD
-suppresses renin secretion
-suppresses aldosterone secretion
-a systemic vasodilator
-suppresses AVP secretion, actions
11
Free water clearance (Ch2o)
excretion of solute-free water by the kidneys
-Ch2o=V-Cosm
12
If Uosm
positive; pure water is cleared from the body
13
If Uosm > Posm, Ch2o
is negative; pure water is retained
14
Fractional Excretion
(Una x Pcreat)/(Pna x Ucr) x 100
15
Fractional excretion below 1%
-prerenal and AGN
-Na avidly reabsorbed
16
Fractional excretion greater than 2%
-ATN, renal
-tubular damage disrupts normal Na reabsorption
17
3 lines of defense against pH changes
-chemical buffers
-respiration
-kidneys
18
6 factors control renal H+ secretion
-intracellular pH, plasma Pco2, carbonic anhydrase, Na+ reabsorption, extracellular K+, aldosterone
19
Respiratory acid-base disturbances:
-primary changes in Pco2 cause H+ and HCO3- to change
20
Metabolic acid-base disturbances
-gains or losses of H+ and HCO3-; respiratory, renal responses
21
H+ competes with
Ca2+ for binding sites on plasma proteins
22
Acidemia
increased [H+] = increase plasma free [Ca2+]
-hypercalcemia
-decreased pH--H+ displaces Ca2+ from proteins
23
Alkalemia
decreased [H+] = decreased plasma free [Ca2+]
-hypocalcemia
24
Acidosis
-increased H+
-hyperkalemia
-K+ shifting out of cell into ECF
-Na+ shifting out of cell into ECF
-H+ moving into cell
25
Alkalosis
-hypokalemia
-decreased H+
-H+ moving out of cell
-K+ moving into cell
-Na+ moving into cell
26
Respiratory alkalosis
-decreased CO2+; equation shifted towards CO2
-compensate by decreasing HCO3-; pH increases
-PCO2
27
Respiratory acidosis
-increased CO2+; equation shifted towards HCO3-
-compensate by increasing HCO3-; pH decreases
-PCO2>40
-renal compensation
28
Metabolic alkalosis
-increased HCO3-; equation shifted towards CO2
-compensate by increasing CO2; pH increases
-HCO3- > 24
-respiratory compensation
29
Metabolic acidosis
-decreased HCO3-; equation shifted towards HCO3-
-compensate by decreasing CO2; pH decreases
-PCO2
30
