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Renal-Chapter 28 Flashcards

1
Q

Which has a larger value, filtration and reabsorption or urinary excretion?

A

Filtration and reabsorption

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2
Q

Which is more selecitve filtration or reabsorption?

A

Filtration is relatively non-selective

Reabsorption is highly selective

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3
Q

For a substance to be reabsorbed, what are two things it must do?

A

1-Travel across tubular epithelial membrane into renal interstitial fluid

THEN

2-Travel through peritubular capillary membrane into blood

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4
Q

Transcellular route vs paracellular route

A

Transcellular route
Solutes travel through cell membranes of tubular cells into interstitial fluid.
(example=water)

Paracellular route
Solutes travel through spaces between cell junctions of tubular cells into interstitial fluid.

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5
Q

Can Na+ move through transcellular route or paracellular route?

A

BOTH routes

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6
Q

Explain how Na+ moves transceullarly via active transport

A

On basolateral side of of tubular epithelial cell there are extensive Na/K ATPase pumps that pump Na into interstitial fluid and K into tubular epithelial cell. Requires E.

Due to low concentration of Na in tubular epithelial cells, Na is able to passively diffuse into the tubular epithelial (LOW Na) from tubular lumen (HIGH Na).

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7
Q

What is transport maximum

A

The limit to the rate at which a solute can be transported.

When this limit is reached, there can not be any more reabsorbtion and whatever is not reabsorbed will be secreted and excreted in urine.

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8
Q

What does it mean if glucose has reached its threshold during transport?

Example

A

The amount of glucose that has been filtered has reached a point where not all of it will be reabsorbed. The excess glucose will be excreted in urine.

See in diabetes mellitus. There’s so much glucose that it is not reabsorbed in the blood and you will see glucose in urine.

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9
Q

Where does water move as solutes move?

A

Water moves (passively) where ever the solutes go due to osmosis.

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10
Q

As Na+ (and H2O )moves to be reabsorbed into the blood, what does that do to the lumen?

A

Leaves with a (-) charge since Na+ is leaving.

This creates a urea gradient that favors reabsorption. Urea travels passively through urea transporters.

Cl- also increases in lumen and travels paracellularly and passively.

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11
Q

Proximal Tubular reabsorption percentage

  • What’s reabsorbed?
  • What;s secreted?
A

Proximal tubules reabsorb 65 percent of filtered: Na+, Cl-, HCO3-, K+

Reabsorb essentially all filtered glucose and AA

Secretes organic acids, bases, and H+ into tubular lumen.

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12
Q

What are special features of the proximal tubule?

A

Has apical microvilli to increase SA (helps reabsorption)

Also, lots of mitochondria to provide E for active transport.

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13
Q

Generally, why doesn’t osmolarity change in proximal tubule?

A

Because water follows solutes

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14
Q

In proximal tubules, what would it mean if tubular fluid/plasma concentration ratio was less than one? Greater than one?

A

Less than 1
Substance is transported at rates higher than water- everything is reabsorbed
See with glucose and AA

Greater than 1
Transport is slower than water.
See with creatinine.

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15
Q

What type of diffusion is seen in the thin descending segment? Why?

A

Simple diffusion

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16
Q

What is reabsorbed at descending LOH?

A

Highly permeable to water (20 percent of filtered water is reabsorbed here)

Moderately permeable to most solutes (urea, Na+)

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17
Q

Are there are a lot of mitochondria in descending LOH?

A

Few

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18
Q

Is there active reabsorption at descending LOH?

A

Little to no

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19
Q

Ascending thin LOH permeability

A

IMPERMEABLE TO WATER

Permeable to Na+ and urea

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20
Q

Ascending thick LOH permeability

A

IMPERMEABLE TO WATER

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21
Q

Ascending thick LOH reabsorption

A

Reabsorption of about 25 percent of filtered Na+, Cl-, K+ and Ca2+, HCO3-, and Mg2+

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22
Q

Does ascending LOH secrete anything?

A

H+ into tubular lumen

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23
Q

What happens to the tubular fluid in the Thick Ascending LOH?

A

Fluid becomes very dilute and in a hypoosmotic environment

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24
Q

How does Na+, Cl-, and K+ transported into tubular cells in the thick ascending LOH?

  • Ratio
  • Prevents
A

Na+/Cl-/K+ Co-transporter in luminal membrane (Opposite side of Na+/K+ ATPase pump.

Pumps in 1:2:1 ratio respectively.

Prevents reabsorption of Na+ if Na/Cl/K transporter is inhibted

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25
Counter transport active in thick ascending LOH
Na+/H+ counter transporter Na+ transported into tubular cell while H+ transported into tubular lumen
26
Due to slight positive charge in lumen during filtrate flow in thick ascending LOH, what happens?
Positive elements like Na+, K+, Mg2+, and Ca2+ travel paracellularly into the interstitial fluid
27
Where is the site of action for loop diuretics?
Furosemide, ethacrynic acid, bumetanide Thick ascending LOH...they'll inhibit Na/Cl/K co-transporter. This will allow more solutes to stay in the tubular lumen and cause H20 to stay in lumen.
28
``` Of the following, where is there active NaCl transport? Proximal Tubule Thin descending LOH Thin ascending LOH Thick ascending LOH ```
Proximal tubule Thick ascending LOH
29
``` Of the following, where is water permeable? Proximal Tubule Thin descending LOH Thin ascending LOH Thick ascending LOH ```
Proximal tubule Thin descending LOH
30
``` Of the following, where is NaCl permeable? Proximal Tubule Thin descending LOH Thin ascending LOH Thick ascending LOH ```
Proximal tubule Thin descending LOH Thin ascending LOH
31
``` Of the following, where is ureae permeable? Proximal Tubule Thin descending LOH Thin ascending LOH Thick ascending LOH ```
Proximal tubule Thin descending LOH Thin ascending LOH
32
What important region is located inbetween the efferent/afferent arterioles and the early distal convoluted tubule?
Macula densa
33
The early distal tubule is similar to what section? How?
Similar to thick ascending LOH Reabsorbs Na+, Cl-, Ca2+, and Mg2+ IMPERMEABLE TO WATER AND UREA
34
Early distal tubule is also known as the
Diluting segment
35
How are the ascending thick LOH and early distal tubule different. How?
How they reasborb Na+ Reabsorbs about 5 percent of filtered Na+
36
What pumps/means of transportation are observed in the early distal tubule?
Na+/K+ ATPase ( transports Na+ into interstitial fluid) Na+/Cl- co transporter (transports Na+ from lumen into tubular cells). Cl- can diffuse into interstitial fluid via Cl- channels
37
What can inhibit Na+/Cl- co-transporter in early distal tubule?
Thiazide diuretics
38
What are the two types of cells in the late distal tubules and cortical collecting tubules
Principal cells Intercalated cells
39
What do prinicipal cells do? | -controlled by
Reabsorb Na+ and secrete K+ into the lumen | aldosterone control
40
What do intercalated cells do?
Reabsorb K+ and HCO3- from the lumen and secrete H+ into the lumen.
41
What controls the reabsorption of water in the late distal tubule and cortical collecting tubule?
Anti-diuretic hormones (ADH, AVP)
42
What stimulates secretion of aldosterone? What is the effect?
Angiotensin II (secretes when low Na+; high ECF K+, and volume depletion) When aldosterone is released, there is an increase in Na+ and water reabsorption. There's also an increase in K+ secretion. - Stimulates basolateral Na+/K+ ATPase - Increases expression of luminal Na+ channels
43
What is aldosterone?
Adrenal secreted mineralocorticoid
44
What do K+ sparing diuretics do?
Inhibit stimulation of Na+ reabsirption and K+ secretion Increases water excretion
45
K+ sparing diuretics are an antagonist to
Aldosterone Directly competes with aldosterone for receptors
46
K+ sparing diuretics inhibit what
Indirectly inhibits Na+ channel. | Inhibits Na+/K+ ATPase by blocking Na+ reabsorption from lumen
47
What are some K+ sparing diuretics that are aldosterone anatgonists?
Spironolactone Eplerenone
48
What are some K+ sparing diuretics that are Na+ channel blockers?
Amiloride Triamterene
49
What cells are important for acid-base regulation?
Intercalated cells (30-40 percent of CT and CD cells)
50
What are the different types of intercalated cells?
Type A= eliminates H+ and reabsorbs HCO3- in acidosis Type B= reabsorbs H+ and secretes HCO3- in alkalosis
51
In late distal tubules and cortical collecting tubules, what controls the permeability of water?
ADH - high ADH= tubular segments permeable to H2O - absence of ADH, impermeable to H2O - Diluting and concentrating urine
52
Medullary collecting ducts - Reabsorb - Secrete - Permeability
Reabsorbs less than 10 percent of filtered H2O and Na+ Actively reabsorbs Na+ Secretes H+ ions (acid-base balance) Permeable to urea (urea transporters present)
53
What is the last segment with urine processing ability?
Medullary collecting ducts
54
In medullary collecting ducts, what controls the reabsorption of water?
ADH
55
``` Of the following sections, which has active NaCl transport? proximal tubule thin descending LOH thin ascending LOH thick ascending LOH distal tubule cortical collecting tubule inner medullary collecting duct ```
All except thin descending LOH and thin ascending LOH Proximal tubule and thick ascending LOH have more
56
``` Of the following sections, which are permeable to H20. Permeable with ADH proximal tubule thin descending LOH thin ascending LOH thick ascending LOH distal tubule cortical collecting tubule inner medullary collecting duct ```
H20 permeable Proximal tubule Thin descending LOH ADH Distal tubule Cortical collecting tubule Inner medullary collecting duct
57
``` Of the following sections, which are permeable to NaCl proximal tubule thin descending LOH thin ascending LOH thick ascending LOH distal tubule cortical collecting tubule inner medullary collecting duct ```
Proximal tubule Thin descending LOH Thin ascending LOH
58
``` Of the following sections, which are permeable to urea? proximal tubule thin descending LOH thin ascending LOH thick ascending LOH distal tubule cortical collecting tubule inner medullary collecting duct ```
Proximal tubule Thin descending LOH Thin ascending LOH With ADH Inner medullary collecting duct
59
As glomerular filtrate passes through tubule, what percent of water gets reabsorbed?
99 (and most solutes)
60
What forces determine rate of reabsorption in peritubular caps?
Hydrostatic and colloid osmotic pressure
61
For peritubular capillaries | If you increase arterial pressure what will happen to hydrostatic pressure and reabsorption?
Increase peritubular hydrostatic pressure Decrease reabsorption
62
If you increase resistance of afferent and efferent arterioles, what happens to peritubular capillary and reabsorption?
Capillary pressure will decrease Reabsorption will increase
63
What are the 2 major forces that regulate capillary hydrostatic pressure?
Arterial pressure Resistance of afferent and efferent arterioles
64
What effects does systemic colloid osmotic pressure have on peritubular capillaries?
Increase in plasma protein concentration will increase colloid osmotic pressure in peritubular capillaries and increase reabsorption
65
If filtration fraction is increased with the peritubular capillaries, what happens to reabsorption?
Reabsorption in the peritubular capillaries will increase when there's an increase in filtration fraction.
66
T/F Generally, forces that increase peritubular capillary reabsorption also decreases renal tube reabsorption
F Increase in peritubular capillary reabsorption has increase in renal tubule reabsorption
67
Hemodynamic changes that decrease peritubular capillary reabsorption will do what to tubular reabsorption?
Decrease
68
The colloid osmotic pressure of peritubular capillaries are determined by
Systemic plasma colloid osmotic pressure Filtration fraction
69
Aldosterone - Site of action - Effects
Collecting tubule and duct Increase NaCl Increase H2O reabsorption Increase K+ secretion
70
Angiotensin II - Site of action - Effects
Proximal tubule, thick ascending LOH, distale tubule, collecting tubule Increase NaCl Increase H2O reabsorption Increase H+ secretion
71
ADH - Site of action - Effects
Distal tubule, collecting tubule and duct Increase H2O reabsorption
72
Atrial natriuretic peptide - Site of action - Effects
Distal tubule, collecting tubule and duct Decrease NaCl reabsorption
73
Parathyroid hormone - Site of action - Effects
Proximal tubule, thick ascending LOH, distal tubule Decrease PO4 reabsorption Increase Ca2+ reabsorption
74
T/F Aldosterone increases Na+ reabsorption and stimulates K+ reabsorption
F Increases Na+ reabsorption K+ secretion
75
What are zona glomerulose cells
In the adrenal cortex Secrete aldosterone
76
Principal cells of late distal tubules and cortical collecting ducts when aldosterone present does 3 things
-Stimulates Na+/K+ ATPase on basolateral membrane Increases Na+ permeability on luminal membrane Increases K+ secretion into tubular fluid
77
What are stimuli for secretion when aldosterone is present?
Increased extracellular K+ concentration Angiotensin II
78
What is Conn's Syndrome
Excessive amount of aldosterone secretion - Na+ retention - Decreased plasma K+ concentration due to xs K+ secretion
79
What is Addison's disease
No aldosterone secretion - Loss of Na+ from body - Accumulation of K+ in ECF
80
What is the body's most powerful salt-retaining hormone?
Angiotensin II
81
Renin release is stimulated by (2) | -Give examples
Low blood pressure or low ECF volume Hemorrhage Severe diarrhea
82
What is the mechansm to increase salt and water reabsorption with angiotensin II
Aldosterone is released Constriction of efferent arterioles - Decreases hydrostatic pressure of peritubular capillaries - Increase colloid osmotic pressure in peritubular capillaries Stimulate Na+ reabsorption
83
Angiotensin II stimulates Na+ reabsorption where?
Proximal tubule LOH Distal tubule Collecting tubule
84
Angiotensin II stimulates what in the luminal membrane and tubular cell?
Na+/H+ exchange Stimulates Na+/K+ ATPase Stimulates Na+/HCO3- cotransport on basolateral membrane
85
ADH or Arginine vasopressin increases water permeability where
DT CT CD
86
How does ADH work?
Binds to V2 receptors Stimulates production of cAMP Apical membrane insertion of water channels Water travels down concentration gradient and is rapidly reabsorbed
87
How does Atrial natriuretic peptide work?
Increased plasma volumed causes atria to release ANP Water and Na+ reabsorption in inhibited in the CD Increased urine excretion and decreased blood volume (Dangerous when congestive heart failure when atria are stretched)
88
How does parathyroid horome
Low extracellular concentration of free Ca2+ causes realease of parathyroid hormone from parathyroid gland Increase Ca2+ reabsorption in thick ascending LOH and DT Inhibits PO4 reabsorption Stimulates Mg2_ reabsorption
89
How can sympathetic nervous system increase Na+ reabsorption
Strong sympathetic nervous system can constrict the afferent and efferent arteriole to reduce GFR. Low levels of sympathetic activity will increase Na+ reabsorption in the PT and LOH (noepinephrine->alpha adrenergic receptor) Sympathetic nervous system activation increases renin release and angiotensin II formation

Physiology (18 decks)

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