Renal Physiology Part 3 Flashcards Preview

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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

Anion gap

-differential diagnosis of metabolic acidosis
-cations - anions (sodium - (chloride + bicarbonate)
-Normal range: 8-11
-anion gap is either normal or increased, depending on cause of metabolic acidosis