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Urogenital 1 > Production of Urine > Flashcards

Production of Urine Flashcards

1
Q

What is renal autoregulation of GFR?

A

The ability of the kidneys to maintain a constant renal blood flow and GFR.

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2
Q

What two mechanisms control renal autoregulation?

A

Myogenic mechanism

Tubuloglomerular mechanism

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3
Q

What does the myogenic mechanism respond to?

A

Changes in blood pressure.

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4
Q

Explain how the myogenic mechanism responds to changes in blood pressure.

A
  1. As blood pressure increases, renal blood flow and GFR also increase.
  2. In response smooth muscle in the wall of the afferent arteriole constrict, decreasing renal blood flow and returning GFR to normal.

Decreased bp = smooth muscle relaxes increasing renal blood flow and GFR.

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5
Q

What do baroreceptors do?

A

Detect changes in blood pressure.

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6
Q

Vasoconstriction of the afferent arteriole of the glomerulus leads to what?

A

Decreased urine output
Decreased GFR
Increased blood volume and thus pressure

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7
Q

What are the main cells that control tubuloglomerular feedback?

A

Macula densa cells

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8
Q

Explain the role of macula densa cells in tubuloglomerular feedback.

A

Macula densa cells detect increased delivery of Na+ and H2O to the DCT. Macula densa cells send a signal causing the afferent arteriole of the glomerulus to constrict, decreasing GFR and increasing the amount of sodium and water retained by the kidneys.

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9
Q

How do macula densa cells cause constriction of the afferent arteriole?

A

Macula densa cells inhibit the release of NO from the JGA. NO causes vasodilation, so it’s inhibition causes the afferent arteriole to constrict.

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10
Q

What is the renal corpuscle?

A

The combination of the bowman’s capsule and the glomerulus, produces the filtrate.

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11
Q

Where is the majority of water and Na+ reabsrobed?

A

The proximal convoluted tubule.

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12
Q

What is reabsorbed in the PCT?

A

Na+ and water

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13
Q

What is reabsorbed in the descending loop of henle?

A

Water only

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14
Q

What is the THIN ascending limb of the loop of henle permeable to?

A

Only Na+ and Cl-

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15
Q

What is the THICK ascending limb permeable to?

A

K+

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16
Q

What occurs in the DCT?

A

Secretion of ions, acids, drugs and toxins for excretion occurs here.

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17
Q

What does the juxtamedullary nephron allow compared to cortical nephrons?

A

Much greater reabsorption of water

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18
Q

What forms the inner wall of the glomerulus?

A

A visceral layer made of podocytes.

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19
Q

What are the three layers of the filtration membrane?

A

Glomerular endothelial layer
Basement membrane
Podocytes with filtration slits

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20
Q

Explain the role of glomerular endothelial layer in the filtration membrane.

A

The endothelial layer has large fenestrations that allows all solutes to exit the glomerular capillaries, but prevents the filtration of blood cells.

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21
Q

Explain the role of the basement membrane in the filtration membrane.

A

Allows the passage of water and small solutes to enter the filtrate.

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22
Q

What do the glycoproteins on the basement membrane prevent the exit of and how?

A

The negative charges on the glycoproteins prevent the passage of plasma proteins.

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23
Q

What is the basement membrane made of?

A

Small collagen fibres and glycoproteins

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24
Q

Explain the role of podocytes in the filtration membrane.

A

Podocytes have filtration slits between pedicels which allows only the filtration of small molecules.

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25
Q

What are pedicels of podocytes?

A

Small foot like projections.

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26
Q

What do mesangial cells control in the glomerulus?

A

How much surface area is available for filtration affecting rate of GFR.

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27
Q

What do relaxed mesangial cells in the glomerulus equate to?

A

High surface area and thus high GFR.

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28
Q

Explain regarding daltons what molecules are able to pass into the filtrate.

A

Small proteins less than 30,000 daltons are able to pass into the filtrate.
More than 30,000 daltons cannot.

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29
Q

What are daltons are measurement of?

A

The atomic mass of proteins.

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30
Q

What is the net filtration pressure?

A

The total pressure that promotes filtration.

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31
Q

What is the equation for NFP?

A

NFP = GBHP - CHP - BCOP

GBHP - glomerular blood hydrostatic pressure
CHP - capsular hydrostatic pressure
BCOP - Blood colloid osmotic pressure

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32
Q

What is glomerular blood hydrostatic pressure?

A

The blood pressure in hydrostatic capillaries that forces water and solutes through the filtration membrane.

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33
Q

What is capsular hydrostatic pressure?

A

The hydrostatic pressure extered against the filtration membrane by fluid already in the capsular space and renal tubule.

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34
Q

What is blood colloid osmotic pressure?

A

The pressure from proteins such as albumin and globulins in blood plasma that oppose filtration.

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35
Q

What is the glomerular filtration rate?

A

The amount of filtrate formed in all renal corpuscles per minute in both kidneys.

36
Q

What is the equation for GFR?

A

GFR = (U x V)/P

U = solute conc in urine
V = volume of urine excreted per min
P = solute concentration in plasma
37
Q

What happens when GFR is to high?

A

Substance may not have enough time to be reabsorbed.

38
Q

What occurs when GFR is to low?

A

To much filtrate will be reabsorbed, and not enough waste will be excreted.

39
Q

By what three ways is GFR controlled?

A

Renal autoregulation
Neural regulation
Hormonal regulation

40
Q

By what two methods is GFR altered?

A

Changing the glomerular capillary surface area available for filtration.
Adjusting blood flow into and out of the glomerulus.

41
Q

Through what receptor does norepinephrine cause vasoconstriction?

A

Alpha-1 receptors

42
Q

What occurs when norepinephrine binds Alpha-1 receptors?

A

Vasoconstriction of the smooth muscle of arterioles.

43
Q

Through what divsion of the nervous system does neural regulation occur?

A

The sympathetic division of the ANS by norepinephrine

44
Q

What neurotransmitter is responsible for the neuroregulation of the kidneys?

A

Norepinephrine

45
Q

When does neuralregulation occur?

A

Exercise or blood loss

46
Q

Explain the process of neuroregulation.

A
  1. Norepinephrine binds to it’s Alpha-1 receptor.
  2. Sympathetic stimulation causes the afferent arteriole to constrict decreasing bloodflow through the glomerulus.
  3. GFR decreases.
    - –> this decreases urine output, conserving blood volume.
    - –> Enables more blood flow to other tissues.
47
Q

What are the two hormones involved in the hormonal regulation of GFR?

A

Angiotensin II

Atrial natriuretic peptide

48
Q

What is angiotensin II role in hormonal regulation of GFR?

A

A II causes vasoconstriction of both arterioles decreasing renal blood flow and thus GFR.

49
Q

What causes the secretion of atrial natriuretic peptide?

A

ANP is scereted by the atrial cells of the heart when the atria strech due to increased blood volume.

50
Q

What does ANP cause?

A

Mesangial cells of the glomerulus to relax increasing the capillary surface area available for filtration. Thus GFR rises and blood volume and blood pressure falls.

51
Q

What substance is used to determine GFR?

A

Creatinine

52
Q

Why is creatinine used to determine GFR?

A
  1. It is freely filtered
  2. It is not secreted or reabsorbed
  3. It is not toxic
  4. It is not metabolised
53
Q

What is a more accurate alternative to creatinine for determining GFR?
How is it administered?

A

Inulin, adminster by IV.

54
Q

What is reabsorbed into the peritubular capillaries and why?

A

Water as the peritubular capillaries are connected to the efferent arteriole and thus have a high colloid osmotic pressure and low hydrostatic pressure as the majority water and ions were filtered out in the glomerulus.

55
Q

What does the PCT secrete into urine?

A

H+
NH4+
Urea

56
Q

What is reabsorbed in the PCT?

A

Na+, glucose, water and bicarbonate ions

57
Q

Through what receptor is Na+ reabsorbed in the PCT?

A

Na+ H+ antiporter

Na+/K+ pump 3/2

58
Q

What proteins are present on the PCT membrane that facilitates the reabsorption of water?

A

Aquaporin-1 molecules

59
Q

Explain the breakdown of where in the nephron is Na+ reabsrobed?

A

65% of Na+ reabsorbed in the PCT
25% of Na+ in loop of henle
8% of Na+ in DCT
2% reabsorbed in the collecting duct

60
Q

What is the descending loop of henle permeable to?

A

Only water

61
Q

Explain the permeability of the ascending loop of henle.

A

Impermeable to water.
Thin portion permeable to Na+ and Cl-
Thick portion permeable to K+

62
Q

Where in the nephron is all of the glucose reabsorbed?

A

The PCT

63
Q

Explain the counter current multiplier system of the loop of henle.

A

The peritubular capillaries run in the opposite direction to that of the tubular fluid, causing a concentration gradient to be maintained throughout the loop.

64
Q

Explain specifically the multiplier component of the CCM system.

A

Multiplier as the blood travelling by the ascending limb has no solutes, and thus solutes diffuse from the ascending limb into the PC.
Water in the descending limb then enters the PC due to the now high concentration of solutes now in the blood.

65
Q

What changes in charge occur in the ascending limb?

A

None it is electrochemically neutral.

66
Q

What are the effects of hyperglycaemia on podocytes?

A

Hyperglycaemia causes gaps between podocytes to form. This allows larger proteins to move into the filtrate and into the urine.

67
Q

What is reabsorbed in the early DCT?

A

Na+ and Cl- by symporters
Na+ by Na+/K+ pumps
Ca2+ when PTH stimulates it’s reabsorption

68
Q

What is reabsorbed in the late DCT?

A

Na+

69
Q

What is secreted in the late DCT?

A

K+

70
Q

What controls the Na+ reabsroption in the late DCT?

A

Aldosterone through increased activity of the Na+/K+ pumps.

71
Q

What cells does aldosterone act upon?

A

Principle cells in the late DCT and CD

72
Q

ADH is also known as…

A

Vasopressin

73
Q

Where is ADH released?

A

Anterior pituitary

74
Q

What does ADH do specifically?

A

ADH causes vesicles containing aquaporin-2 molecules to insert into the membranes of principle cells on the late DCT and CD.

75
Q

What is the result of ADH secretion?

A

Increased reabsorption of water increasing blood volume and thus blood pressure.

76
Q

Where are aquaporin-2 channels found?

A

Principle cells in the late DCT and CD

77
Q

Where are aquaporin-1 channels found?

A

PCT and and descending loop of henle

78
Q

What do osmoreceptors detect?

A

High Na+ concentrations in the blood.

NOT WATER!

79
Q

What is the pH of ECF?

A

7.35-7.45

80
Q

What does carbonic anhydrase in RBC’s lead to the formation of?

A

Bicarbonate

81
Q

What is the chloride shift?

A

The diffusion of bicarbonate down it’s concentration gradient in exchange for Cl-

82
Q

What mediates the chloride shift?

A

Band 3 (a membrane protein)

83
Q

How does pH correction occur in the kidneys?

A

The kidney can reabsorb bicarbonate and excrete H+ and NH4+ to maintain pH.

84
Q

What is meant by isomolar urine?

A

A measure of urine concentration, in which large values indicate concentrated urine and small values indicate diluted urine.

85
Q

What renal autoregulation mechanism do macula densa cells control?

A

Tubuloglomerular feedback

Urogenital 1 (12 decks)

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