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A&P Fall 24' > AP 18 Nov 24 Lecture 31 > Flashcards

AP 18 Nov 24 Lecture 31 Flashcards

1
Q

How is renal plasma flow determined using PAH?

A

Renal plasma flow is determined by measuring the clearance of PAH (para-aminohippuric acid) and involves comparing venous and arterial concentrations of PAH.

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2
Q

What percentage of PAH is typically removed by the kidneys?

A

The kidneys can remove about 90% of PAH as blood passes through them.

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3
Q

What role does the macula densa play in regulating GFR?

A

The macula densa helps adjust or auto-regulate GFR through the release of renin and nitric oxide, affecting the resistance of afferent and efferent arterioles.

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4
Q

How does angiotensin II affect the arterioles?

A

Angiotensin II preferentially constricts the efferent arteriole while causing relaxation of the afferent arteriole, leading to a reduction in afferent resistance.

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5
Q

What is the effect of drugs that relax blood vessels on GFR?

A

Drugs that relax blood vessels, such as calcium channel blockers and nitric oxide donors, typically preferentially affect the afferent arteriole, which can increase GFR.

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6
Q

What happens to sodium reabsorption in the proximal tubule when angiotensin II binds to its receptors?

A

Angiotensin II binding increases the activity of sodium-potassium ATPase pumps in the proximal tubule, enhancing sodium reabsorption.

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7
Q

How is bicarbonate reabsorbed in the proximal tubule?

A

Bicarbonate is reabsorbed in the proximal tubule primarily through a sodium-bicarbonate symporter, which moves sodium and bicarbonate out of the cell simultaneously.

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8
Q

What is bulk flow in the context of renal physiology?

A

Bulk flow refers to the process of reabsorption in the peritubular capillaries, driven by capillary forces, allowing for significant reabsorption of fluids and solutes.

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9
Q

What is the role of urea in the renal interstitium?

A

Urea helps create a concentrated renal interstitium, facilitating water reabsorption via osmosis.

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10
Q

What are the two pathways for reabsorption in the proximal tubule?

A

Reabsorption occurs through paracellular pathways (between cells) and transcellular pathways (through cell membranes).

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11
Q

What is the role of the renal interstitium in water retention?

A

The renal interstitium helps hold on to as much water as possible by packing solids to assist with osmosis.

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12
Q

What are the pathways involved in substance movement in the kidneys?

A

Substance movement in the kidneys occurs via transcellular pathways, passive diffusion, and paracellular pathways.

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13
Q

What is the function of the brush border in proximal tubular cells?

A

The brush border increases the surface area of proximal tubular cells by about 20 fold, allowing for more transporters to be placed for reabsorption.

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14
Q

How does sodium move into proximal tubular cells?

A

Sodium moves into proximal tubular cells via an electrochemical gradient, which involves both concentration and electrical gradients.

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15
Q

What is the typical membrane potential in the kidney?

A

The typical membrane potential in the kidney is around negative 70 mV.

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16
Q

What happens to chloride concentration in the proximal tubule?

A

Chloride concentration tends to increase slightly as it follows sodium reabsorption, especially in the second half of the proximal tubule.

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17
Q

What is the role of the proximal tubule in protein reabsorption?

A

The proximal tubule reabsorbs about 1.7 grams of the 1.8 grams of protein filtered daily, using endocytosis to manage small amounts of filtered proteins.

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18
Q

What is endocytosis in the context of proximal tubular cells?

A

Endocytosis is the process by which proximal tubular cells engulf filtered proteins, breaking them down into amino acids for reabsorption.

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19
Q

How does the proximal tubule regulate acid-base balance?

A

The proximal tubule regulates acid-base balance primarily through the sodium-proton exchanger, which secretes protons and reabsorbs sodium.

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20
Q

What is the role of carbonic anhydrase in the proximal tubule?

A

Carbonic anhydrase facilitates the conversion of carbonic acid into carbon dioxide and water, aiding in bicarbonate reabsorption and pH regulation.

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21
Q

What is formed in the proximal tubule?

A

A bunch of carbonic acid is formed in the proximal tubule.

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22
Q

What role does carbonic anhydrase play in the proximal tubule?

A

Carbonic anhydrase speeds up the reaction of carbonic acid dissociating into CO2 and water.

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23
Q

What happens if the reaction of carbonic acid goes in the opposite direction?

A

Carbonic acid can dissociate into protons and bicarbonate.

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24
Q

What is the effect of carbonic anhydrase inhibitors?

A

They slow down the proton-sodium exchanger, leading to decreased bicarbonate reabsorption and potential acidosis.

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25
Q

What is the function of glutamine in the proximal tubule?

A

Glutamine is converted into bicarbonate and ammonium, helping to balance acid-base status.

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26
Q

How is bicarbonate produced in the proximal tubule?

A

One glucose molecule is converted into two bicarbonate molecules and two ammonium molecules.

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27
Q

What is the role of sodium phosphate in urine?

A

Sodium phosphate acts as a buffer for protons in urine.

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28
Q

How is calcium reabsorbed in the proximal tubule?

A

Calcium is reabsorbed through paracellular and transcellular pathways, often dragged along with water.

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29
Q

What regulates calcium levels in the body?

A

The parathyroid gland monitors calcium levels and releases parathyroid hormone (PTH) when levels are low.

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30
Q

What are the effects of parathyroid hormone (PTH)?

A

PTH increases calcium reabsorption in the kidneys, activates vitamin D3 for dietary absorption, and stimulates bone breakdown.

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31
Q

What happens to bone density during chronic hypocalcemia?

A

Chronic hypocalcemia can lead to osteoporosis due to increased bone breakdown and decreased bone building.

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32
Q

What are osteoblasts?

A

Osteoblasts are bone builders that increase bone density by taking calcium and phosphate and forming bone.

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33
Q

What happens if there is a calcium deficit?

A

Bone building activity by osteoblasts is inhibited while bone breakdown is stimulated.

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34
Q

What is the role of PTH?

A

PTH increases osteoclast activity (bone breakdown) and decreases osteoblast activity (bone building).

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35
Q

What happens to PTH levels when calcium levels are high?

A

PTH levels should be low, leading to reduced osteoclast activity and increased osteoblast activity.

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36
Q

How can we rebuild bones?

A

Taking calcium supplements can help reinforce bones, provided calcium is reabsorbed.

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37
Q

What happens with long-term calcium deficit?

A

It can lead to porous bones that are more likely to fracture.

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38
Q

What is the function of the proximal tubule?

A

The proximal tubule secretes organic compounds and is involved in the reabsorption of substances.

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39
Q

What are the two basic categories of organic compounds handled by the kidney?

A

Organic cations and organic anions.

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40
Q

What are examples of endogenous organic anions?

A

Bile salts, purates, urate, oxalate.

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41
Q

What are examples of exogenous organic anions?

A

Drugs such as penicillin and salicylates.

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42
Q

What are examples of endogenous organic cations?

A

Acetylcholine, creatine, dopamine, epinephrine.

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43
Q

What are examples of exogenous organic cations?

A

Isoproterenol, atropine, morphine, quinine.

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44
Q

How are organic cations removed from the proximal tubule?

A

Via a proton-dependent antiporter system.

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45
Q

How are organic anions removed from the proximal tubule?

A

Via a sodium-dependent process involving alpha-ketoglutarate.

46
Q

What is the significance of alpha-ketoglutarate in organic anion transport?

A

It helps concentrate in proximal tubular cells and facilitates the exchange with organic anions.

47
Q

What is the general rule of thumb for reabsorption in the proximal tubule?

A

About two-thirds of most substances are reabsorbed in the proximal tubule.

48
Q

What is the loop of Henle?

A

A U-shaped loop in the nephron that consists of descending and ascending limbs.

49
Q

What occurs in the thin descending limb of the loop of Henle?

A

Water is reabsorbed as tubular fluid moves into a more concentrated environment.

50
Q

What occurs in the thin ascending limb of the loop of Henle?

A

It is relatively impermeable to water and primarily reabsorbs sodium and chloride.

51
Q

What is the permeability of the thin ascending limb of the loop of Henle?

A

The thin ascending limb of the loop of Henle is relatively impermeable to water.

52
Q

What transporter is present in the thin ascending limb of the loop of Henle?

A

A sodium chloride transporter reabsorbs sodium and chloride from the tubular fluid.

53
Q

What type of transporter is the sodium chloride transporter in the thin ascending limb?

A

It is a primary active transporter driven by ATP.

54
Q

What happens to the ascending limb of the loop of Henle as it widens?

A

It becomes the thick ascending limb, which is still relatively impermeable to water.

55
Q

What ions are reabsorbed in the thick ascending limb of the loop of Henle?

A

Magnesium and calcium are reabsorbed via a paracellular route.

56
Q

What role does potassium play in the reabsorption of magnesium and calcium?

A

Potassium channels allow potassium to leak back into the tubular fluid, creating a positive charge that helps push magnesium and calcium to be reabsorbed.

57
Q

What is the electrical charge in the tubular fluid at the thick ascending limb?

A

The charge is positive 8 millivolts, which aids in the reabsorption of divalent cations.

58
Q

What is the function of sodium-potassium pumps in the thick ascending limb?

A

They help maintain acid-base balance and facilitate ion transport.

59
Q

What is the significance of loop diuretics?

A

Loop diuretics inhibit the transporter in the thick ascending limb, reducing the concentration of the renal interstitium.

60
Q

What is the maximum osmolarity of the renal interstitium?

A

The maximum osmolarity is about 1200 mOsm/L, which reflects the kidney’s ability to conserve water.

61
Q

What hormone influences calcium reabsorption in the distal tubule?

A

Parathyroid hormone (PTH) increases the number of calcium channels in the distal tubule.

62
Q

What type of diuretics affect calcium reabsorption in the distal tubule?

A

Thiazide diuretics inhibit sodium and chloride reabsorption in the distal tubule.

63
Q

What cells in the distal tubule are sensitive to aldosterone?

A

Principal cells are sensitive to aldosterone and influence sodium reabsorption and potassium secretion.

64
Q

How does aldosterone affect potassium and sodium in the distal tubule?

A

Aldosterone speeds up potassium secretion into the tubule and increases sodium reabsorption.

65
Q

Cellular extensions on the tubular lumen side that increase surface area and allow for more efficient/increased amount of transporters.

A

Brush Borders

66
Q

What is the charge inside the tubular epithelial cells?

A

Intercellular space charge is -70mV

67
Q

What is the charge within the tubular lumen (Lecture references PCT)

A

PCT charge is -3mV

68
Q

What is significant about Cl- transport in the PCT?

A

There is a Cl- time lag as it follows Na+ since there are no dedicated transporters in the PCT

69
Q

Does Na+ build up concentration within the PCT?

A

No, Na+ doesn’t usually build up in PCT but Cl- does so it is drawn in (reabsorbed) with Na+ even through there aren’t any specific transporters.
* There is a significant uptick in Cl- in the later half of PCT

70
Q

On average, how much protein do the kidneys filter per day?

A

1.8g of protein filtered each day (in healthy patient)
* 1.7g protein reabsorbed (this is the MAX reabsorption capacity)
so 100mg leftover in urine

71
Q

How much protein is typically urinated out per day?
Is this enough to cause cloudiness?

A

100mg of protein is left in urine each day and should NOT make urine cloudy (that is something else or protein wasting and both are bad)

72
Q

How do filtered proteins return to the body? (Why do we only urinate out 100mg of the 1.8g of filtered proteins?

A

Proteins are pulled into PC Tubular cells via endocytosis (AKA pinocytosis). They are then broken down/converted into their amino acid forms and stored in the renal interstitium for future use and to increase renal interstitium osmolarity

73
Q

T/F, Endocytosis/pinocytosis can happen throughout the nephron to help reduce protein wasting.

A

False, endocytosis/pinocytosis can ONLY happen in PCT

74
Q

What is the ratio for the sodium/proton (NHE) in the PCT?

A

NHE rate is 1:1 and is the most prominent path for Na reuptake in the PCT!

75
Q

Ratio of H+ and HCO3- to make carbonic acid

A

Proton to bicarb H2CO3 ratio is 1:1

76
Q

In the PCT, does carbonic anhydrase convert carbonic acid into (HCO3- and H+) or (CO2 and H20)?

A

In PCT, CA converts H2CO3 into CO2 and H2O so they can diffuse into PC tubular cells.

77
Q

In the Proximal convoluted tubular cell, does carbonic anhydrase convert carbonic acid into (HCO3- and H+) or (CO2 and H20)?

A

In the proximal convoluted tubular cell, CA converts H2CO3 into HCO3- and H+ so bicarb can be reabsorbed into the body (via renal interstitium/peritubular capillaries) and protons can be secreted back into the PCT for either excretion from the body or recycling into more carbonic acid.

78
Q
A

In Tubular cell, CA drives bicarb and proton conversion from H2CO3

79
Q
A

CA Inhibition slows down NA+H+ Exchanger which will lead to less bicarb reabsorption. This will lead to less bicarb in the system and eventually acidosis

80
Q
A

Proximal tubular cell break down glutamine into 2(HCO3-) and 2(NH4+). There is an ammonium/sodium ATP pump in the proximal tubular cell to remove the ammonium and excrete it in the urine

81
Q
A

Most of our bicarb is produced in the PCT by glutamine conversion

82
Q
A

There are a total of 4 molecules made from a single glutamine molecule (X2 bicarb and X2 ammonium)

83
Q
A

Phosphate is a good buffer for H+

84
Q
A

Calcium gets dragged alongside water into the renal interstitium via paracellular junctions and Ca channels in proximal tubular cells

85
Q

What type of channel is the calcium transporter in the PCT?

A
86
Q
A

3:1 NCE in PCT cell to get Ca into renal interstitium

87
Q
A

CA ATP Pump to get Ca into renal interstitium

88
Q
A

parathyroid gland monitors calcium levels and can increase reuptake of Ca in PCT via PTH

89
Q
A

PTH can also increase D3 activation

90
Q
A

Osteoclasts break down bones and increase in activity from PTH.
* PTH inhibits osteoblast activity

91
Q
A

Hypocalcemia leads to osteoporosis

92
Q
A

Long-term calcium storage is in the bones

93
Q
A

Slide 24 renal cont’d pic Organic cations (Handled by H+ Dependent Antiporter)

94
Q
A

Slide 25 renal cont’d pic Organic anions (Handled by Na+ Dependent Antiporter)
* Also, Alpha-Keto Gluterate (aKG) needed for anion transfer.

95
Q
A

Picture from Lange Book Figure 5-2

96
Q
A

First person to take PCN was 1942

97
Q
A

Approximately 2/3 of everything is absorbed in the PCT, especially water

98
Q
A

Hippurates use the same transporter as PCN so adding synthetic hippurates=more PCN in circulation (through competitive antagonism)

99
Q
A

TAL relatively impermeable to water

100
Q
A

NaCl transporter in TAL is the most important.
* It is a primary active transporter (dependent on ATP)

101
Q

Primary ions reabsorbed in TAL

A

NA+, K+, Mg++, and Ca++ (Through paracellular diffusion)

102
Q

Unique feature of TAL in the loop of Henle?

A

TAL tubular lumen is +8mV (Helps push positive cations back into renal interstitium via paracellular diffusion)

103
Q
A

NaCCK pump moves 4 ions (1Na, 2Cl, and 1K) into tubular cell of TAL

104
Q
A

Loop diuretics shut down NCCK pump
* Considered most powerful (potent) diuretic class because it dilutes the renal interstitium!

105
Q
A

1200mOsm is the maximum concentration of renal interstitium

106
Q

What is the maximum urine concentration (in mOsm)

A

1200mOsm because that is as concentrated as our renal interstitium can get

107
Q

How concentrated can desert lizards make their urine?

A

Desert lizards can concentrate their urine to 3000 mOsm

108
Q
A

1:1 ratio of Na and Cl in DCT transporter (Blocked by thiazides)

109
Q

Hormones that DCT is sensitive to?

A

ADH and Aldosterone
* Aldo sensitive cells are called principal cells
*ADH sensitive cells are intercalate cells

110
Q

Heavy filtration of the glomerular capillaries + Heavy reabsorption at the peritubular capillaries = what?

A

Bulk Flow

A&P Fall 24' (27 decks)

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