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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
How does capillary surface area relate to filtration coefficient and reabsorption?
Increased surface area Increased filtration coefficient Increased reabsoprtion
26
How does capillary permeability relate to filtration coefficient and reabsorption?
Increased permeability Increased filtration coefficient Increased reabsorption
27
How much does the filtration coefficient change under most conditions? What can affect it?
Coefficient remains constant under most physiologic conditions. Will be affected by renal disease.
28
Autoregulation works to keep what constant as pressure changes?
GFR and RBF
29
Under what pressure range does autoregulation work?
75 mmHg to 160 mmHg
30
Even though autoregulation is involved, there is a small increase in _______, which results in an increase in _________.
GFR; urine output
31
Arterial pressure increase = Small ______ in the amount of sodium and water reabsorbed.
decrease
32
Small increase in peritubular capillary hydrostatic pressure= _______ renal interstitial hydrostatic pressure = _______backflow of solute and water
Increased; increased
33
Arterial Pressure increases= Angiotensin II ________.
decreased
34
Decreased Angiotensin II = less stimulation of what?
Sodium reabsorption | Aldosterone production; less stimulation of sodium reasborption
35
Kidneys must be able to respond to changes in _______ of specific substances without changing ______ of the substances.
Intake; output
36
What provides the control specificity needed to maintain normal body fluid volumes and solute concentrations?
Hormone secretion
37
Aldosterone: Site of Action; Effects
Site of Action: Collecting duct/tubule Effects: increased NaCl, H20 reabsorption Increased K+ secretion
38
Angiotensin II: Site of Action; Effects
Site of Action: Proximal tubule; thick ascending loop of henle/distal tubule; collecting duct Effects: Increased NaCl, H20 reabsorption Increased K+ secretion
39
ADH: Site of Action; Effects
site of action: distal tubule; collecting tubule and duct | effects: increased H20 reabsorption
40
Atrial natriuretic peptide: Site of Action; effects
Site of action: distal tubule; collecting tubule and duct | Effects: decreased NaCl reasborption
41
Parathyroid hormone: Site of action; effects
Site of action: proximal tubule; thick ascending loop of henle; distal tubule Effects: decreased PO4-- reabsorption Increased Ca++ reasborption
42
What secretes aldosterone?
Zona glomerulosa in adrenal cortex
43
What is the function of aldosterone?
Regulates sodium reabsorption and potassium secretion; very important regularly of [K+]
44
What is the principal site of action of aldosterone?
Principal cells of cortical collecting tubule; stimulates increased Na-K ATPase activity (basolateral locations) Increases permeability of luminal side membrane to sodium
45
What stimulates increased release of aldosterone?
Increased extracellular potassium concentration | Increased angiotensin II levels (sodium/volume depletion or low arterial pressure)
46
What disease is the absence of aldosterone?
Addison's disease; adrenal malfunction or destruction
47
What disease is an excess of aldosterone?
Adrenal tumors; Conn's syndrome
48
What is the most powerful sodium-retaining hormone?
Angiotensin II
49
What causes increased production of angiotensin II?
Low blood pressure and/or low ECF volume
50
Angiotensin II stimulates the secretion of what?
Aldosterone; resulting in increased sodium reabsorption
51
What is angiotensin II's effect on the efferent arterioles?
Constricts efferent arterioles; increased sodium and water reabsorption
52
What is the purpose of angiotensin II constricting effect arterioles?
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
Angiotensin II directly stimulates sodium reabsorption where?
Proximal tubules, loop of henle, distal tubules, and collecting tubules.
54
Angiotensin II stimulates which pumps?
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
Angiotensin II affects transport on which membranes?
Luminal and basolateral membranes
56
Where is angiotensin II "very active"
proximal tubule
57
What is vasopressin?
ADH
58
Where is ADH made?
Hypothalamus
59
Two types of _______ produce ADH.
Magnocellular (large) neurons
60
Where are the neurons located that make ADH?
Supraoptic (87%) and paraventricular (17%) nuclei (hypothalamus)
61
What happens to ADH once it is produced?
Moves down the neurones to their tips which are located in the posterior pituitary
62
Where is ADH released?
Neurons in the posterior pituitary
63
How is ADH released?
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
Decreased ADH = ______ water permeability= _______ urine volume and _____solute
decreased, increased, decreased; results in large volumes of dilute urine
65
ADH stimulates the formation of water channels where?
Across the luminal membrane
66
What does ADH bind with? What does this do?
Specific V2 receptors; increases formation of cyclic AMP and activation of protein kinases
67
What does protein kinase activation result in?
Movement of aquaporin-2 to luminal side of cell
68
Aquaporin-2
intracellular protein
69
What do aquporin-2's do?
Come together and fuse with cell membrane to from water channels which increases membrane permeability to water (increases water reabsorption)
70
What increases the formation of aquaporin-2 molecules?
Chronic increases in ADH
71
AVP
arginine vasopressin
72
Where are V2 receptors?
Basolateral membranes
73
Increased ADH in the plasma results in movement of ADH from where to where?
From peritubular capillaries to renal interstitial space
74
WHat provides water channels on the basolateral membrane?
aquaporins; no evidence to show that they are affected by [ADH]
75
What does decreased ADH result in as far as the aquaporin-2?
Movement of the aquaporin-2 molecules back into the cytoplasm which reduces the number of water channels and decreased water permeability
76
Where is atrial natriuretic peptide secreted?
Cardiac atrial cells when atria distended by plasma volume expansion
77
What is the action of atrial natriuretic peptide?
Direct inhibition of sodium and water reabsorption (especially collecting ducts) Inhibits renin secretion (thus inhibits angiotensin II formation)
78
What is an important response to help prevent sodium and water retention during heart failure?
Atrial natriuretic pepide
79
What is the most important hormone for regulating calcium?
Parathyroid hormone
80
What is the action of parathyroid hormone?
Increases calcium reabsorption (distal tubules) INhibits phosphate reabsorption (proximal tubule) Increases magnesium reabsorption (loop of henle)
81
Severe SNS stimulation = _________(constriction/dilation) of renal arterioles= ______ GFR
Constriction of renal arterioles, decreases GFR
82
Low levels SNS stimulation activate what?
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
SNS stimulates the release of what ?
Renin (angiotensin II) which adds to increase in tubular reabsorption of sodium
84
Renal clearance
volume of plasma that is completely cleared by kidneys per unit time
85
Why is renal clearance not realistic?
No volume of blood completely cleared
86
Renal clearance provides what?
``` Way to quantify excretory function of kidneys Quantify RBF Quantify glomerular filtration Qunatify tubular reabsoprtion Quantify tubular secretion ```
87
What is the equation for renal clearance?
``` 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
Clearance of what should be equal to GFR?
Inulin
89
When is the excretion rate the filtration rate?
Solute is freely filtered and neither reabsorbed nor secreted
90
How much of creatinine is reabsorbed?
Small amount
91
How do you make a rough estimate of changes in GFR?
Look at changes in creatinine concentration; a four fold increase in creatinine concentration means the GFR is one-fourth normal
92
When is clearance rate equal to renal plasma flow?
If a substance is completely cleared
93
What provides a reasonable estimation of renal plasma flow? What percent?
PAH clearance (90% cleared)
94
HOw can actual renal plasma flow be calculated?
Dividing the PAH clearance rate by PAH extraction rate | PAH clearance/ 0.9
95
How can total blood flow be calculated?
Taking the calculated plasma flow and dividing by (1-HCT)
96
Filtration Fraction equation
GFR/RPF
97
How to calculate absorption?
Filtered load- excretion rate
98
How to calculate secretion?
excretion rate- filtered load
99
If equal to inulin clearance....
Substance is only filtered, not reabsorbed, not secreted
100
If less than inulin clearance....
Substance must be reabsorbed
101
If greater than inulin clearance....
Substance must be secreted

Physio II (14 decks)

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