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Physio II > Tubular Reabsorption & Secretion(C)- Exam 3 > Flashcards

Tubular Reabsorption & Secretion(C)- Exam 3 Flashcards

1
Q

What affects tubular reabsorption (keeping it relatively constant)?

A 
Glomerulotubular balance
Peritubular Capillary and interstitial forces
Arterial blood pressure
Hormonal control
Sympathetic nervous effect
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2
Q

Can reabsorption of solutes be controlled independently?

A

Reabsorption of some of them can

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3
Q

What does glomerulotubular balance allow?

A

Increase in reabsorption rate when there is an increase in tubular load (increased tubular inflow); maintains sodium and volume homeostasis; prevents large changes in fluid flow to distal tubules ven though there have been significant changes in MAP

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4
Q

If GFR went from 125 mls/min to 150 mls/min rate of reabsorption in proximal tubule would do what?

A

80 mls/min (65% of GFR) to 97.5 mls/min (65% of GFR)

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5
Q

What is the normal net force for reabsorption in peritubular capillary?

A

10 mmHg

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6
Q

What are the 4 peritubular capillary forces?

A

IN: Pif=6 mmhg; cap oncotic P=32 mmHg
OUT: Pc=13 mmHg; intersti. cap oncotic= 15 mmHg

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7
Q

Filtration coefficient is…

A

Reabsorption rate/net force; large

124mls/min / 10 mmHg = 12.4 mls/min/mmHg

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8
Q

What affects filtration coefficient?

A

Transfer surface area and hydraulic conductivity (permeability)

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9
Q

What factors affect peritubular capillary reabsorption?

A

Peritubular hydrostatic pressure (PHP)
Peritubular oncotic pressure (POP)
Renal interstitial hydrostatic pressure
Renal intersitial oncotic pressures

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10
Q

What happens to reabsorption is peritubular hydrostatic pressure goes up?

A

Decrease in reabsorption

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11
Q

What happens to reabsorption if peritubular oncotic pressure goes up?

A

Increase in reabsorption

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12
Q

What affects peritubular hydrostatic pressure?

A

Arterial pressure

Resistance of afferent and efferent arterioles

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13
Q

Increase in arterial P = __________ in PHP = _________ reabsorption

A

increase, decrease

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14
Q

Increase in resistance of afferent arterioles = __________ PHP = _______ reabsorption

A

decrease, increase

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15
Q

What affects peritubular oncotic pressure?

A 
Plasma protein concentration
Filtration fraction (GFR/RPF)
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16
Q

Increase plasma protein concentration = ________ plasma oncotic pressure = ________ POP= ______ reabsorption

A

increased, increased, increased

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17
Q

Increased GFR or Decreased BF causes an _________ filtration fraction

A

Increased

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18
Q

Increased filtration fraction = _______protein concentration (_____fluid is actually filtered)

A

increased, more

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19
Q

Increased protein concentration = ___________POP = _______ reabsorption

A

increased, increased

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20
Q

Decreased capillary reabsorption= ___________ in interstitial solute and interstitial water= _______interstitial hydrostatic pressure and ______ in interstitial oncotic P= ______ net movement of solute/water from tubule to interstitial spaces

A

Increased, increased, decreased, decreased

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21
Q

Under normal reabsorptive conditions, describe the back flow of water and solute from interstitial spaces to tubular lumen?

A

Always a back flow; tight junctions not very tight espcially in proximal tubule

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22
Q

Decreased peritubular reabosprtion = ______ solute and water accumulation in interstitial space= _______ backflow of solute and water from interstitial space to tubular lumen

A

increased, increased

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23
Q

Forces that increase peritubular capillary reabsorption also do what?

A

Increase movement of solute and water (reabsorption) from the tubular lumen to the renal interstitial spaces

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24
Q

Increased filtration coefficient = _______ Reabsorption

A

Increased

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25
Q

How does capillary surface area relate to filtration coefficient and reabsorption?

A

Increased surface area
Increased filtration coefficient
Increased reabsoprtion

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26
Q

How does capillary permeability relate to filtration coefficient and reabsorption?

A

Increased permeability
Increased filtration coefficient
Increased reabsorption

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27
Q

How much does the filtration coefficient change under most conditions? What can affect it?

A

Coefficient remains constant under most physiologic conditions. Will be affected by renal disease.

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28
Q

Autoregulation works to keep what constant as pressure changes?

A

GFR and RBF

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29
Q

Under what pressure range does autoregulation work?

A

75 mmHg to 160 mmHg

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30
Q

Even though autoregulation is involved, there is a small increase in _______, which results in an increase in _________.

A

GFR; urine output

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31
Q

Arterial pressure increase = Small ______ in the amount of sodium and water reabsorbed.

A

decrease

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32
Q

Small increase in peritubular capillary hydrostatic pressure= _______ renal interstitial hydrostatic pressure = _______backflow of solute and water

A

Increased; increased

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33
Q

Arterial Pressure increases= Angiotensin II ________.

A

decreased

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34
Q

Decreased Angiotensin II = less stimulation of what?

A

Sodium reabsorption

Aldosterone production; less stimulation of sodium reasborption

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35
Q

Kidneys must be able to respond to changes in _______ of specific substances without changing ______ of the substances.

A

Intake; output

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36
Q

What provides the control specificity needed to maintain normal body fluid volumes and solute concentrations?

A

Hormone secretion

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37
Q

Aldosterone: Site of Action; Effects

A

Site of Action: Collecting duct/tubule
Effects: increased NaCl, H20 reabsorption
Increased K+ secretion

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38
Q

Angiotensin II: Site of Action; Effects

A

Site of Action: Proximal tubule; thick ascending loop of henle/distal tubule; collecting duct

Effects: Increased NaCl, H20 reabsorption
Increased K+ secretion

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39
Q

ADH: Site of Action; Effects

A

site of action: distal tubule; collecting tubule and duct

effects: increased H20 reabsorption

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40
Q

Atrial natriuretic peptide: Site of Action; effects

A

Site of action: distal tubule; collecting tubule and duct

Effects: decreased NaCl reasborption

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41
Q

Parathyroid hormone: Site of action; effects

A

Site of action: proximal tubule; thick ascending loop of henle; distal tubule
Effects: decreased PO4– reabsorption
Increased Ca++ reasborption

42
Q

What secretes aldosterone?

A

Zona glomerulosa in adrenal cortex

43
Q

What is the function of aldosterone?

A

Regulates sodium reabsorption and potassium secretion; very important regularly of [K+]

44
Q

What is the principal site of action of aldosterone?

A

Principal cells of cortical collecting tubule; stimulates increased Na-K ATPase activity (basolateral locations)
Increases permeability of luminal side membrane to sodium

45
Q

What stimulates increased release of aldosterone?

A

Increased extracellular potassium concentration

Increased angiotensin II levels (sodium/volume depletion or low arterial pressure)

46
Q

What disease is the absence of aldosterone?

A

Addison’s disease; adrenal malfunction or destruction

47
Q

What disease is an excess of aldosterone?

A

Adrenal tumors; Conn’s syndrome

48
Q

What is the most powerful sodium-retaining hormone?

A

Angiotensin II

49
Q

What causes increased production of angiotensin II?

A

Low blood pressure and/or low ECF volume

50
Q

Angiotensin II stimulates the secretion of what?

A

Aldosterone; resulting in increased sodium reabsorption

51
Q

What is angiotensin II’s effect on the efferent arterioles?

A

Constricts efferent arterioles; increased sodium and water reabsorption

52
Q

What is the purpose of angiotensin II constricting effect arterioles?

A

Helps ensure that normal exertion rates of metabolic wastes are maintained by helping to maintain normal rates of GFR; able to retain sodium and water without retaining metabolic waste

53
Q

Angiotensin II directly stimulates sodium reabsorption where?

A

Proximal tubules, loop of henle, distal tubules, and collecting tubules.

54
Q

Angiotensin II stimulates which pumps?

A
  1. Increased Na/K ATPase activity of tubular epithelial cells (basolateral membrane)
  2. Na/H exchange in proximal tubule (luminal membrane)
  3. Na/Bicarb co transport (basolateral membrane)
55
Q

Angiotensin II affects transport on which membranes?

A

Luminal and basolateral membranes

56
Q

Where is angiotensin II “very active”

A

proximal tubule

57
Q

What is vasopressin?

A

ADH

58
Q

Where is ADH made?

A

Hypothalamus

59
Q

Two types of _______ produce ADH.

A

Magnocellular (large) neurons

60
Q

Where are the neurons located that make ADH?

A

Supraoptic (87%) and paraventricular (17%) nuclei (hypothalamus)

61
Q

What happens to ADH once it is produced?

A

Moves down the neurones to their tips which are located in the posterior pituitary

62
Q

Where is ADH released?

A

Neurons in the posterior pituitary

63
Q

How is ADH released?

A

Stimluation of the supraoptic and paraventricular nuclei (increased osmolarity) sends impulses down the magnocellular neurons which stimluates release of ADH from storage vesicles located in the nerve endings

64
Q

Decreased ADH = ______ water permeability= _______ urine volume and _____solute

A

decreased, increased, decreased; results in large volumes of dilute urine

65
Q

ADH stimulates the formation of water channels where?

A

Across the luminal membrane

66
Q

What does ADH bind with? What does this do?

A

Specific V2 receptors; increases formation of cyclic AMP and activation of protein kinases

67
Q

What does protein kinase activation result in?

A

Movement of aquaporin-2 to luminal side of cell

68
Q

Aquaporin-2

A

intracellular protein

69
Q

What do aquporin-2’s do?

A

Come together and fuse with cell membrane to from water channels which increases membrane permeability to water (increases water reabsorption)

70
Q

What increases the formation of aquaporin-2 molecules?

A

Chronic increases in ADH

71
Q

AVP

A

arginine vasopressin

72
Q

Where are V2 receptors?

A

Basolateral membranes

73
Q

Increased ADH in the plasma results in movement of ADH from where to where?

A

From peritubular capillaries to renal interstitial space

74
Q

WHat provides water channels on the basolateral membrane?

A

aquaporins; no evidence to show that they are affected by [ADH]

75
Q

What does decreased ADH result in as far as the aquaporin-2?

A

Movement of the aquaporin-2 molecules back into the cytoplasm which reduces the number of water channels and decreased water permeability

76
Q

Where is atrial natriuretic peptide secreted?

A

Cardiac atrial cells when atria distended by plasma volume expansion

77
Q

What is the action of atrial natriuretic peptide?

A

Direct inhibition of sodium and water reabsorption (especially collecting ducts)
Inhibits renin secretion (thus inhibits angiotensin II formation)

78
Q

What is an important response to help prevent sodium and water retention during heart failure?

A

Atrial natriuretic pepide

79
Q

What is the most important hormone for regulating calcium?

A

Parathyroid hormone

80
Q

What is the action of parathyroid hormone?

A

Increases calcium reabsorption (distal tubules)
INhibits phosphate reabsorption (proximal tubule)
Increases magnesium reabsorption (loop of henle)

81
Q

Severe SNS stimulation = _________(constriction/dilation) of renal arterioles= ______ GFR

A

Constriction of renal arterioles, decreases GFR

82
Q

Low levels SNS stimulation activate what?

A

Alpha receptors on renal tubular epithelial cells (proximal tubule, thick ascending limb of loop of henle, maybe distal tubule); receptor activation stimulates sodium reabsorption which decreases water and sodium excretion

83
Q

SNS stimulates the release of what ?

A

Renin (angiotensin II) which adds to increase in tubular reabsorption of sodium

84
Q

Renal clearance

A

volume of plasma that is completely cleared by kidneys per unit time

85
Q

Why is renal clearance not realistic?

A

No volume of blood completely cleared

86
Q

Renal clearance provides what?

A 
Way to quantify excretory function of kidneys
Quantify RBF
Quantify glomerular filtration
Qunatify tubular reabsoprtion
Quantify tubular secretion
87
Q

What is the equation for renal clearance?

A 
Cs = Us x V / Ps
Clearance= urinary excretion rate/ [plasma]
Cs= clearance of solute (mls/min)
Us= urine concentration of solute (mg/ml)
V= urine flow (mls/min)
Ps= plasma concentration of solute (mg/ml)
88
Q

Clearance of what should be equal to GFR?

A

Inulin

89
Q

When is the excretion rate the filtration rate?

A

Solute is freely filtered and neither reabsorbed nor secreted

90
Q

How much of creatinine is reabsorbed?

A

Small amount

91
Q

How do you make a rough estimate of changes in GFR?

A

Look at changes in creatinine concentration; a four fold increase in creatinine concentration means the GFR is one-fourth normal

92
Q

When is clearance rate equal to renal plasma flow?

A

If a substance is completely cleared

93
Q

What provides a reasonable estimation of renal plasma flow? What percent?

A

PAH clearance (90% cleared)

94
Q

HOw can actual renal plasma flow be calculated?

A

Dividing the PAH clearance rate by PAH extraction rate

PAH clearance/ 0.9

95
Q

How can total blood flow be calculated?

A

Taking the calculated plasma flow and dividing by (1-HCT)

96
Q

Filtration Fraction equation

A

GFR/RPF

97
Q

How to calculate absorption?

A

Filtered load- excretion rate

98
Q

How to calculate secretion?

A

excretion rate- filtered load

99
Q

If equal to inulin clearance….

A

Substance is only filtered, not reabsorbed, not secreted

100
Q

If less than inulin clearance….

A

Substance must be reabsorbed

101
Q

If greater than inulin clearance….

A

Substance must be secreted

Physio II (14 decks)

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