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Biol 1412 > Topic 15 > Flashcards

Topic 15 Flashcards

1
Q

Kidney functions

A
  • maintain plasma voltume (bp MAP)
  • regulate ion and H2O
  • acid base balance
  • eliminate waste, drugs and hormones
  • endocrine
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2
Q

Nephron

A

functional unit of kidney = renal corpuscle and tubule.

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3
Q

Processes in nephron leading to urine formation

A
  • glomerular filtration
  • tubular reabsorption
  • tubular secretion
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4
Q

Glomerular filtration

A

20% of plasma in glomerulus is filtered into bowman capsule (bulk flow across filtration membrane)

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5
Q

Filtration membrane of glomerular

A
  • fenestrated endothelium
  • fused basement membranes
  • podocytes with filtration slits between
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6
Q

Glomerular filtrate

A
  • identical to plasma minus large protein
  • H2O, glucose, aa, vitamins, ions, urea, some small proteins
  • pH 7.45
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7
Q

Net filtration pressure (NFP) =

A

(55+0) - (30+15) = 10 mmHg

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8
Q

Glomerular filtration pressure (GFP)

A

at this NFP, 180L/day filtrate both kidneys = 125 mL/min (entire plasma vol. filtered 65x/day). however <1% of filtered volume remains at end of collecting duct (reabsorption)

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9
Q

Regulation of GFR

A

keeps GFR from changing when bp changes. if not increase MAP and increase GFR (vice versa)

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10
Q

Intrinsic regulation (auto regulation) of GFR

A

for bp in range of resting to moderate exercise.

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11
Q

Intrinsic regulation of GFR in the myogenic

A

⇑MAP ⇒ stretch ⇒ afferent arteriole smooth muscle contracts ⇒ prevents ⇑BP in glomerulus (+ vice versa)

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12
Q

Extrinsic regulation

A

primarily SNS (arteriolar vasocon.)

  • afferent low flow into glom
  • efferent blood backs up in glom
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13
Q

Moderate SNS activation

A

both balance and GFR dent change much. (extreme stress, heavy exercise, hemorrhage is high GFR)

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14
Q

NFP can change blood OP (proteins)

A
  • dehydration causes high BOP and low GFR

- burns, nephrotic syndrome causes low BOP and high GFR

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15
Q

NFP can change capsular hydrostatic P

A

-urinary tract obstruction (kidney stone, inflammation, rotate enlargement) causes high CHP and low GFR

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16
Q

Tubular reabsorption

A

1-1.5 L/day urine but 180 L/day filtered so 99% filtrate reabsorbed from tubules into peritubular and vasa recta capillaries

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17
Q

Active tubular reabsorption

A

requires energy. (Na, ions, glucose, aa)

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18
Q

Passive tubular reabsorption

A

no energy required. (Cl, H2O, urea.

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19
Q

Proximal convoluted tubule (PCT) (unregulated)

A
  • -glucose, aa – 100% - act. transport
  • -NaCl - 66% - act. transport
  • -small proteins (endocytosis ⇒ aa ⇒ blood)
  • -vitamins
  • -obligatory (unregulated) reabsorption of H2O (osmosis as solutes reabsorbed ⇒ water “obliged” to follow)
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20
Q

Result of proximal convoluted tubule

A
  • large amount of solute removed + ⇓ filtrate volume

- filtrate is isotonic to plasma = 300 mOsmoles/L (mOsm/L = unit of OP)

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21
Q

Loose of henle

A

reabsorbs into vasa recta from:

  • descending limb (DL): h2o only
  • ascending limb (AL): NaCl only
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22
Q

Distal convoluted tubule (ACT)

A

initial part. reabsorbs Na, Cl, Ca. impermeable to h2o

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23
Q

Late DCT and collecting duct (CD)

A

reabsorb Na which increases aldosterone and decreases atrial natriuretic peptide ANP. facultative reabsorption of h2o. ADG increase (ANP inhibits ADH)

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24
Q

Nephrons normally reabsorb…

A

→ 99% of filtered H2O
→ 99.5% of filtered NaCl
→ 100% of filtered glucose
→ 50% of filtered urea

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25
Q

Filtrate may contain ..

A

trace aa and proteins (depends on diet) but no glucose or blood

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26
Q

Tubular secretion

A

from peritubular blood into filtrate.

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27
Q

Main substances secreted from tubular..

A
    • wastes e.g. urea, uric acid, some hormones
    • K+ (⇑ by aldosterone)
    • H+ or NH4+ ⇒ maintains blood plasma pH
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28
Q

Counter current multiplier mechanism

A

tubular reabsoption. permits excretion of urine that is dilute (100 mOsm/L) to concentrated (1200 mOsm/L). produces/ maintances vertical osmotic gradient = increase solute in ISF as you move deeper into medulla.

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29
Q

Within loop of henle

A
  • – fluid flows in parallel tubes (DL, AL) in opposite directions
  • – DL - permeable to H2O, impermeable to NaCl
  • – AL - impermeable to H2O, permeable to NaCl - NaCl
  • – As filtrate moves down DL - H2O into ISF (osmosis)
  • – Highly concentrated filtrate enters AL. NaCl pumped out against gradient (200mOsm/L gradient)
  • – filtrate leaving AL ( = 150 mOsm/L) is lower osmolarity than plasma due to AL imperm to H2O and AL NaCl pump
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30
Q

Within early DCT

A

more salt removed from filtrate (reabsorbed), no H2O removed ∴ 100 mOsm/L when enters late DCT

31
Q

Urine production

A

filtrate 100 mOsm/L enters late DCT, CD

32
Q

Concentrated urine

A

dehydrated, low bp. in late DCT, CD aldosterone increase Na reabsorb and ADH increase facultative H2O reabsorb. urine can be up to 1200 mOsm/L

33
Q

Dilute urine

A

excess plasma h2o, high bp. in late DCT CD ANP inhibits ADH, aldosterone. impermeable to h2o, NaCl

34
Q

Average urine passed per day

A

1-1.5 L/day

35
Q

Hormonal regulation of urine renin angiotension system

A

renin from juxtaglomerular cells (modified smooth muscle cells of aff. and eff. arterioles).

36
Q

Renin angiotension system: high renin when..

A
    • ⇓ stretch of juxtaglomerular cells (i.e. ⇓ bp or blood volume)
    • ⇑ SNS activity
    • ⇓ NaCl in filtrate (detected at macula densa)
37
Q

Renin angiotension system: low renin when…

A
    • ⇑ stretch of juxtaglomerular cells (i.e. ⇑ bp or blood volume)
    • ⇑ ADH, angio II
    • ⇑ NaCl in filtrate
    • ⇓ SNS activity
38
Q

Renin converts..

A

angiotensinogen to angiotensin I, which is then activated to angiotensin II by angiotensin-converting enzyme (ACE)

39
Q

ADH

A

high facultative reabsorbs h2o (late DCT, CD)

40
Q

ADH high if..

A
  • – low blood vol or P
  • – ⇑ plasma osmolarity (concentration)
  • – ⇑ angio II
  • – nicotine, nausea
41
Q

ADH low if..

A
  • – reverse of high ADH
  • – high ANP
  • – alcohol
42
Q

Diabetes insipidus

A

no ADH or no receptors. large vol. of dilute urine, ⇑ thirst, normal blood + urine glucose

43
Q

Aldosterone (steroid hormone)

A
    • ⇑ ald when angio II, high plasma K+
    • turns on genes that ⇑ # of Na+/K+ ATPase in late DCT, CD
  • – ⇑ Na+ reabsorption in late DCT, CD ∴ H2O follows (osmosis, if ADH present), Cl- follows (charge)
  • – ⇑ K+ secretion
44
Q

Atrial Natriuretic Peptide (ANP)

A

⇑ by ⇑ bp. result = ⇓ renin (∴ angio II), ⇓ ADH, ⇓ aldost, ⇓ vasocon ⇒ ⇑ urine vol

45
Q

High SNS impulses

A

aff. + eff. arterioles constrict

46
Q

Low SNS impulses

A

aff. + eff. arterioles relax

47
Q

Myogenic response (stretch causes constriction) is..

A

powerful in kidney..

48
Q

If high MAP

A

⇑ flow to kidney causes vasocon. (myogenic), in spite of ⇓ SNS, renin, angio II + ⇑ ANP (result of these = ⇓ vasocon.) ⇒ GFR returns to resting

49
Q

Lack of ADH, aldosterone means the urine will be dilute ..

A
    • blood volume will ⇓ (urine volume high) ∴ MAP ⇓

- -extrinsic signals correct bp, intrinsic mechanism keeps GFR constant

50
Q

If large drop in bp or volume ..

A

vascon. signals stronger than intrinsic mechanisms ⇒ get ⇓ in GFR

51
Q

Normal urine constituents

A
  • h2o
  • nitrogenous wastes
  • regulated substances
  • pH 4.5 to 8.0 (average 6)
52
Q

Nitrogenous wastes in urine

A
    • urea: from aa metabolism (50% reabsorbed)
    • uric acid: from nucleic acid breakdown. secreted. 10% reabsorbed. poorly water soluble and accumulation= gout or kidney stones.
    • creatinine: breakdown of creatine in skel. muscle. production/excretion contact. no reabsorption. used to estimate GFR (indicate kidney disease before symptoms)
53
Q

Micturition (bladder) reflex

A

kidney to ureters to urinary bladder then contraction of sm. muscle (detrusor) produces P gradient to the urethra

54
Q

Renal plasma clearance (PC)

A

volume of plasma cleared of a substance each mind (rate a substance is removed blood by kidney) used to estimate time a substance remains in blood

55
Q

PC of substance “A”

A

[A] in arterial plasma

56
Q

Inulin (CHO from daffodils can be used…

A

to estimate GFR. its filtered by not reabsorbed, secreted, metabolized so amount of urine = amount filtered

57
Q

If PC

A

substance is reabsorbed from filtrate

58
Q

If PC>GFR

A

substance is serviette into filtrate

59
Q

Acid base balance

A

regulation of free H in ECF. H normally produced by metabolism

60
Q

H buffered to prevent change in pH then eliminated by..

A
  • respiratory system

- renal system

61
Q

Buffer systems =

A

pairs of chemicals..

  • bases take up H
  • acids give up H
  • balance of 2 minimizes pH change
62
Q

Major buffer in blood

A

Bicarbonate system

63
Q

Other buffers are..

A
  • Hb + H HbH in rbc

- proteins –> cells, plasma

64
Q

Respiratory system in control of acid base balance

A

eliminates CO2, short term solution. if high H get hyperventilation. is low H get hypoventilation

65
Q

Renal system in control off acid base balance

A

eliminates H form metabolically produced acids. secretes H into tubule lumen. converse and increases blood HCO3

66
Q

For each H secreted, 1 HCO3 enters blood to remove H and maintain/increase HCO3..

A
  • – H+ (as H+) lost in urine, 1 HCO3- gained in blood
  • –secreted H+ combines with filtered HCO3- ⇒ CO2 + H2O in lumen
  • -no H+ is lost, but HCO3- is “reabsorbed” indirectly to maintain buffer
  • – secreted H+ combines with filtered Pi ⇒ lost in urine
      • result: 1 H+ (as HPi) lost, 1 HCO3- gained to blood
  • – 2 ammonia (NH3) formed from 1 glutamine (aa) in tubule cell and combine with H+ to form 2 ammonium ions (NH4+)
    • -result: 2H+ (as NH4+) lost and 2 HCO3- gained to blood
67
Q

Acidosis

A

plasma pH < 7.35 (excess H) CNS depressed will result in coma, irregular heart beat. urine will contain H, HP, NH4, little HCO3

68
Q

Respiratory acidosis

A

arterial PCO2 increase, H increase, pH decrease. due to hypoventilation (lung disease). lungs cannot compensate.kidneys increase H secretion and HCO3 into blood

69
Q

Metabolic acidosis

A

high H from any source other than CO2. lungs increase ventilation (due o high H at peripheral chemoreceptors) and low H (but central chemoreceptors will eventually decrease ventilation due to low CO2), kidneys (if not damaged) will increase H secretion and HCO3 into blood

70
Q

Example of metabolic acidosis

A
  • diarrhea: loss of HCO3
  • uncontrolled diabetes mellitus: high fat metabolism to keto acids
  • strenuous exercise: lactic acid
  • renal failure
71
Q

Alkalosis

A

pH> 7.45 (fewer H). over excitation of the CNS, spasms in skel. muscle. urine will contain HCO3, no HP, no NH4 and little H

72
Q

Respiratory alkalosis

A

arterial Pco2. due to hyperventilating. (anxiety) lungs cannot compensate. kidneys decrease secretion of H so low HCO3 to blood (lost in urine)

73
Q

Metabolic alkalosis

A

caused by any reason but respiratory. (ex: excess vomiting, ingestion of alkaline drugs). lungs decreased H causes vent to decrease and high arterial CO2 and high H (eventually high CO2 will increase ventilation) kidneys decrease secretion of H and lower HCO3 to blood (lost in urine)

Biol 1412 (15 decks)

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