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Physiology Exam 5 > Physiology of the Kidneys > Flashcards

Physiology of the Kidneys Flashcards

1
Q

What is the vessel delivering blood directly to the glomerulus?

A

Afferent arteriole

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2
Q

What is the vessel delivering blood from glomeruli to pertibular capillaries called?

A

Efferent arteriole

-forms the vasa recta

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3
Q

What is the juxtamedullary nephron?

A

Type of nephron that originates in inner 1/3 cortex

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4
Q

What is the juxtamedullar nephron important for?

A

Ability to produce a concentrated urine

-Has longer loop of henley

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5
Q

What are the functions of the collecting duct?

A
  • H20 reabsorption influenced by ADH
  • Secretion
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6
Q

Which of the following is filtered by the glomerulus and thus found in the nephron ultrafiltrate?
RBCs, platelets, proteins, WBCs, or electrolytes

A

Electrolytes

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7
Q

As a result of the large endothelial capillary pores (fenestrae), the glomerular filtration membrane is 100-400x more permeable to?

A

Plasma, H2O and dissolved solutes (than capillaries of skeletal muscles are)

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8
Q

The pores are small enough to prevent the passage of what into the filtrate?

A

RBCS, WBC and platelets

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9
Q

What can pass through the glomerular capillary pores but doesn’t appear in the filtrate because too large to pass through the basement membrane outside the capillary wall/repelled by membrane’s negative charges?

A

Plasma proteins

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10
Q

What is the glomerular filtration rate (GFR)?

A

Volume of filtrate produced by both kidneys each minute

  • Avg 90-120 ml/min (115 in women; 125 in men)
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11
Q

What are the 2 mechanisms to regulate GFR?

A

1) SNS (extrinsic)
2) Autoregulation (intrinsic)
* ****

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12
Q

What is the effect

of increased sympathetic nerve activity on kidney function?

A

When BP falls -> SNS activity VASOCONSTRICTS afferent arterioles -> lowers GFR/UO -> increases blood volume

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13
Q

What happens in cardiovascular shock?

A

Same thing as in SNS activity; lowers glomerular capillary hydrostatic pressure/UO

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14
Q

What keeps the GFR relatively constant?

A

Autoregulation; when MAP falls towards 70 mmHg -> locally produced chemicals released that VASODILATES afferent arterioles

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15
Q

What is the tubuloglomerular feedback?

A

Negative feedback; macula densa cells sense increased flow of filtrate -> VASOCONSTRICT -> lowers GFR/flow of filtrate

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16
Q

How much ultrafiltrate produced a day? How much urine excreted?

A

180 L/day; 1-2 L/day

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17
Q

What is the obligatory water loss?

A

400 ml/day

-Necessary to excrete metabolic wastes

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18
Q

What must occur for reabsorption by osmosis in PCT?

A

[Na+] in ultrafiltrate = 300 mOsm/L (isotonic to plasma) but PCT epithelial cells have lower [Na+]
-Na+ actively transported out of the filtrate, Cl- follows passively by electrical
attraction; H2O follows by osmosis

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19
Q

What % of Na+/Cl-/H2O and K+ reabsorbed?

A

65% Na+/Cl-/H2O; 90% K+

*********

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20
Q

What is the energy expenditure of PCT reabsorption?

A

6% of calories consumed at rest

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21
Q

What happens to tubular fluid entering the loop of Henle?

A

Remains isotonic w/ blood (300 mOsm) even though fluid is reduced 1/3 volume

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22
Q

What is the countercurrent multiplier?

A

LH has positive feedback; [interstitial fluid] x [descending limb fluid] -> osmotic pressure of ISF = 4x that of plasma (hypertonic)

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23
Q

What happens in ascending limb LH?

A

Na+ actively transported to tissue fluid, Cl- passively follows, K+ passively back into filtrate/out basolateral membrane; impermeable to H2O

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24
Q

What happens in descending limb LH?

A

Impermeable to passive diffusion of NaCl; Permeable to H2O (hypertonic ISF -> H2O out of descending limb via osmosis -> saltier filtrate in ascending)

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25
Q

The deepest region of the medulla reaches a concentration of?

A

1400 mOsm/L (max osmolality)

  • Filtrate is 300 mOsm/L coming in
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26
Q

What does the vasa recta do?

A

Countercurrent exchange -> diffusion of salt and water first into and then out of
these blood vessels helps to maintain the hypertonicity of ISF in renal medulla so water can be reabsorbed as filtrate passes through CD

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27
Q

What is permeable to urea?

A

PCT, ascending limb LH, vasa recta and terminal CD

******* (in his notes only talks about ascending limb and terminal CD being permeable)

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28
Q

How is urea recycled?

A

Diffuses out of CD (via urea transporters) and into ascending limb LH

29
Q

The CD’s permeability to H2O depends upon?

A

Presence of ADH

-ADH made by hypothalamus and released from posterior pituitary

30
Q

What happens in absence of ADH?

A

Aquaporin channels are
located in the membrane of intracellular vesicles within CD epithelial cells -> water not reabsorbed -> urine volume will go up

31
Q

What happens in presence of ADH?

A

ADH binds to its membrane receptors on CD -> acts via cAMP**** -> stimulates fusion of
vesicles with plasma membrane -> insertion of the
aquaporin channels into the plasma membrane -> water reabsorption -> urine volume will go down

32
Q

What allows kidneys to rapidly eliminate certain potential toxins?

A

Secretion of substances from peritubular capillaries into ISF -> lumen of tubule -> urine

33
Q

What is the renal clearance rate for inulin?

A

=GFR (120 ml/min)

  • Filtered, not reabsorbed/secreted
  • [renal vein] < [renal artery]
34
Q

What is the renal clearance rate for proteins?

A

0

  • Not filtered
  • [renal vein] = [renal artery]
35
Q

What is the renal clearance for urea?

A

75 ml/min (< GFR)

  • Filtered, 40-60% reabsorbed***** (average 50%)
  • [renal vein] < [renal artery]
36
Q

What is the renal clearance for glucose?

A

0

  • Filtered, completely reabsorbed
  • [renal vein] = [renal artery]
37
Q

What is the renal clearance for PAH?

A

> GFR, =renal plasma flow (625 ml/min)

  • Filtered and secreted
  • [renal vein] < [renal artery]; approaches 0
38
Q

What is the renal clearance for K+?

A

Variable

-Filtered, reabsorbed and secreted

39
Q

What is the formula for renal plasma clearance?

A

(VxU)=P
V=urine volume/min
U=[substance] in urine
P=[substance] in plasma

40
Q

What is the renal transport threshold for glucose?

A

180-200 mg/dl

-Minimum plasma [substance] that results in excretion of that substance in urine

41
Q

Which ion’s regulation is most important for blood volume/pressure?

A

Na+

42
Q

In low Na+ intake, secretion of aldosterone causes what?

A

Na+ reabsorption in cortical CD -> increases Na+ retention in blood

43
Q

What happens in absence of aldosterone?

A

80% of remaining Na+ is reabsorbed in DCT

44
Q

90% filtered K+ is reabsorbed in early part of nephron; where does secretion of K+ occur?

A

In CD

45
Q

What does secretion of K+ depend on?

A

-Amount of Na+ delivered to region
-Amount of aldosterone secreted******
No aldosterone -> No K+ excreted*****

46
Q

What drives secretion of K+ into tubule?

A

As Na+ reabsorbed -> lumen of tubule becomes neg. charged -> potential diff

47
Q

What stimulates secretion of aldosterone?

A

High [K+] or low [Na+]

48
Q

What is the juxtaglomerular apparatus?

A

Region in each nephron where afferent arteriole comes in contact w/ thick ascending limb LH*********
-Related to RAAS

49
Q

What initiates RAAS?

A

Granular (juxtaglomerular) cells within afferent arteriole secrete renin -> angiotensinogen -> angiotensin I
****

50
Q

What acts as an endogenous diuretic by increasing Na+ and H2O excretion?

A

ANP (antagonist to aldosterone)

51
Q

What is ANP produced by?

A

Atria due to stretching of walls

52
Q

How does severe acidosis affect K+/H+ secretion?

A

Increases secretion of H+ and reduces the secretion
of K+ into the filtrate
-Rise in blood [K+] -> hyperkalemia
-Reverse true for alkalosis
-H+ excreted, HCO3- reabsorbed***

53
Q

How does hyperkalemia affect K+/H+ secretion?

A

Increases secretion of K + and thus a decreased secretion

of H+ -> acidosis

54
Q

How do kidneys regulate blood pH?

A

Excreting H+ and reabsorbing HCO3-

-Most H+ secretion occurs in PCT in antiport exchange for Na+

55
Q

What do loop diuretics do?

A

Inhibit NaCl transport out of ascending limb LH

  • e.g. Furosemide
56
Q

What do thiazide diuretics do?

A

Inhibit NaCl reabsorption in the 1st segment of the DCT

57
Q

What is acute renal failure?

A

Ability of kidneys to excrete wastes/regulate homeostasis of blood volume/pH/electrolytes impaired

58
Q

What is there a rise of in acute renal failure? Decrease of?

A

Blood [creatinine]; renal plasma clearance of creatinine

59
Q

What is renal insufficiency?

A

Nephrons are destroyed

60
Q

What are the clinical manifestations of renal insuff?

A

Salt and H2O retention
Uremia
Elevated plasma [H+] and [K+]

61
Q

When glucose transport maximum is reached, ____.

A

Glucose is excreted in urine and not all glucose is reabsorbed

62
Q

Which process is most affected by BP?

A

Glomerular filtration

63
Q

Reabsorption of what occurs via active transport?

A

AAs

64
Q

Eating large amounts of meat will increase the amount of _____ in the blood.

A

Urea

65
Q

Vigorous exercise could lead to high amounts of _____ in urea.

A

Albumin

66
Q

What causes urine to flow from the kidneys to the bladder?

A

Peristalsis

67
Q

The micturition reflex is centered where?

A

Sacral cord

68
Q

What is the formula for quantity of excreted urine?

A

Q (mg/min)=VU
V=rate of urine formation
U=[inulin] in urine
****

Physiology Exam 5 (5 decks)

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