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(J) Physiology Test 3 > Lecture 18 - Tubular Reabsorption and Secretion > Flashcards

Lecture 18 - Tubular Reabsorption and Secretion Flashcards

1
Q

What are the two paths for passive reabsorption into the blood from the kidneys?

L18 S4

A
  • paracellular or transcellular transport across the tubular epithelium
  • transport through the peritubular capillary membrane
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2
Q

What are the three types of aquaporins and where are they located?

L18 S6

A

Aquaporin-1:
-widespread

Aquaporin-2:

  • apical membranes of collecting tubules
  • regulated by ADH

Aquaporin-3:
-basolateral membranes of collecting tubules

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3
Q

What are the primary active transporters located in nephron cell membranes?

L18 S10

A
  • Na+K+ ATPase
  • H+ ATPase
  • H+K+ ATPase
  • Ca+ ATPase
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4
Q

What are the secondary active transporters located in the nephron cell membranes?

L18 S12

A

Sodium glucose co-transporters

SGLT2:
-reabsorbs 90% of glucose in early proximal tubule

SGLT1:
-reabsorbs 10% of glucose in late proximal tubule

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5
Q

What substances are actively secreted into the renal tubules?

L18 S14

A
  • creatinine

- para-aminohippuric acid

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6
Q

What is a transport maximum?

L18 S16

A
  • limit to the rate at which a solute can be transported
  • occurs due to saturation of transport system

-example is glucose which can only be transported at a rate of 375 mg/min

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7
Q

Why do some passively transported substances not have a transport maximum?

L18 S16

A
  • the membrane may be permeable to the substance
  • the rate of diffusion is related to the electrochemical gradient of the substance
  • the fluid containing the substance remains within the tubule
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8
Q

What is solvent drag?

L18 S19

A

-when osmotic movement of water carries solutes with it

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9
Q

What are the transport characteristics of the proximal tubule?

L18 S23-24

A
  • highly metabolic/large number of mitochondria
  • extensive brush borders

Reabsorbs:

  • Na+ (~65%)
  • Cl- (~65)
  • HCO3- (~65%)
  • K+ (~65%)
  • H20
  • glucose (~100%)
  • AAs (~100%)

Secretes:

  • H+
  • organic acids
  • bases
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10
Q

What are the transport characteristics of the thin descending Loop of Henle?

L18 S31-32

A
  • highly permeable to water; ~20% of water is reabsorbed

- secretes most solutes

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11
Q

What are the transport characteristics of the ascending Loop of Henle (both thick and thin)?

L18 S32;34-35

A

Thin ascending loop:
-impermeable to water

Thick ascending loop:

  • impermeable to water
  • reabsorbs K+ (Na+K+ ATPase)
  • reabsorbs Na+, K+, and Cl- (sodium, potassium, chloride co-transporter)
  • reabsorbtion of Mg++ and Ca++ (due to slight leak of K+)
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12
Q

What is the site of action of powerful loop diuretics such as furosemide, ethacrynic acid, and bumetanide?

L18 S35

A

-thick ascending Loop of Henle

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13
Q

What are the transport characteristics of the early distal tubule?

L18 S236;38

A

Early distal tubule:

  • impermeable to water and urea
  • reabsorb Na+, K+, Ca++, and Mg++
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14
Q

What are the transport characteristics of the late distal tubule?

L18 S39-40;41-42

A

Principal cells:

  • reabsorb Na+ and water
  • secrete K+
  • (site of K+ sparing diuretics)

Intercalated cells:

  • reabsorb K+
  • secrete H+
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15
Q

What are the transport characteristics of the medullary collecting duct?

L18 S44-45

A
  • permeability to water controlled by ADH
  • reabsorbs urea
  • reabsorbs Na+, Cl-, and HCO3-
  • excretes H+
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16
Q

What is the source, function, site of action, and stimulus for secretion of aldosterone?

L18 S50

A

Source:
-adrenal cortex

Function:

  • increases sodium reabsorption
  • stimulate potassium secretion

Site of action:
-principal cells of collecting ducts

Stimulus for secretion:

  • increased extracellular potassium
  • increased levels of angiotensin II
17
Q

What are the functions and effects of angiotensin II?

L18 S51

A

Function:

  • increases sodium and water reabsorption
  • returns blood pressure and extracellular volume to normal

Effects:

  • stimulates aldosterone secretion
  • constricts afferent arterioles
  • directly stimulates sodium reabsorption
18
Q

What are the source, function, site of action, and effects of ADH?

L18 S53

A

Source:
-posterior pituitary

Function:
-increases water reabsorption

Site of action:
-late distal tubules, collecting tubules, and collecting ducts

Effects:
-increases formation of cAMP which stimulates movement of aquaporin-2 to membrane

19
Q

What are the source and function of ANP?

L18 S54

A

Source:
-cardiac atrial cells in response to distension

Function:
-inhibits reabsorption of sodium and water

20
Q

What are the source and function of parathyroid hormone?

L18 S55

A

Source:
-parathyroid glands

Function:
-increases calcium reabsorption

21
Q

How is renal clearance calculated?
How is renal clearance to GFR?
Explain why inulin can be used to calculate GFR.

L18 S57-59

A

-the amount of substance cleared from a volume of fluid over a period of time

  • for substances that are fully filtered but not reabsorbed or secreted; renal clearance is equal to GFR
  • Inulin is a polysaccharide not made in the body that fits the criteria listed above

(J) Physiology Test 3 (10 decks)

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